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  • Time to sound the alarm about the hidden epidemic of kidney disease

    Time to sound the alarm about the hidden epidemic of kidney disease

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    Coloured 3D computed tomography scan of healthy human kidneys.

    Kidney disease is growing worldwide. The secretariat of the World Health Organization has welcomed the call to include it as a non-communicable disease that causes premature deaths.Credit: Vsevolod Zviryk/SPL

    A quiet epidemic is building around the world. It is the third-fastest-growing cause of death globally. By 2040, it is expected to become the fifth-highest cause of years of life lost. Already, 850 million people are affected, and treating them is draining public-health coffers: the US government-funded health-care plan Medicare alone spends US$130 billion to do so each year. The culprit is kidney disease, a condition in which damage to the kidneys prevents them from filtering the blood.

    And yet, in discussions of priorities for global public health, the words ‘kidney disease’ do not always feature. One reason for this is that kidney disease is not on the World Health Organization (WHO) list of priority non-communicable diseases (NCDs) that cause premature deaths. The roster of such NCDs includes heart disease, stroke, diabetes, cancer and chronic lung disease. With kidney disease missing, awareness of its growing impact remains low.

    Chronic kidney disease and the global public health agenda: an international consensus

    The authors of an article in Nature Reviews Nephrology this week want to change that (A. Francis et al. Nature Rev. Nephrol. https://doi.org/10.1038/s41581-024-00820-6; 2024). They are led by the three largest professional organizations working in kidney health — the International Society of Nephrology, the American Society of Nephrology and the European Renal Association — and they’re urging the WHO to include kidney disease on the priority NCD list.

    This will, the authors argue, bring attention to the growing threat, which is particularly dire for people in low- and lower-middle-income countries, who already bear two‑thirds of the world’s kidney-disease burden. Adding kidney disease to the list will also mean that reducing deaths from it could become more of a priority for the United Nations Sustainable Development Goals target to reduce premature deaths from NCDs by one-third by 2030.

    As of now, rates of chronic kidney disease are likely to increase in low- and lower-middle-income countries as the proportion of older people in their populations increases. Inclusion on the WHO list could provide an incentive for health authorities to prioritize treatments, data collection and other research, along with funding, as with other NCDs.

    Kidney disease often accompanies other conditions that do appear on the NCD list, such as heart disease, cancer and diabetes — indeed, kidney-disease deaths caused specifically by diabetes are on the list. But the article authors argue that “tackling diabetes and heart disease alone will not target the core drivers of a large proportion of kidney diseases”. Both acute and chronic kidney disease can have many causes. They can be caused by infection or exposure to toxic substances. Increasingly, the consequences of global climate change, including high temperatures and reduced availability of fresh water, are thought to be contributing to the global burden of kidney disease, as well.

    Light micrograph of the kidney glomerulus

    The kidney glomerulus filters waste products from the blood. In people with damaged kidneys, this happens through dialysis.Credit: Ziad M. El-Zaatari/SPL

    The WHO secretariat, which works closely with the nephrology community, welcomes the call to include kidney disease as an NCD that causes premature deaths, says Slim Slama, who heads the NCD unit at the secretariat in Geneva, Switzerland. The data support including kidney disease as an NCD driver of premature death, he adds.

    The decision to include kidney disease along with other priority NCDs isn’t only down to the WHO, however. There must be conversations between the secretariat, WHO member states, the nephrology community, patient advocates and others. WHO member states need to instruct the agency to take the steps to make it happen, including providing appropriate funding for strategic and technical assistance.

    Data and funding gaps

    Three reports based on surveys by the International Society of Nephrology since 2016 highlight the scale of data gaps (A. K. Bello et al. Lancet Glob. Health 12, E382–E395; 2024). In many countries, screening for kidney disease is difficult to access and a large proportion of cases go undetected and therefore uncounted. For example, it is not known precisely how many people with kidney failure die each year because of lack of access to dialysis or transplantation: the numbers are somewhere between two million and seven million, according to the WHO. Advocates must push public-health officials in more countries to collect the data needed to monitor kidney disease and the impact of prevention and treatment efforts.

