The study’s central conclusion is stark: the majority of hospitalisations and deaths among children in their first two years of life are caused by infectious diseases that are, in principle, preventable. Malaria alone accounted for 54.3 percent of all hospital admissions recorded during the follow-up period, dwarfing every other cause of severe illness. Lower respiratory infections ranked second at 16.7 percent of admissions, followed by diarrhoeal disease at 9.6 percent, undernutrition at 7.4 percent and sepsis at 4.8 percent. Among deaths that occurred in hospitals with available medical records, malaria was responsible for 50.6 percent, meaning that one in every two in-hospital deaths in this age group was attributable to a single parasitic disease transmitted by mosquitoes.

The burden extends beyond hospital walls. For children who died outside medical facilities, the research team reconstructed probable causes of death through standardised interviews with family members and caregivers, a well-established epidemiological technique known as verbal autopsy. This analysis likewise identified malaria as the most frequent cause of death, followed by respiratory infections and diarrhoea. The researchers caution, however, that verbal autopsy is likely to underestimate malaria mortality, because the fever and generalised symptoms characteristic of severe malaria overlap considerably with those of other common infectious diseases, making it difficult for bereaved caregivers to distinguish between them when recalling a child’s final illness.

The scale and precision of the study distinguish it from previous efforts to characterise early childhood disease burden in the region. Routine surveillance systems in Sierra Leone and many other countries typically group all children under five into a single reporting category, a practice that obscures the distinct epidemiology of infancy and early toddlerhood and makes it difficult to identify precisely which conditions drive hospitalisation and death at different ages. To close this gap, the ICARIA team combined continuous health facility surveillance with household visits, telephone follow-up and a network of community informants, creating an unusually complete record of both severe illness and mortality across the first two years of life.

“To address this important knowledge gap, we followed 20,560 infants up to 24 months of age across 14 health centres in three districts of Sierra Leone,” explained Kwabena Owusu-Kyei, an ISGlobal researcher based in Sierra Leone and first author of the study. “By combining health facility surveillance with household visits, telephone follow-up and community informants, we were able to build a much more complete picture of childhood hospitalisations and deaths.” During the follow-up period, the cohort recorded 2,688 hospital admissions and 859 deaths, figures that translate into an extraordinary concentration of severe disease in a population of children who had, by the study’s design, access to facilities offering free healthcare.

The context of Sierra Leone’s public health landscape makes the findings all the more consequential. Over the past decade and a half, the country has introduced a series of major initiatives aimed at reducing child deaths, including a policy of free healthcare for children under five, malaria chemoprevention programmes, pneumococcal vaccination and, more recently, the rollout of the malaria vaccine. Yet until now, it has been difficult to assess how these interventions are affecting survival during the first two years of life, the period when children are most vulnerable to the infectious diseases that dominate the region’s disease burden. The new study provides the granular evidence base that such assessments require.

Beyond quantifying the burden of disease, the study identified several factors strongly associated with a child’s chances of survival, offering concrete targets for intervention. Children who had received all the routine vaccines of the Expanded Programme on Immunization (EPI) due for their age had a 35 percent lower risk of overall mortality compared with incompletely vaccinated children. Complete vaccination was also associated with a 29 percent lower likelihood of dying during a hospital admission and, strikingly, a 44 percent lower risk of death in the period after discharge from hospital, a finding that underscores how vaccination status shapes resilience well beyond the immediate protection conferred against specific vaccine-preventable pathogens.

Malaria chemoprevention also emerged as a powerful protective factor. Children who received all scheduled doses of sulfadoxine–pyrimethamine, the preventive antimalarial treatment delivered through Sierra Leone’s immunisation programme, had a 40 percent reduction in mortality risk compared with those who missed doses. Conversely, undernutrition significantly increased the risk of dying during hospitalisation, a result that reinforces long-standing calls to integrate nutritional support into paediatric care rather than treating malnutrition and infectious disease as separate clinical problems. Taken together, these associations suggest that the tools needed to save young lives largely already exist within the health system, but that coverage, adherence and integration remain insufficient.

The study arrives at a moment of broader concern for global child health. Worldwide, child mortality has declined substantially over recent decades, one of the great public health achievements of the modern era, but the progress achieved up to 2015 has since stalled. In many countries across sub-Saharan Africa, infectious diseases remain among the greatest threats to survival during the first years of life, and the stagnation of mortality declines suggests that existing strategies are not reaching their full potential. Sierra Leone, still rebuilding its health system after decades of civil war and the 2014 Ebola epidemic, exemplifies the challenge facing the world’s most vulnerable settings.

