Technology & Innovation

This tropical virus spreads from the Amazon region to the United States and Europe


Oropouche outbreak The virus has circulated in the Amazon region for decades, but historically the pathogen has caused little inconvenience to the rest of the world. But that seems to be changing. In 2024, the virus showed that it could travel.

Most of the more than 11,000 cases this year occurred in Brazil and Peru, where the virus was previously known, but it was also found in 2024 in Bolivia, Colombia, Ecuador, Guyana, Panama and Cuba – the latter reporting 603 cases. As well as transmission within the country for the first time. Infected travelers have also carried the virus to North America and Europe: this year it has been found twice in Canada and 94 times in the United States – with 90 cases reported in Florida – while 30 imported cases have been found across Spain, Italy and Germany.

For those who study Oropouche and other arboviruses — the family of viruses transmitted by arthropods such as mosquitoes and ticks — the situation is alarming. Although there is evidence about its transmission cycle, there is not enough information to accurately predict Oropouche’s future behavior. “We have some pieces of the puzzle, but there is not complete certainty about the role each piece plays,” says Juan Carlos Navarro, director of research at SEK International University, where he heads the Emerging Diseases and Epidemiology Group.

The first symptoms of the disease appear suddenly three to 12 days after being bitten, and usually last between four and six days. Symptoms include headache, muscle and joint pain, chills, nausea, vomiting, and sensitivity to light. A skin rash, bleeding from the gums or nose, and in severe cases, meningitis or encephalitis – an inflammation of the brain and its membranes – may occur. Oropouche infections are generally uncomplicated, if troublesome, although for the first time this year Brazil recorded two deaths linked to the virus.

And in places where cases have occurred, researchers are increasingly discovering something that may explain why the virus emerged and spread: deforestation. Altering natural land to grow crops, drill for oil or drill for resources “appears to be the main driver of the outbreak,” Navarro says. “It brings together three links: the virus, the vector, and humans.”

A natural cycle with gaps

In 1955, a coal burner fell ill after spending two weeks working and sleeping in the forest near the Oroboche River in Trinidad and Tobago. He had a fever for three days. This was the first documented case of Oropouche virus disease. Since then, dozens of outbreaks have been reported, most of which occurred in the Amazon Basin.

Navarro has devoted 30 years to studying arboviruses such as dengue, equine encephalitis, mayaro, and, since 2016, orobosch. It has two transmission cycles. In the forest, reservoirs of the Oropouche virus — animals that keep the virus spreading, even if they don’t get sick — are thought to be non-human primates such as neotropical marmosets and capuchin monkeys, sloths, rodents, and birds. The virus has been isolated from these creatures or antibodies have been found in their systems. In fact, this disease is also known as “sloth fever.” Navarro says it’s not understood what role sloths and non-human primates play in the transmission cycle. “They are likely amplifying the hosts” — meaning they are likely allowing the virus to rapidly replicate to high concentrations in their bodies.

When there is an epidemic among humans, there is a second cycle of transmission. In this, humans are the amplifying host, and the virus is transmitted among them via blood-eating insects. The main vector that transmits the pathogen between humans is the fly colicoides barrensis, It is the size of a pinhead and is found from Argentina to the United States. Some studies suggest that Culex and Aedes mosquitoes can also transmit Oropouche. In fact, the first isolation of the virus in Trinidad and Tobago was from… coquiletidae Venezuela, Another type of mosquito.

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