    Even with better data, treatments for kidney disease are often prohibitively expensive. They include dialysis, an intervention to filter the blood when kidneys cannot. Dialysis is often required two or three times weekly for the remainder of the recipient’s life, or until they can receive a transplant, and it is notoriously costly. In Thailand, for example, it accounted for 3% of the country’s total health-care expenditures in 2022, according to the country’s parliamentary budget office.

    End chronic kidney disease neglect

    These costs could come down if people who have diabetes or high blood pressure, for example, could be routinely screened for impaired kidney function, because they are at high risk of developing chronic kidney disease. This would enable kidney damage to be detected early, before symptoms set in, opening the way for treatments that do not immediately require dialysis or transplant surgery.

    New drugs that boost weight loss and treat type 2 diabetes could also help to prevent or reduce stress on the kidneys, but these, too, are too expensive for many people in need. That is why something needs to be done to make drugs more affordable. The pharmaceutical industry, which has become extremely profitable, has a crucial role. In Denmark, for example, the industry’s profits helped to tip the national economy from recession into growth in 2023, according to the public agency Statistics Denmark. The COVID-19 pandemic showed that making profits and making drugs available, and affordable, to a wide population need not be mutually exclusive. Similarly innovative thinking is now needed. “The whole world needs to reckon with this kidney problem,” says Valerie Luyckx, a biomedical ethicist at the University of Zurich in Switzerland.

    The WHO adding kidney disease to its priority list could also attract funding for treatment, research and disease registries. That could jump-start the development of new treatments and help to make current treatments more affordable and accessible.

    NCDs are responsible for 74% of deaths worldwide, but the world’s biggest donors to global health currently devote less than 2% of their budgets for international health assistance to NCD prevention and control, and not including kidney disease. Drawing more attention to the quiet rampage of kidney disease among some of the most vulnerable people would be one important step in turning these statistics around.

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  • Depleting myeloid-biased haematopoietic stem cells rejuvenates aged immunity

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  • Bird-flu threat disrupts Antarctic penguin studies

    Bird-flu threat disrupts Antarctic penguin studies

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    Brown Skua, Stercorarius antarcticus, calling in front of a King Penguin colony.

    Avian flu has been detected sub-Antarctic king penguins.Credit: Education Images/Universal Images Group via Getty

    A deadly strain of bird flu circulating worldwide is disrupting research in Antarctica and could lead to the cancellation of some projects to study penguins, seals and other animals next year.

    “This is the first time I remember such reduced access to animal colonies since I started my Antarctic career in 1996,” says microbiologist Antonio Quesada del Corral, who manages the Spanish Antarctic research programme and is based in Madrid.

    “Several projects were cancelled this year, because we wanted to reduce the risk of having an infection of people or being the vector that spreads sickness between different animal colonies,” he says. “We had scheduled for next year more new projects on animal colonies — some of these are now likely not going to take place.”

    Antarctic seals recruited to measure effects of climate change

    Researchers first detected avian influenza, caused by the circulating H5N1 subtype of the virus, in the wider Antarctic region in October 2023. They found the virus in dead birds, including skuas and gulls, in the sub-Antarctic territory of South Georgia and the South Sandwich Islands.

    This sparked fears among scientists that bird flu would soon reach Antarctica itself. “We were very afraid,” says Quesada del Corral. As a result, he says, the Spanish Antarctic research programme was revised for the summer season, which runs from around October to late March. Since then, only researchers specializing in infectious diseases and viruses have been allowed access to animal colonies, he adds. In the sub-Antarctic, the virus is known to have spread to elephant and fur seals, albatrosses, terns, gentoo penguins and king penguins, suggesting that these animals are also at risk in Antarctica.

    Data disruption

    Researchers involved in about half a dozen projects have been unable to collect data from sensors that are located in animal colonies and gather information year-round, says Quesada del Corral. “We had several projects that needed to download information from some sensors [located] in colonies of penguins, sea lions, elephant seals, leopard seals — and they were not able to go in there.”

    Some of these long-term projects aim to monitor animal behaviour — for example, to determine when penguins hatch, moult and move to or from a rookery. Others aim to track the impacts of the animals on the environment, or to sample bacteria in aerosols produced by the colonies.

    How to stop the bird flu outbreak becoming a pandemic

    In theory, data collected by sensors could still be retrievable next year. “The memory of the sensors is normally about two years,” says Quesada del Corral. “We usually change the battery every year. Hopefully next year they will have at least partial data collected.”

