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According to research from the Centre for Data and Knowledge Integration for Health (CIDACS), Oswaldo Cruz Foundation (Fiocruz), Salvador, Bahia, Brazil, maternal chikungunya infection during the first trimester was associated with a 25% increased risk of the infant being hospitalized within the first 3 years of life, and infection during the second trimester was associated with a 35% increased risk. The study was published in March in the journal Nature Communications.

“We already knew that maternal‑fetal transmission of chikungunya is rare during most of pregnancy, but now we also know that the highest risk occurs at delivery, when mothers are in the viremic phase — which can occur in up to 50% of cases — and often causes severe disease in newborns,” said Marco Aurélio Palazzi Sáfadi, MD, PhD, chairman of the Department of Infectious Diseases of the Brazilian Society of Pediatrics. “This study shows that, even outside that context, maternal infection early in pregnancy can also have important consequences for the child’s health, which requires heightened attention in pediatric care,” he said.

Mio Kushibuchi, MD, a postdoctoral researcher at Cidacs/Fiocruz and the study’s lead author, said researchers followed 1800 children born to women who had chikungunya during pregnancy between 2015 and 2018 using data from the Live Birth Information System, the SUS Hospital Information System, the Mortality Information System, and the Cadastro Único (Brazil’s registry for access to social programs for low‑income families). Another 18,210 unexposed children were matched as controls. The study captured maternal age, education, maternal race, access to health services, municipality of residence, and date of birth. “It was one of the largest cohorts of its kind in the world for chikungunya,” Kushibuchi said. 

Follow‑up from birth to age 3 showed a 21% higher risk of hospitalization when exposure to chikungunya occurred in utero. The risk was twice as high when the mother was viremic at delivery. Kushibuchi noted that despite the large number of children observed, the study could not determine the causes of hospitalization or the neonatal death rate. “Ideally, there would be follow‑up to see how these children fared after hospitalization, but that will have to be studied in the future with a larger data set and longer follow‑up,” she said. 

One of the study’s co-authors, Viviane Boaventura, MD, PhD, a researcher at Oswaldo Cruz Foundation and a professor at the Federal University of Bahia, said one difficulty in identifying chikungunya’s impact on children is that they may not show visible sequelae at birth. She said they always investigate disease history in areas with higher case counts, but it is not routine in prenatal screening. 

Following this study, Kushibuchi recommends laboratory testing in prenatal care for the three main arboviruses — Zika, chikungunya, and dengue — and if any test is positive, ensuring closer follow‑up of the child throughout childhood. She said it is now clear that not only Zika but also chikungunya can affect long‑term health even when there are no obvious signs at birth.

Boaventura said that ideally women of reproductive age should be vaccinated against chikungunya before becoming pregnant. There should be formal guidance on this, especially in places where the disease is endemic or where outbreaks are frequent.

In April 2025, the Brazilian Health Regulatory Agency approved a chikungunya vaccine produced by the Butantan Institute in partnership with the Franco‑Austrian company Valneva. Because it is a live‑attenuated vaccine, it is not recommended for people who are immunocompromised, those with certain comorbidities, or for pregnant or breastfeeding women.

The vaccine is being rolled out in a pilot program in selected municipalities in the states of São Paulo, Sergipe, Ceará, Mato Grosso do Sul, and Minas Gerais. Localities were chosen based on an epidemiological study that used a mathematical model to identify areas at higher risk for chikungunya outbreaks between 2025 and 2027. The Butantan Institute will monitor both positive and negative cases in the participating municipalities and compare outcomes between vaccinated and unvaccinated populations.

The Disease 

Chikungunya typically presents with high fever and severe joint pain, and about 30% to 50% of patients go on to develop chronic symptoms. “The pain is so severe that many people self‑medicate with anti‑inflammatories and corticosteroids, which is dangerous because it can lead to gastrointestinal, metabolic, and kidney problems,” warned Boaventura. Moreover, pregnant women with comorbidities such as diabetes or hypertension may be at increased risk of decompensation of those conditions.

Clinicians should therefore be alert to any warning signs and closely monitor pain‑control medication use. “There is no antiviral medication — only supportive care — and, as with dengue, it is important to maintain adequate hydration and careful analgesia to avoid iatrogenic harm and complications,” she added. Neurological and cardiovascular manifestations are associated with more severe forms of the disease.

Brazil is the epicenter of chikungunya in the Americas, accounting for about 96% of confirmed infections in the region, according to the Brazilian Society of Tropical Medicine. Brazil’s Ministry of Health Arbovirus Dashboard reported that in 2025, the disease infected about 129,000 people and caused at least 120 deaths. 

How to Address the Problem

After reviewing the study, Alexandre Naime Barbosa, MD, PhD, head of the Department of Infectious Diseases at São Paulo State University, São Paulo, Brazil, concluded that pregnant women with chikungunya should be regarded as higher-risk pregnancies. He also noted that arboviral infections disproportionately affect lower‑income populations and that higher hospitalization rates in these groups may reflect greater infection burdens, so potential causal links require further investigation.

Given the epidemic spread of chikungunya announced by the Pan American Health Organization and the World Health Organization in February 2026, and the worsening climate crisis that favors the proliferation of the Aedes aegypti mosquito, and because the vaccine is not yet available to the entire population, Barbosa emphasized that prevention should rely on classic methods: vector control, use of repellents, installing window screens, and wearing clothing that reduces skin exposure. 

“With this study, we now know that children exposed to chikungunya in utero need ongoing monitoring. Treating this disease as a public‑health priority is urgent,” Barbosa said. 

This story was translated from Medscape's Portuguese edition.