“These findings show that there is still a substantial unfinished agenda in global health, and that strengthening vaccination, malaria prevention, community-based care and post-discharge follow-up are essential to reducing child mortality in the world’s most vulnerable settings and meeting the Sustainable Development Goals,” concluded Clara Menéndez, Director of ISGlobal’s Maternal, Child and Reproductive Health Programme and principal investigator of the study. With the Sustainable Development Goal target of ending preventable deaths of newborns and children under five by 2030 drawing closer, the Sierra Leone cohort offers both a warning and a roadmap: the diseases killing the youngest children are known, the preventive tools are available, and the decisive variable is whether they reach every child who needs them.

Subject of Research: Causes of hospitalisation and death from malaria and other infectious diseases in children under two in Sierra Leone

Article Title: Malaria remains the leading cause of hospital admission and in-hospital death in children under two in Sierra Leone

Article References: Malaria remains the leading cause of hospital admission and in-hospital death in children under two in Sierra Leone. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: malaria, child mortality, Sierra Leone, The Lancet Global Health, ISGlobal, ICARIA project, vaccination, chemoprevention, sulfadoxine-pyrimethamine, undernutrition, respiratory infections, verbal autopsy

The analytical foundation of the report is the Global MPI, an index built from ten indicators spanning three dimensions: health, education, and living standards. A household is classified as multidimensionally poor if it is deprived in at least a third of these ten indicators. What distinguishes the new study is its pairing of this household-level measure with individual-level data on children themselves, specifically their nutritional status and school attendance. This is the first global multidimensional study of children’s experiences of poverty within the home based on observed household survey data, covering 97 countries for undernutrition and 108 countries for school attendance. By linking individual and household deprivations, the researchers can quantify not just how many children are deprived, but how many deprivations each child carries simultaneously.

The headline numbers are stark. Across the 97 countries with available nutrition data, covering 518 million children under five, roughly one-third are undernourished, meaning they are either stunted or underweight. Globally, 96 million undernourished children also live in multidimensional poverty, equivalent to one in five children in the surveyed population. Perhaps most striking is the intensity of deprivation among this doubly disadvantaged group: each multidimensionally poor and undernourished child experiences, on average, four to five additional deprivations beyond undernutrition itself, whether in access to clean cooking fuel, safe drinking water, sanitation, electricity, schooling, or housing. Deprivation, the data suggest, rarely travels alone.

The schooling picture follows a similar pattern. Across 108 countries with available data, 13 percent of the 1.04 billion school-aged children are out of school, a total of 136 million children. More than 80 percent of all out-of-school children are also multidimensionally poor, numbering 110 million. Each poor out-of-school child experiences an average of five additional deprivations across the other nine Global MPI indicators. Taken together, 31 percent of the 1.04 billion school-aged children covered by the study are out of school, multidimensionally poor, or both. Sabina Alkire, Director of OPHI and co-author of the study, said she was shocked by how tightly clustered the intensity of poverty is for children, noting that the data reaffirm the need for multisectoral approaches to development programmes such as social protection.

One of the report’s most methodologically significant findings concerns inequality within households. Rather than assuming that all children in a poor household share the same disadvantages, the researchers examined whether deprivation is distributed evenly among siblings. It is not. Over one-third of poor children under five live in a household in which at least one child is undernourished while another is not. Similarly, over one-third of poor children live in households where some school-aged children attend school and others do not. This intra-household variation, documented at global scale for the first time, carries a pointed implication for programme design: interventions that treat the household as a uniform unit of disadvantage may miss children whose needs are invisible in aggregate statistics.

The report also paints a stark picture of women’s educational disadvantage and its relationship to child outcomes. In multidimensionally poor homes, over two-thirds of poor children, whether well-nourished or undernourished, live in a household where no woman has completed six years of schooling. By comparison, just over half live in households where no man has reached the same level of education. The gap widens further among poor children who are out of school: around 82 percent of poor out-of-school children live in households where no woman has completed six years of schooling, compared with 62 percent for households without a man who has reached that threshold. The association between maternal education and child outcomes has long been established in development research, but these figures quantify its scale across the developing world with unusual precision.

Gender disparities in school attendance vary considerably across countries, even though globally more girls than boys are out of school and more boys than girls are undernourished. In 19 countries, which together account for 56 percent of all out-of-school children, girls face higher rates of school exclusion than boys. The largest gaps appear in Afghanistan, where 67 percent of girls are out of school compared with 47 percent of boys, a difference of 20 percentage points. Pakistan follows, with 30.2 percent of girls out of school against 22.3 percent of boys, then the Central African Republic at 29.3 percent versus 21.5 percent, and Guinea at 41.3 percent versus 33.7 percent. These national-level contrasts illustrate how the same global phenomenon can be driven by very different local dynamics.