    But there is a chance that the batteries will fail, or that restrictions could tighten. “I really am afraid that next year the season is going to be worse than this,” he adds.

    The activities of Argentine researchers have also been disrupted by bird flu, says Martín Ansaldo, an ecologist at the Argentine Antarctic Institute in Buenos Aires. “We suspended all activities that had direct contact with animals, wherever we observed animals with unusual behaviour or an unusual increase in the number of dead,” he says. This affected scientists studying the reproduction, behaviour and physiology of birds and mammals.

    Research carried out under the US Antarctic Program has not yet been disrupted by bird flu, according to the National Science Foundation (NSF), which funds the programme. Nonetheless, “it is possible that any future outbreak detected could impact research”, an NSF spokesperson told Nature. “Decisions will be made on a case-by-case basis.”

    Tip of the iceberg

    Researchers’ fears were confirmed in February, when H5N1 was detected on the Antarctic mainland for the first time. The virus was found in dead skuas near Argentina’s Primavera research station, located on the Antarctic Peninsula, which stretches north towards South America. “With this confirmation, we know that the infection can reach any colony in a few days,” says Quesada del Corral.

    Scientists have just started a new expedition to sample for bird flu on the Antarctic Peninsula, says Antonio Alcamí, a virologist based at the Severo Ochoa Centre for Molecular Biology in Madrid, who was among those who first detected H5N1 on the mainland.

    Monitoring the spread of the virus will help to protect researchers on Antarctica. “The confirmation of H5N1 [on the mainland] generated an early warning to take extreme care of the people working in Antarctica, both logistical and scientific,” says Ansaldo. “We must be prepared to protect both the Antarctic fauna and the human beings working there.”

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  • Fungal diseases are spreading undetected

    Fungal diseases are spreading undetected

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    Two people wearing surgical gowns, face masks, and hair coverings, stand on either side of a patient (lying down in centre of image), performing surgery

    Surgeons operate to remove ‘black fungus’ from a person’s lung.Credit: Prakash Singh/AFP via Getty

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    In mid-2021, a deadly fungal disease called mucormycosis began surging in India’s crowded hospitals. Often referred to as ‘black fungus’, and caused by various common mould species, mucormycosis typically invades structures in the face and brain. But during the Indian outbreak, thousands of people in hospital — most of them undergoing steroid treatment for severe COVID-19 — developed fungal infections that festered unseen in the lungs1. “We missed a lot of pulmonary mucormycosis during COVID,” says microbiologist Arunaloke Chakrabarti, director of the Doodhadhari Burfani Hospital and Research Institute in Haridwar, India. The expertise and tests needed to diagnose the condition were frequently unavailable, Chakrabarti says, and many people died before they could be treated.

    Part of Nature Outlook: Neglected tropical diseases

    India’s experience with mucormycosis reflects a broader diagnostic predicament: many low- and middle-income countries (LMICs) lack even the most basic tools for detecting the fungal diseases that kill an estimated 2.5 million people each year2. Misdiagnosis often leads to incorrect treatment, and, because people who are immunocompromised are particularly at risk, expanding use of steroids and other immune-suppressing drugs is contributing to the growth of vulnerable populations. People with HIV, cancer and respiratory diseases are especially at risk, particularly where poor sanitation and over-crowding aids the spread of fungal pathogens3.

    As fungal disease rates rise steadily, efforts to shore up the ability of LMICs to diagnose the conditions have taken on a new urgency. In 2022, the World Health Organization (WHO) released its first-ever ranking of fungal health threats, with the aim of strengthening the global response to infections. The report emphasized that expanded access to diagnostics will help policymakers to better assess the burden of fungal diseases, so that resources and attention can be allocated more appropriately.

    A global problem

    Surveys of diagnostic capacity in LMICs over the past few years reveal a dire situation. Methods in many places are limited to conventional microscopy and fungal culture, both of which have shortcomings. Microscopy, for example, requires the expertise of people who can identify fungal pathogens by their appearance. Such specialists are typically unavailable in remote settings. And it can take up to one month to culture a sufficient quantity of fungal cells for microscopic analysis. That’s too long for people who are acutely ill, such as those “with fungal sepsis or fungal meningitis, who need a more immediate diagnosis”, says Marcio Louenco Rodrigues, a mycologist at the Oswaldo Cruz Foundation, a research institute in Curtiba, Brazil. Certain pathogens, including Pneumocystis jirovecii, which causes pneumonia, can’t be cultured at all.

