Fiocruz's Landmark Nature Study on Chikungunya Exposure in Pregnancy

A groundbreaking study led by researchers from the Fiocruz Bahia's Centre for Data and Knowledge Integration for Health (CIDACS/Fiocruz Bahia) has uncovered significant long-term health risks for children exposed to chikungunya virus (CHIKV) during their mother's pregnancy. Published in the prestigious journal Nature Communications on March 21, 2026, the research reveals that such in-utero exposure increases the risk of hospitalization by 21% in the first three years of life compared to unexposed children. This finding underscores the hidden dangers of arboviral infections, even when no immediate symptoms appear at birth.

The study, titled "In-utero exposure to chikungunya and child morbimortality: a population-based study using linked routine data," draws from Brazil's extensive health registries, highlighting the power of big data in epidemiological research. Lead author Mio Kushibuchi and colleagues from Fiocruz, the London School of Hygiene & Tropical Medicine (LSHTM), and the Federal University of Bahia (UFBA) analyzed data on over 20,000 infants, providing robust evidence that challenges previous assumptions about chikungunya's impact on fetal development.

Chikungunya in Brazil: From Epidemic Waves to Endemic Threat

Chikungunya, caused by the chikungunya virus transmitted primarily by Aedes aegypti and Aedes albopictus mosquitoes, first arrived in Brazil in 2014. Since then, the country has reported nearly all global cases, accounting for 95% of worldwide notifications. In 2025 alone, Brazil saw hundreds of thousands of cases, with outbreaks intensifying due to urbanization, poor sanitation in vulnerable communities, and climate-driven mosquito proliferation.

Pregnant women are particularly at risk in endemic areas like Bahia, where socioeconomic inequalities exacerbate transmission. Vertical transmission—passing the virus from mother to child—occurs intrauterinely or perinatally, but long-term effects on offspring have been understudied compared to Zika virus. Fiocruz's work fills this gap, building on prior research showing chikungunya's association with neonatal morbidity and neurodevelopmental delays.

Innovative Methodology: Harnessing Brazil's Linked Health Data

Leveraging the Coorte de 100 Milhões de Brasileiros—a massive linked dataset from systems like SINASC (Live Births Information System) and SIH (Hospital Information System)—researchers tracked 1,821 children exposed in utero to symptomatic maternal chikungunya between 2015 and 2018, matched 1:10 with 18,210 unexposed controls. Follow-up lasted until the child's third birthday, first hospitalization, or study end.

• Adjusted stratified Cox proportional hazards models estimated hazard ratios (HR) for all-cause hospitalization and mortality, accounting for confounders like maternal age, education, race, health access, and municipality.
• Exposure timing was stratified by trimester and intrapartum period.
• Absolute risk differences quantified excess hospitalizations per 1,000 exposed children.

This approach exemplifies CIDACS/Fiocruz's expertise in data integration, a cornerstone of Brazilian public health research often in collaboration with universities like UFBA.

Key Results: Quantifying the 21% Elevated Hospitalization Hazard

The study found a hazard ratio of 1.21 (95% CI: 1.11–1.36) for first hospitalization among exposed children, translating to 37 excess cases per 1,000 (95% CI: 16–64). No strong mortality signal emerged, but hospitalization risks were pronounced based on exposure timing.

These risks persisted even after adjusting for socioeconomic factors, suggesting direct viral or inflammatory impacts.

Timing Matters: Trimester-Specific Vulnerabilities

Early pregnancy exposure (first/second trimester) posed 25–35% higher risks, likely due to fetal organogenesis stages affected by maternal inflammation or viral crossing the placenta. Intrapartum cases doubled the hazard, aligning with high viremia near delivery facilitating neonatal infection. "The results indicate that once the child is exposed to chikungunya as a baby... the disease can have lasting health consequences," notes lead researcher Mio Kushibuchi.

Symptoms may remain subclinical at birth but manifest later, straining Brazil's SUS (Unified Health System) with recurrent pediatric admissions.

Implications Beyond Hospitalization: Neurodevelopment and Morbidity

Prior studies link perinatal chikungunya to neurodevelopmental delays, seizures, and edema in up to 50% of symptomatic neonates. This Fiocruz research extends to long-term all-cause morbidity, urging vigilance for subtle effects like irritability or joint issues persisting into childhood. In Brazil's context—where arboviruses overlap—co-infections amplify risks.

Fiocruz and Brazilian Higher Education's Research Leadership

Fiocruz, Brazil's premier biomedical research powerhouse, collaborates closely with universities like UFBA and international partners like LSHTM. CIDACS exemplifies data science innovation, linking health/social records for population-scale insights. This study builds on Fiocruz's arbovirus legacy, including prior Nature papers on Zika, dengue, and chikungunya perinatal outcomes. Such work positions Brazilian institutions as global leaders in tropical medicine.

Previous Fiocruz Insights on Arboviral Pregnancy Risks

A companion 2025 Fiocruz study in Nature Communications showed maternal chikungunya triples preterm birth risk and elevates neonatal death odds. Dengue and Zika similarly heighten adverse outcomes, emphasizing integrated surveillance. Fiocruz's ArboAlvo project aids vector control nationwide.

Prevention: Protecting Mothers and Babies from Chikungunya

• Use EPA-registered repellents safe for pregnancy (DEET up to 30%).
• Wear long sleeves/pants during peak mosquito hours (dawn/dusk).
• Eliminate standing water to curb Aedes breeding.
• Prenatal screening and monitoring in endemic areas.
• Community vector control, per Brazil's Ministry of Health guidelines.

No vaccine or antiviral is pregnancy-approved, but prevention averts 90% of cases. Consult Fiocruz recommendations for at-risk populations.

Climate Change Fuels Chikungunya Expansion

Warming temperatures and erratic rains expand Aedes habitats, with Fiocruz warning of re-urbanization and sylvatic cycles. Brazil's Northeast bears 60% of cases; projections show 20% rise by 2050 without mitigation.

Public Health Actions and Future Directions

Enhance SUS pediatric follow-up, fund surveillance, and integrate into prenatal protocols. Future Fiocruz research eyes neurocognitive cohorts and vaccines. This study calls for equity-focused interventions in favelas.

Brazilian higher education drives solutions; explore research positions advancing tropical health.

Photo by Artem Beliaikin on Unsplash