Amid the deprivation data, the report identifies a genuinely hopeful trend: pioneer children, defined as children aged 10 to 17 who are the only members of their household to have completed six years of schooling. Across the 108 countries studied, 71 million children fit this description. Half of them, 35 million, live in South Asia, where one in nine children aged 10 to 17 is a pioneer. By country, 28 million pioneer children live in India, over 3 million in Bangladesh, 2 million in Pakistan, 837,000 in Nepal, and 508,500 in Afghanistan. Notably, India, Bhutan, and Bangladesh all have higher shares of pioneer girls among girls aged 10 to 17 than pioneer boys among boys of the same age. Only in Afghanistan are pioneer boys more prevalent, at 7 percent of boys versus 4 percent of girls, and half of Afghanistan’s pioneer children are also multidimensionally poor.

The pioneer phenomenon is not without its complications. Globally, 9 percent of pioneer children live in homes where at least one other school-aged child remains out of school, a reminder that even households producing a first-generation learner can still contain children excluded from education. The researchers argue that supporting these young people, who are already breaking intergenerational cycles of low schooling, could mobilise significant change, particularly if programmes recognise the uneven distribution of educational opportunity within the very households that produce pioneers.

Alkire framed the report as a demonstration of what existing data can achieve when individual and household measurements are combined. This is the first study, she said, that shows at scale the possibility and importance of using existing individual data alongside household data to inform evidence-based programmes that meaningfully address cycles of poverty seeded by undernourished and out-of-school children. Invoking the economist Amartya Sen’s insight that nutrition and schooling carry both instrumental and intrinsic value, she called for collaborative work at the local level in measurement and policy to address the systemic deprivations that threaten to trap generations of children in poverty. For policymakers, the report’s central message is that child poverty is not a single problem but a dense web of overlapping deprivations, and that dismantling it requires interventions designed for the way disadvantage actually accumulates within homes.

Subject of Research: Multidimensional child poverty and undernutrition in developing countries

Article Title: 252 million young children in developing countries are undernourished, multidimensionally poor, or both, new global study finds

Article References: 252 million young children in developing countries are undernourished, multidimensionally poor, or both, new global study finds. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: child poverty, multidimensional poverty, undernutrition, Global MPI, school attendance, Oxford Poverty and Human Development Initiative, intra-household inequality, girls' education, South Asia, social protection, stunting, pioneer children

The investigation began with a deceptively simple behavioral question: given a choice, do mosquitoes prefer well-fed or undernourished hosts? Using controlled dietary restriction in laboratory mice, the researchers ran paired preference assays with multiple medically important mosquito species and found a consistent and striking result. Female mosquitoes preferentially oriented toward and fed on the undernourished animals. Because host-seeking in mosquitoes is governed by a layered integration of sensory cues, including carbon dioxide, heat, humidity, vision, and above all odor, the team reasoned that nutritional status might be altering the volatile chemical signature that hosts emit into the air. Behavioral experiments in which cues were selectively masked or manipulated confirmed that the differential attraction was olfactory in nature, pointing the investigators toward the skin surface as the source of the signal.

Gas chromatography-mass spectrometry analysis of volatile emissions from the skin of undernourished mice revealed a specific chemical culprit: elevated levels of volatile aldehydes. When these aldehydes were presented to mosquitoes in isolation or applied to otherwise unattractive hosts, they acted as potent attractants, reproducing the preference pattern observed with live undernourished animals. The aldehydes were not produced by the hosts themselves. Instead, they emerged from an unexpected intermediate player, the community of commensal bacteria that colonizes the skin. Sequencing and culture-based analyses showed that undernutrition was associated with a marked dysbiosis of the skin microbiota, with certain bacterial taxa proliferating to excessive densities and shifting their metabolic output toward aldehyde production. In effect, the mosquito-attractive odor was a microbial byproduct, released in greater quantities whenever the host’s nutritional state deteriorated.

The next question was mechanistic: why would a poor diet destabilize the skin microbiome in the first place? The answer lay in the dermal sebaceous glands, the microscopic structures that secrete sebum, a lipid-rich film coating the outer skin. The researchers found that undernutrition impaired the secretion of free fatty acids from these glands. Free fatty acids are not merely structural components of the skin barrier; they possess well-documented antimicrobial activity, suppressing the overgrowth of bacteria on the surface. With fatty acid output diminished, this chemical shield weakened, and commensal skin bacteria expanded unchecked. The team demonstrated this causal chain experimentally: restoring antimicrobial fatty acids, or reducing bacterial loads with antibiotics, both reversed the microbiota expansion and abolished the excess aldehyde emissions, thereby eliminating the heightened attractiveness of undernourished mice to mosquitoes.