    In the absence of a diagnosis, physicians will often treat suspected infections on the basis of symptoms. But that approach comes with risks. Some fungal pathogens, including Mucorales, Histoplasma and Aspergillus cause lethal pulmonary infections that can be easily confused with tuberculosis, which is a bacterial disease4. Fungal infections don’t respond to antibiotics. And by the time people who are initially misdiagnosed with tuberculosis receive antifungal therapy, “many are already dying”, says Claudia Banda, an infectious-disease specialist at Cayetano Heredia University in Lima, Peru.

    A key step towards boosting diagnostic capacity is to broaden access to simple, point-of-care assays that can be used cheaply in remote settings. “This is what developing countries really want,” says David Denning, a research clinician at the University of Manchester, UK. Denning was the founding president of the Global Action Fund for Fungal Infections (GAFFI), a non-governmental advocacy group headquartered in Geneva, Switzerland. GAFFI played a key part in selecting tests for fungal diseases for the WHO’s list of essential diagnostics, which was first released in 2018.

    Topping that list are lateral flow assays that generate fast diagnostic results and cost less than US$5 each. These sorts of assay will be familiar to many as home-test kits for COVID-19. They detect microbial antigens or immune antibodies in blood and other fluids and have already been standardized for several fungal pathogens. For example, the WHO recommends screening people with HIV who have critically low white blood cell counts for cryptococcal antigen, which would indicate the presence of a harmful fungal infection that can cause meningitis5.

    Lateral flow assays detect Cryptococcus with high accuracy. But in Africa — which is home to around 65% of people in the world with HIV — only around 25% of the population has access to the test, according to a survey funded by GAFFI3. And Latin American countries have similar shortages. In 2023, Banda and her colleagues surveyed Peru’s public hospitals, and found that only 13% of them could provide cryptococcal antigen testing (unpublished data).

    A push to expand access

    Uptake is thwarted by a lack of awareness of fungal infections, says Rodrigues, adding that for many fungal pathogens, there are no lateral flow tests. Cost is also a barrier, because although the price per test is low, rolling them out at scale would impose substantial burdens on already stretched health-care systems.

    Image on left: black and white brain image with orange area to the right of centre. Image on Right: green spherical fungus particles of varying sizes, on dark background

    A brain scan reveals cryptococcal meningitis, which can be caused by the fungus Cryptococcus neoformans (right).Credit: Cultura Creative RF/Alamy; Dennis Kunkel Microscopy/SPL

    Routine use of the assay could save many lives — Cryptococcus kills nearly 150,000 people a year2. However, Banda points out that the main drug therapy for cryptococcal meningitis, amphotericin B, is also exceedingly toxic, “so we like to have some definitive evidence of the disease before we start treatment”.

    Broadening diagnostics for other fungi that can cause serious illness, such as Aspergillus and Histoplasma, could also save lives. According to Denning, as many as 10% of people with suspected tuberculosis actually have chronic pulmonary aspergillosis. “So, all tuberculosis clinics around the world should be testing for it,” he says. Denning’s research on the global incidence of fungal diseases found that more than 2 million people each year develop invasive aspergillosis2, which occurs when the fungi spreads through the body. Histoplasmosis is also endemic in many LMICs, and if left untreated, mortality in people with HIV is 100%, Banda says.

    Banda’s fungal-disease work in Peru, which is funded by the US Centers for Disease Control and Prevention, shows that histoplasmosis is endemic among people with HIV, cancer and other immune-suppressing conditions who live in and around the country’s coastal jungles. Bat droppings in these areas are a ready source of the fungus spores. Accurate estimates of the number of people affected are unavailable, however, owing to the lack of access to diagnostic testing, Banda says. She cites a similar need for access for chronic pulmonary aspergillosis and Candida auris — a hospital scourge that’s notoriously difficult to eliminate or control. The fungus C. auris, in particular, is an emerging global-health threat; some strains resist all antifungals and incur death rates as high as 70%. In Peru, the pathogen emerged several years ago, “and not all our microbiology labs are adequately prepared for it”, Banda says.

