Oropouche: Causes and How It Spreads

Primary cause

Oropouche is caused by a virus that can be found in parts of South America, Central America, and the Caribbean. Oropouche virus is an RNA virus that belongs to the Simbu serogroup of the genus Orthobunyavirus in the family Peribunyaviridae.

There is no evidence that Oropouche virus has been spread in the United States.

How it spreads

Oropouche virus is spread to people primarily by the bite of an infected biting midge (Culicoides paraensis). Biting midges are small flies, often called “no-see-ums.” These biting midges are present in multiple states within the United States.

Some types of mosquitoes can also spread the virus, including Culex quinquefasciatus, Coquillettidia venezuelensis, and Aedes serratus mosquitoes. Culex quinquefasciatus are the same mosquitoes that can spread West Nile and St. Louis encephalitis viruses.

In urban areas, when people who are infected with Oropouche are bitten, they can spread the virus through their blood to biting midges or mosquitoes. The biting midge or mosquito can then spread the virus to other people. If you’ve recently traveled to an area with Oropouche virus or have Oropouche, you should prevent bites from biting midges and mosquitoes after travel to avoid spreading the virus further.

The virus is not spread from person-to-person through coughing, sneezing, or touching.

Oropouche and possible spread through sex

A recent scientific report describes the first time Oropouche virus was found in semen of a patient who had Oropouche, which raises concern about the possible risk of sexual transmission. Other viruses (like Zika and Ebola viruses) in semen have been associated with sexual transmission of other infectious diseases. No cases of sexual transmission of Oropouche virus have been reported.

Experts do not yet know:

• If people infected with Oropouche virus can spread the virus through sex.
• If it can be spread through sex, how long people might be able to spread Oropouche virus through sex.
• If spread of Oropouche virus during sex could cause a risk to pregnancies.
• If Oropouche virus is found in vaginal fluids or has any effect on male fertility.

CDC has interim recommendations for travelers to areas with a Level 1 or 2 Travel Health Notice for Oropouche to prevent possible transmission during sex.

Transmission cycle

Transmission of Oropouche virus is maintained in a sylvatic cycle in forested areas between mosquitoes and non-human vertebrate hosts, possibly including three-toed sloths, certain non-human primates, and birds. Mosquitoes suspected of playing a role in sylvatic transmission include Coquillettidia venezuelensis and Aedes serratus.

Oropouche virus is most likely brought from a forested area into an urban environment by an infected person. Biting midges are believed to be primarily responsible for transmitting the virus from an infected person to an uninfected person in an urban area. Culex quinquefasciatus have also been implicated as a potential urban vector.

Oropouche virus can also infect people in laboratories. Seven laboratory workers are known to have been accidentally infected with Oropouche virus through aerosolization or ingestion in the laboratory; all developed symptoms.