Stillbirths linked to rare disease in Brazil raises fear of Zika re-run
A poorly-understood virus spreading in South America has been linked to stillbirths and birth defects, raising fears of a re-run of the Zika outbreaks that swept the continent in 2015.
Brazil’s health ministry sounded the alarm over the spread of Oropouche, reporting four cases of microcephaly – where a baby’s head is much smaller than expected – in newborns of mothers infected with the virus, as well as the death of a foetus.
The ministry has advised health professionals to closely monitor infected pregnant women amid warnings of a “looming crisis”.
“Yet again pregnant women and their foetuses are at higher risk,” said Dr Andre Siqueira, a researcher and infectious diseases consultant at the Instituto Nacional de Infectologia Evandro Chagas in Rio de Janeiro.
“It makes it even more worrying to think that these most vulnerable individuals were not only a target for Zika, but that this could be the same for Oropouche… We could be looking at a looming crisis,” he told the Telegraph.
Surging cases of Oropouche, which is part of the arbovirus family that includes the Zika virus and Dengue, were first noted in June.
Brazil has confirmed 6,976 cases this year, several times the number of infections recorded in all of 2023.
Cases have also been reported in Bolivia, Colombia, Peru, and even across the ocean in Cuba.
The virus is spread primarily through culicoides paraensis, a tiny midge found across the Americas, and the Aedes aegypti mosquito that feeds on infected three-toed sloths in the Amazon basin.
Scientists fear Oropouche has the potential to develop into a major outbreak.
The cases reported by the health ministry bear a striking resemblance to Zika infections.
Outbreaks of Zika resulted in more than 3,500 cases of infant microcephaly in Brazil in 2015 and 2016, with an estimated 1.5 million people infected.
Scientists have warned that, as in the early days of the Zika outbreak, cases could be much higher than reported so far due to a lack of testing.
Since early 2024, Brazil has tested just 10 per cent of samples from patients showing symptoms of Oropouche fever who have tested negative for Zika, chikungunya, and dengue.
“Zika has been the key example we’ve had up to now. As for Oropouche… it’s sort of the great unknown at the moment,” said Dr Danny Altmann, a Professor of Immunology at Imperial College London.
Mother-to-foetal transmission
In June, researchers at the Evandro Chagas Institute in Pará conducted a retrospective analysis of stored patient samples from cases of suspected viral infections causing neurological damage. These patients had previously tested negative for other arboviral diseases, including dengue, chikungunya, Zika, and West Nile viruses.
The analysis revealed that four babies born with microcephaly tested positive for antibodies against the Oropouche virus, detected in both their blood and cerebrospinal fluid, which surrounds the brain and spinal cord, indicating direct mother-to-foetus transmission.
Then, earlier this month, the same institute identified and tested a foetus stillborn at 30 weeks of gestation and found Oropouche virus genetic material in the umbilical cord and multiple organs, including the brain, liver, kidneys, lungs, heart, and spleen. Researchers are conducting further investigation and the link has yet to be confirmed.
“The more detailed clinical description, especially of the consequences, has yet to be made so far,” said Dr Siqueira. “We still can’t establish certain causation with these observations, but it’s something that raises a red flag, and worries, because of all the experience with Zika, which could have a similar story.”
Dr Paul Hunter, a professor of medicine at the University of East Anglia, said the association between the infection and foetal death “does appear strong though not definitive”, but that there was “definitely” mother-to-foetal transmission.
Previous studies have indicated that the Oropouche virus can invade the human brain and cause neurological issues. In severe cases, adults may experience brain inflammation, vertigo, and profound fatigue.
The strain behind the recent outbreak was first identified in the village of Oropouche, Trinidad and Tobago, in 1955. Five years later, a sloth was found carrying the virus during the construction of the Belém-Brasília highway. Within a year, Oropouche fever began spreading to people in the area, with around 30 outbreaks reported since, all centred in the Amazon basin.
The current outbreak began in Roraima, northern Brazil, and has spread to the heavily populated East Coast, including Rio de Janeiro, Santa Catarina, Bahia, and Minas Gerais. Only a few patients had travelled to the Amazon basin, indicating local transmission of Oropouche. The remoteness of the suspected point of origin complicates the work of those investigating the outbreak.
“One of the problems in countries like Brazil, especially the areas where these viruses are, historically we know it can be quite difficult to access areas with affected populations as they are rural or remote,” said Professor Alain Kohl, Professor of Virology and Infectious Diseases at Liverpool School of Tropical Medicine.
Professor Altman explained that Oropouche is becoming more of a threat due to climate change, which has encouraged the mosquitos to fly further afield, while increased rainfall and flooding have provided the perfect breeding ground for the insects.
Deforestation and urbanisation also have the potential to displace host animals and cause midges and mosquitoes to feed on humans, rather than wildlife.
Dr Siqueira warned that researchers must apply the lessons learned from the Zika outbreak in the mid-2010s, where testing was also limited and its severity was underestimated.
The virus was first detected in Uganda in 1947, and sporadic outbreaks were recorded in the coming decades, but by 2015 emerged as a major epidemic in Brazil.
“Zika, when it first appeared in Brazil, was not seen as a severe disease that would cause any worry – it had very mild symptoms. But now we know the consequences and the possibilities,” he said. “Now, we need to push to find out earlier what the consequences could be… trying to use the learnings from the Zika emergency.”
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