    Advocates are calling for lateral flow assays to be developed for a broader array of fungal diseases. Along those lines, researchers at the University of Exeter, UK, are developing an assay specific to Rhizopus arrhizus6 — a fungal spore responsible for most human cases of mucormycosis, the disease that plagued India during the COVID-19 pandemic.

    But lateral flow assays can’t solve the diagnostic shortages on their own. The tests are valuable as screening indicators that reveal whether a given pathogen is — or was — present in the body, but they don’t measure the extent of a fungal infection, or “how well a patient responds to treatment”, says Amir Seyedmousavi, a clinical microbiologist at the National Institutes of Health Clinical Center, in Bethesda, Maryland. Patient monitoring requires more advanced analytical techniques, Seyedmousavi says, such as polymerase chain reaction (PCR) sequencing and other molecular tests. The laboratory capacity needed for these technologies, however, is often unavailable in resource-poor areas.

    Seyedmousavi chairs the Fungal Diagnostic Working Group of the International Society for Human and Animal Mycology. The group is working to standardize and improve affordable diagnostic tests — especially for LMICs. And it aims to create international networks for knowledge sharing and education. Chakrabarti, meanwhile, is working to establish diagnostic reference centres across India that offer a range of standardized diagnostics — not just at the hospitals at which they are based, but also at the clinics that serve as the first point of contact for health care. The reference centres provide training to boost laboratory workforces, Chakrabarti says, and staff there conduct epidemiology studies to map the distribution of fungal diseases throughout the country.

    Person seated in room below window, wearing a face mask. To the right, person standing wearing PPE looking at MRI

    During the peak of the COVID-19 pandemic, mucormycosis cases surged in India.Credit: Prakash Singh/AFP via Getty

    GAFFI is sponsoring similar approaches in other parts of the world. In partnership with the non-profit organization the Asociacion de Salud Integral in Guatemala City, for instance, GAFFI sponsored a diagnostic demonstration that focused on a number of fungal diseases, including histoplasmosis and cryptococcosis. In 2023, GAFFI reported that mortality from fungal infections in people with HIV could be substantially reduced with readily available diagnostics and treatment.

    Efforts to expand access to diagnostic tests face complex challenges. Because clinical awareness of fungal diseases is low in LMICs, physicians don’t request diagnostic tests often enough to create a market that could make the tests more readily available. In the absence of better information on prevalence — especially outside urban areas — health systems in low-income countries have failed to prioritize fungal diseases, Banda says, creating a vicious cycle of neglect.

    Health-care financing poses extra hurdles. In some LMICs, people have to pay for fungal diagnostic tests out of their own pocket. “People don’t want to pay for a test that might be negative,” Denning says. “They just want the doctor to make a judgement about treatment. For the life-threatening fungal diseases — the ones that cause meningitis or sepsis or pneumonia — that can be tough.”

    Denning argues that teaching hospitals in LMICs should have access to every test on the WHO’s list of essential fungal diagnostics, and that the tests should also be made freely available to people at the point of use. If hospitals don’t improve their capacity to detect and treat fungal diseases correctly, he warns, “then acquired microbial resistance and inappropriate use of all these antimicrobials just becomes rife”. Fortunately, diagnostic tests are steadily becoming cheaper, “so it should be possible to provide them at low-cost around the world,” Denning adds. “The big need is just to get them into everybody’s hands.”

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  • Dopamine receptor D2 confers colonization resistance via microbial metabolites

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  • Meningitis could be behind ‘mystery illness’ reports in Nigeria

    Meningitis could be behind ‘mystery illness’ reports in Nigeria

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    General view of a busy road at sunset.

    The Nigerian health ministry has been told to investigate reports of deaths in the northeastern state of Gombe (pictured).Credit: Tolu Owoeye/Shutterstock

    The World Health Organization has confirmed that reports of an ‘unknown’ disease allegedly responsible for 30 deaths in Gombe State, Nigeria, in mid-February can be linked to three cases of meningitis that are part of ongoing seasonal outbreaks.

    The agency tells Nature that it is aware of reports of dozens of fatalities, but that on investigation it has found there have in fact been just three, resulting from confirmed cases of meningitis.

