In 25 years of Kenyan data, RSV infant deaths in hospital have not fallen

Deaths among infants hospitalised with respiratory syncytial virus (RSV) pneumonia in coastal Kenya have not declined in 25 years, according to a quarter-century of surveillance at Kilifi County Hospital [s1]. The study's more useful finding is why some of those infants die and others do not: the strongest markers of death were severe undernutrition and congenital heart disease, not features of the virus itself [s1].

RSV is the leading cause of hospital admission for lower respiratory infection in infants worldwide, and more than 95% of the deaths it causes occur in low-income and middle-income countries [s1]. Yet the predictors of who dies after being admitted with RSV have been poorly defined — which is what this cohort set out to fix.

The data

Researchers analysed 25 successive RSV seasons of paediatric surveillance at Kilifi County Hospital in Kenya [s1]. Of 75,482 infant admissions between 1 January 2001 and 13 July 2025, 19,299 (25·6%) met WHO pneumonia criteria and 2,745 (22·7%) of those tested positive for RSV [s1]. The analysis focused on the 2,390 post-neonatal infants — those aged 28 days to 12 months — who made up 87·1% of the RSV group [s1].

Of those infants, 58 (2·4%) died in hospital, and 44 (76%) of those deaths occurred within seven days of admission [s1]. Across the full 25-year span there was no evidence of a sustained decline in RSV-associated in-hospital mortality, nor of any improvement in the infants' nutritional status [s1]. The study was funded by the Bill & Melinda Gates Foundation and Wellcome [s1].

What predicted death

Three factors were independently associated with dying in hospital. Congenital heart disease carried an odds ratio of 3·51 (95% CI 1·37–8·97) [s1]. Severe undernutrition raised the odds by 1·59 (1·28–1·99) for each one-unit reduction in weight-for-age Z score — a continuous measure, so the risk climbs the more underweight an infant is [s1]. Hypoxaemia contributed an odds ratio of 1·05 (1·03–1·08) for each one-percentage-point fall in peripheral oxygen saturation [s1].

The malnutrition signal was stark in absolute terms as well. Of 54 infants with RSV who died in hospital and had the measurement, 38 (70·4%) had a mid-upper arm circumference below 11·5 cm — the threshold for severe acute malnutrition [s1]. In other words, most of the infants who died were already severely wasted when they arrived.

Why a static death rate matters

The absence of improvement over 25 years is itself the story. Kilifi is a long-running, well-resourced surveillance site; if in-hospital RSV mortality were going to fall through better supportive care alone, this is where it would show. That it has not suggests the deaths are being driven by conditions present before the child reaches hospital — chronic undernutrition and underlying heart disease — that admission-day treatment cannot reverse [s1].

That reframes what would reduce these deaths. The authors argue their findings support targeted nutritional interventions, because the anthropometric deficits that mark the highest-risk infants are established long before an RSV season begins [s1]. A ventilator and oxygen treat the episode; they do not undo months of wasting.

The other lever is prevention of the infection itself, and it is closer than it has been. In September 2026 WHO prequalified a multi-dose RSV vaccine vial, a step it framed as widening access to protect more infants globally [s2]. Maternal RSV immunisation and long-acting antibodies are designed to keep infants out of hospital in the first place — which, on this study's evidence, is where the avoidable mortality is decided, since supportive care after admission has not moved the death rate in a generation.

The limits

This is a single-site cohort, and its strength — 25 uninterrupted years at one hospital — is also its boundary: Kilifi's population, referral patterns and case mix are its own, and the mortality figures are for infants sick enough to be admitted, not for all infants who catch RSV [s1]. The predictors, though, are the kind that travel. Severe undernutrition and congenital heart disease raise the stakes of a common infection in any setting where children arrive at hospital already compromised.

This article is informational and is not medical advice.

Sources

• [s1] "In-hospital and post-discharge mortality among infants with respiratory syncytial virus in rural Kenya: a 25-year retrospective cohort study," The Lancet Global Health, 10 July 2026. https://doi.org/10.1016/j.langlo.2026.104003
• [s2] "WHO prequalifies multi-dose RSV vaccine vial, paving the way to protecting more infants globally," World Health Organization, 9 September 2026. https://www.who.int/news/item/09-09-2026-who-prequalifies-multi-dose-rsv-vaccine-vial--paving-the-way-to-protecting-more-infants-globally