To rule out confounding factors such as fur and general husbandry, the researchers extended their experiments to SKH1 hairless mice, in which skin surface chemistry can be sampled directly. The same pattern held. Undernutrition drove sebaceous dysfunction, skin bacterial overgrowth, dysbiosis, elevated aldehyde production, and increased mosquito attraction, providing a clean replication of the mechanism in a model system where the skin itself is fully accessible to analysis. The authors also showed that the effect operates in both directions of the transmission cycle. Undernourished mice were not only more likely to be bitten; they were also more susceptible to infection with dengue virus (DENV), developing higher viral loads. When mosquitoes fed on these viremic, undernourished hosts, the insects acquired virus more efficiently, and when infected mosquitoes subsequently fed, transmission onward was enhanced.

This dual effect, increasing both the probability that a host infects a mosquito and the probability that an infected mosquito infects a host, is what gives the finding its epidemiological weight. Vector-borne pathogens depend on a chain of events, each of which carries a probability, and interventions that raise or lower any single link can have outsized effects on the reproduction of an epidemic. By strengthening two links at once, host attractiveness and host infectivity, undernutrition may function as a critical modulator of transmission efficacy at the population level. The researchers present a model in which the prevalence of undernourished individuals within a community critically shapes the intensity of arbovirus circulation, a proposition with obvious implications for the geography of disease burden.

The human relevance of the mechanism was tested directly. In a cohort of undernourished human subjects, the team documented skin microbiota alterations mirroring those seen in mice, alongside elevated emission of volatile aldehydes from the skin. In behavioral assays, undernourished participants were more attractive to mosquitoes than their well-nourished counterparts. These converging lines of evidence, spanning rodent models, chemical analytics, microbiology, and human physiology, elevate the study beyond a correlation and support a coherent biological narrative: caloric and nutritional insufficiency suppresses sebaceous antimicrobial output, permits bacterial overgrowth, changes the skin’s volatile signature, and rewires the chemical conversation between humans and mosquitoes.

The broader context is sobering. Undernutrition and mosquito-borne disease overlap extensively across the tropics and subtropics, where food insecurity, poverty, and endemic dengue, malaria, Zika, and other arboviruses co-occur. Earlier work from the same field had established that host nutritional status can influence arbovirus virulence and evolution, and that host serum iron modulates dengue virus acquisition by mosquitoes, indicating that diet intersects with vector-borne transmission at multiple physiological levels. The new study adds skin chemistry and microbiota to this list and identifies a targetable axis. If aldehyde emissions and bacterial overgrowth mediate the effect, then interventions that restore sebaceous antimicrobial lipids, modulate the skin microbiome, or neutralize aldehyde cues could, in principle, reduce the excess bite risk borne by malnourished individuals, complementing bed nets, repellents, and vaccines.

For public health planners, the message is that nutritional support programs may double as disease control programs. Addressing undernutrition in regions where mosquito-borne pathogens are endemic would not only alleviate the direct morbidity and mortality of deficiency itself, but could also dampen the transmission cycles that keep those pathogens circulating. The authors argue that undernutrition should be recognized as a key driver of mosquito-borne disease transmission in nature, a reframing that places nutrition squarely within the toolkit of vector-borne disease control. As climate change expands the range of Aedes and Anopheles vectors and as food insecurity persists or worsens in many endemic regions, understanding and disrupting the metabolic link between diet, skin microbiota, and mosquito behavior may prove essential to bending the curves of some of the world’s most persistent epidemics.

Subject of Research: How undernutrition increases host attractiveness to mosquitoes and promotes the transmission of mosquito-borne diseases through skin microbiota changes.

Article Title: Undernutrition enhances host attractiveness to mosquitoes and transmission of mosquito-borne diseases

Article References: Wang, M., Song, X., Zhu, Y., Niu, J., Wang, G., Wang, Y., Xiao, H., Lei, D., Wu, T., Liu, L., Wang, P., Wang, J., & Cheng, G. (2026). Undernutrition enhances host attractiveness to mosquitoes and transmission of mosquito-borne diseases. Cell Research. https://doi.org/10.1038/s41422-026-01291-z

Image Credits: AI Generated

DOI: 10.1038/s41422-026-01291-z

Keywords: undernutrition, mosquito-borne diseases, dengue virus, skin microbiota, volatile aldehydes, sebaceous glands, fatty acids, host-seeking behavior, arboviruses, vector biology, malnutrition, disease transmission