    Nigeria’s Centre for Disease Control and Prevention and the regional Africa Centres for Disease Control and Prevention have not confirmed or denied an unknown-disease outbreak in Gombe State. Neither organization responded to requests for comment from Nature’s news team.

    The case highlights the importance of thorough disease-surveillance systems and the need for timely communication, say researchers. West African countries are on high alert for flare-ups of infectious diseases. Nigeria, the most populous African country and the one with the largest economy, is currently struggling with surges of Lassa fever, diphtheria and meningitis. In recent years, it has also contended with spikes in cholera, mpox (formerly called monkeypox) and Ebola, as well as COVID-19. High mobility between countries in the region makes residents particularly susceptible to the rapid spread of infections, according to a 2022 study published in The Lancet1.

    Unknown disease?

    On 27 February, Nigeria’s National Assembly instructed the country’s health ministry to investigate a “strange disease” said to have killed more than two dozen people in the northeastern state of Gombe.

    News of the deaths had come from an 18 February Facebook post regarding unexplained deaths at the Nafada General Hospital, said to have occurred within 24 hours of the victims contracting an unknown disease that caused abdominal pain, diarrhoea and fever.

    But on 28 February, Gombe State commissioner of health Habu Dahiru denied the report of mystery deaths, according to local newspapers. “Formally, we received cases with symptoms suggestive of cerebrospinal meningitis in the Nafada local government area on 18 February and immediately swung into action,” he told media outlet Punch.

    “The more specific and plainly described information is given about what is known and not known promotes confidence that the authorities are sincerely trying to give the best quality information,” says Julii Brainard, who models public-health threats at the University of East Anglia in Norwich, UK.

    “The void created by limiting or not giving the necessary fact-checked information can be filled by mis- or disinformation or rumors,” says Sílvia Majó Vázquez, a political-communication researcher at Arije University Amsterdam in the Netherlands. It can be difficult to correct the false information once it is circulating, she adds.

    Surveillance systems

    Public-health bodies in the region are attuned to potential outbreaks, says Robert Garry, a virologist at Tulane University in New Orleans, Louisiana, who works with scientists in Sierra Leone and Nigeria.

    “People are aware that viruses are of serious concern and need to be dealt with aggressively”, especially after the COVID-19 pandemic, he says. The 2014 Ebola outbreak was also a “wake-up call” to West African countries, Garry adds. Between 2013 and 2016, more than 11,000 people in Guinea, Liberia and Sierra Leone died of this viral haemorrhagic fever. Eight people in Nigeria died of the disease.

    In the years since, “the Nigerian CDC put their best foot forward”, says Garry. “They’ve got a lot of good people there. They’re putting the appropriate resources into it.”

    Virologist Peter Piot, former director of the London School of Hygiene & Tropical Medicine, agrees that there have been major efforts to improve disease surveillance in West African countries over the past decade. “The Nigerian Centres for Disease Control have done excellent work on Lassa and monkeypox,” he says. But he adds that in such a large country, surveillance can be “uneven”, and the system is constantly being tested. Last week, Yobe State — north of Gombe — quarantined more than 200 people after reports of 20 meningitis-related deaths in the province, Punch reported.

    Trust between health authorities and citizens is vital, says Brainard. If people feel that authorities are hiding information or are clueless, “then people try to figure out their own explanations, which may be completely wrong”, she says.

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  • why a vaccine campaign is unlikley to stop it

    why a vaccine campaign is unlikley to stop it

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    Rio de Janeiro's Health Secretary Daniel Soranz applies a dose of the Qdenga dengue vaccine to a young recipient.

    A dose of the Qdenga vaccine against dengue is given to a young recipient in Brazil.Credit: Buda Mendes/Getty

    An explosive rise in dengue cases in Brazil has health authorities on edge. In the first two months of 2024, the country registered more than one million cases of the mosquito-borne disease. That’s a record for this period — and Brazil’s dengue cases normally peak between March and May (see ‘Dengue’s early surge in Brazil’).

    Factors such as climate change and rapid urban growth are fuelling the surge, which has already killed at least 214 people this year. In response to the crisis, Brazil has become the first country to roll out a public vaccination campaign against dengue.

    The campaign is an important addition to the fight against dengue, scientists say. But they warn that the effort is too modest to solve the immediate crisis. “Very few people are being vaccinated. To have an impact on the rates, we would need to have mass vaccination,” says Ana Lúcia de Oliveira, an infectious-disease specialist at the Federal University of Mato Grosso do Sul in Campo Grande, Brazil. And even widespread vaccination won’t defeat the disease unless basic sanitation problems are addressed, researchers note.

    A disease on the rise

    Dengue is a viral disease transmitted by the Aedes aegypti mosquito, which thrives in hot and humid conditions, laying its eggs in stagnant water found in everything from discarded tyres to flower vases. There is no specific treatment for the disease, which can cause fever and body aches and, in severe cases, internal bleeding and death.

    DENGUE’S EARLY SURGE IN BRAZIL. Graphic compares dengue cases in Brazil for 2023 and 2024.

    Source: Ministry of Health of Brazil

    Rising temperatures associated with climate change have contributed to an expansion of the disease into the southernmost region of Brazil, which was once too cold for A. aegypti. An El Niño event that arrived in mid-2023 and is predicted to last until at least April is intensifying the heat and rainfall, further contributing to the surge, says Bárbara Valente, an epidemiologist at the Oswaldo Cruz Foundation in Rio de Janeiro, Brazil.

    Mosquito paradise

    But climate is not the only factor to blame for the surge. “The cities are growing and becoming paradise for mosquitoes,” says Marcia Castro, a public-health specialist at Harvard T.H. Chan School of Public Health in Boston, Massachusetts. Adequate sanitation infrastructure often fails to keep pace with the growth of Brazilian cities. Uncollected rubbish becomes a breeding ground for the insects, as does water stored by people who don’t have regular access to tap water.

    How genetically modified mosquitoes could eradicate malaria

    Furthermore, A. aegypti mosquitoes seem to be adapting to adverse conditions, says Joziana Barçante, a parasitologist at the Federal University of Lavras, Brazil. “We have been observing the presence of [A. aegypti] larvae where we previously did not find them,” she says. It is commonly understood that the mosquito prefers to breed in clean water, but studies show that it is now able to reproduce even in puddles and sewers1.

    Limited natural immunity is also contributing to the surge. Dengue is caused by four distinct viral subtypes — DENV-1, DENV-2, DENV-3 and DENV-4. After several years during which the first two predominated in Brazil, the last two have recently returned. Many Brazilians are vulnerable to these subtypes, and so more likely to become infected.

    Vaccine hopes

    Brazil’s public-health system is administering a vaccine called Qdenga, made by Takeda in Osaka, Japan, that has an overall efficacy of 73% against symptomatic dengue. Results were more promising against DENV-1 and DENV-2 than for DENV-3. For DENV-4, the efficacy data are inconclusive.

    Public distribution of the vaccine is currently limited to 521 cities, less than 10% of Brazil’s municipalities. The first stage of the campaign targets 10- and 11-year-olds, though health officials plan to expand it to children up to 14 years of age. That’s the age group most likely to be hospitalised other than elderly people, for whom the vaccine is not approved. The limited campaign “will only protect those few people who have been vaccinated”, says Oliveira.

    Modified mosquitoes reduce cases of dengue fever

    Vaccine availability is a big challenge: Brazil’s Ministry of Health says it has acquired all of the doses made available by Takeda and that the quantity is limited by the manufacturer’s capacity. Another challenge is that complete immunization requires two doses, with a three-month interval between them, which might complicate vaccine adherence.

    “The vaccine is not going to resolve the problem now,” says Castro. But she is hopeful about another vaccine, which hasn’t yet been approved, that is being developed by the Butantan Institute in São Paulo, Brazil. In a large clinical trial, it demonstrated an overall efficacy of 80% against symptomatic dengue with a single dose. But its effectiveness against DENV-3 and DENV-4 is unclear, because those subtypes did not circulate widely during the study period.

    Virus-fighting bacteria

    Among other technologies being explored to prevent dengue are modified mosquitoes carrying the Wolbachia bacterium, which reduces the insect’s capacity to transmit some viruses. Mosquitoes infected with Wolbachia have been released in several cities in Brazil, resulting in a local decrease in dengue cases.

    First genetically modified mosquitoes released in the United States

    Last year, a non-profit organization called the World Mosquito Program announced plans to build a massive mosquito factory, in partnership with the Oswaldo Cruz Foundation, to release modified mosquitoes in many of Brazil’s urban areas over the next ten years. Construction is yet to start, but the plan is to start production by the end of this year.

    For Valente, solving basic sanitation problems continues to be the essential step to overcoming dengue, with vaccines and other technologies as important auxiliary tools. “When you offer proper housing conditions, which includes access to clean water and proper waste collection,” she says, “you reduce the burden of many neglected diseases that could have even been eliminated in Brazil.”

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  • Why a cheap, effective treatment for diarrhoea is underused

    Why a cheap, effective treatment for diarrhoea is underused

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    Close-up of a Bangladeshi mother holding her warmly wrapped baby

    A salty-sweet solution is a cheap and effective way to prevent children’s death from diarrheal diseases. Yet doctors did not always recommend them.Credit: Jewel Samad/AFP/Getty

    “The gap between knowing the right thing and doing the right thing is a persistent problem,” says David Levine, a health economist at the University of California, Berkeley. That gap is highlighted by a study published today in Science1.

    Every year, half a million children under five die of diarrhoea globally — but doctors and pharmacists often don’t prescribe a cheap lifesaving treatment for the condition. A large Indian study suggests that this happens because prescribers don’t think that their patients want the therapy.

    Most private doctors and pharmacists in the study understand the benefits of an oral rehydration solution (ORS). The treatment, a pre-mixed sachet of salts and sugars that is mixed with water, has been around for more than half a century. It prevents dehydration and drastically reduces the risk of children dying from diarrhoea.

    To better understand why more children aren’t given ORS, Zachary Wagner, a health economist at the RAND Corporation, a non-profit research and policy organization in Santa Monica, California, and his colleagues launched a large experimental intervention in two Indian states, Karnataka and Bihar.

    They sent actors pretending to be the fathers of a sick two-year-old child to more than 2,000 randomly selected private doctors and pharmacists in mid-sized towns. Three-quarters of carers in India seek help for their sick children from private clinics and pharmacies.

    The interactions were designed to assess whether low levels of ORS prescription were due to supply shortages, incentives to sell more expensive drugs, such as antibiotics, or sensitivity to patient desires.

    Each actor arrived at a facility unannounced and explained that their child had been experiencing diarrhoea for two days. Some told the provider that they had previously used ORS to treat their child and asked whether they should use it again. Some instead mentioned antibiotics, and others brought up no earlier treatments. Some actors noted that they would not be purchasing any medications at the facility and just wanted advice. The researchers also sent a six-week supply of ORS to half of the facilities.

    The researchers found that a patient’s treatment preference was much more important than the clinic or pharmacy’s financial incentives and accessible stock in explaining why ORS is under-prescribed.

    Actors who expressed a preference for ORS were twice as likely to get it as those who mentioned no treatment. A survey of more than 1,000 carers across the two states and representatives from the clinics and pharmacies revealed that 48% of carers feel that ORS is the best treatment for diarrhoea, but only 16% express that preference when visiting clinics. In turn, only 18% of doctors and pharmacists think that their patients want ORS.

    “It is a very elegant study,” says Levine.

    Happy clients

    The results “somewhat go against the belief among economists that financial incentives matter an awful lot”, says Karen Grépin, a health economist at the University of Hong Kong. Instead, informational barriers were more important.

    But Ramanan Laxminarayan, an epidemiologist at Princeton University in New Jersey, says that financial incentives can be hard to disentangle from other motives. “We think of doctors as neutral decision-makers based on what is best for the patient, and that is often not the case,” says Laxminarayan. “Doctors make decisions based on what makes a patient happy,” he says, which has an underlying financial motive. “If a patient is not happy with you, they are not going to keep coming back.”

    Overall, Grépin says the study is impressive, but there is still a lot more to unpack. For example, it is not clear why some patients don’t communicate their preference for ORS to their providers. The study also doesn’t offer a clear path forward on how to improve ORS uptake, she says. “It doesn’t really tell me what to do next.”

    Wagner plans to design studies to test interventions for changing the perception of doctors and pharmacists, and how patients express their preferences. “Just telling people that ORS is a lifesaving medicine — we’ve hit the ceiling on what that can do.”

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