Sexual Transmission of Oropouche Virus Latest Disease Vector to Raise Concerns among Scientists in US and Beyond
Endemic in the Amazon region, recent spread of the disease caused the CDC to issue recommendations to travelers who develop symptoms after visiting certain countries
Anatomic pathologists, microbiologists, and clinical laboratories active in infectious disease testing will want to stay informed about the worldwide progression of the Oropouche virus. The infectious pathogen is spreading beyond the Amazon region (where it is endemic) into more populated areas—including the US—and possibly being transmitted in novel ways … including through sexual activity.
In research published in Emerging Infectious Diseases (a CDC journal) titled, “Replication-Competent Oropouche Virus in Semen of Traveler Returning to Italy from Cuba, 2024,” researchers with the IRCCS Sacro Cuore Don Calabria Hospital in Negrar di Valpolicella, Italy, and the University of Brescia, Brescia, Italy, shared findings about the “potential for person-to-person transmission of Oropouche via sexual encounters.”
The researchers noted 9,852 Oropouche cases as of December 2024.
“This is a very big development,” Tulio de Oliveira, PhD, director of the Center of Epidemic Response and Innovation (CERI) at Stellenbosch University, South Africa, told NPR. “This could open a new route of transmission,” he added.
According to the Centers for Disease Control and Prevention (CDC) no vaccines or medicines exist for the treatment of prevention of Oropouche infection.
The virus primarily spreads to people through biting small flies called midges (a.k.a., no-see-ums), according to a CDC Health Alert Network (HAN) Health Advisory, which added that mosquitoes can also spread the disease.
Oropouche infections, the CDC said, are occurring in Brazil, Bolivia, Peru, Columbia, and Cuba. Cases identified in the US and Europe seem to be among travelers returning from those countries. Reported cases also include deaths in Brazil and cases of mother-to-child (vertical) transmission.
There is “an increase in Oropouche virus disease in the Americas region, originating from endemic areas in the Amazon basin and new areas in South America and the Caribbean,” CDC noted in its Health Advisory.
Though de Oliveira notes that a global outbreak is not yet expected, researchers are nevertheless raising the alarm.
“The challenge is that this is such a new disease that most clinicians—including infectious disease specialists—are not aware of it and we need to make more patients and healthcare providers aware of the disease and increase access to diagnostics so we can test for it,” said David Hamer, MD (above), infectious disease specialist and professor, global health, at Boston University School of Public Health, in an NPR article. “Over the next year, we are going to learn a lot more.” Pathologist, microbiologists, and clinical laboratories will want to keep an eye on the spread of the Oropouche virus. (Photo copyright: Boston University.)
Risks to Pregnant Women, Seniors
Research published in The Lancet Infectious Diseases estimates up to five million people in the Americas are at risk of exposure to the Oropouche virus. The authors also pointed out that cases in Brazil swelled from 261 between the years 2015 to 2022 to 7,497 by August 2024.
About 60% of people infected with Oropouche have symptoms such as fever, chills, headache, muscle aches, and joint pains, according to the CDC Health Advisory, which added that the symptoms generally appear three to 10 days after exposure.
Those with the highest risk of complications from the disease, according to the CDC, include pregnant women, those over age 65, and people with medical conditions such as:
“The geographic range expansion, in conjunction with the identification of vertical transmission and reports of deaths, has raised concerns about the broader threat this virus represents in the Americas,” an additional paper in Emerging Infectious Diseases noted.
Cases of fetal loss and congenital abnormalities (birth defects) in Brazil and Cuba have been reported to the CDC by the Pan American Health Organization (PAHO).
“Healthcare providers should be aware of the risk of vertical transmission and possible adverse impacts on the fetus including fetal death or congenital abnormalities,” CDC said in an Oropouche Clinical Overview statement.
“There have been a few cases of maternal to fetal transmission, and there are four cases of congenital Oropouche infections that have been described—all of which led to microcephaly, which is a small head size,” David Hamer, MD, infectious disease specialist and professor global health, Boston University School of Public Health, told NPR.
Diagnostic Testing at Public Labs
Clinical laboratories and physicians should coordinate with state or local health departments for Oropouche virus testing and reporting.
Health departments are performing “real-time reverse transcription-polymerase chain reaction (RT-PCR) tests to detect viral RNA and/or plaque reduction neutralization testing to detect neutralizing antibodies of serum and/or cerebrospinal fluid,” a CDC Updated Interim Guidance statement explained.
People should consider Oropouche virus testing if they have traveled to an area with documented or suspected cases, have symptoms including fever and headache, and have tested negative for other diseases, especially dengue, according to CDC.
Taking Precautions after Sex
“This [possibility of sexual transmission] brought up more questions than answers,” Hamer told NPR, adding, “we know now is that sexual transmission could happen.”
Though no documented cases of sexual transmission have been recorded, the CDC nevertheless published updated interim guidance, “recommending that male travelers who develop Oropouche symptoms after visiting areas with Level 1 or 2 Travel Health notices for Oropouche to ‘consider using condoms or not having sex for at least 6 weeks’ from the start of their symptoms,” NPR reported.
“Because stillbirths, birth defects, and severe complications and deaths in adults have been reported, CDC is providing interim recommendations on preventing possible sexual transmission based on what we know now,” the CDC stated.
Clinical laboratory leaders working with infectious disease colleagues can help educate physicians and the community about the Oropouche virus and the need to prevent bites from midges and mosquitoes by using, for example, Environmental Protection Agency (EPA) registered insect repellant.
Diagnostics professionals will want to stay abreast of developing Oropouche cases as well as changes to or expansion of clinical laboratory testing and reported guidance.
—Donna Marie Pocius
Related Information:
Increased Oropouche Virus Activity and Associated Risks to Travelers
Replication-Competent Oropouche Virus in Semen of Traveler Returning to Italy from Cuba, 2024
It’s a Virus You May Not Have Heard of. Here’s Why Scientists Are Worried about It
Oropouche Fever: Reports of Vertical Transmission and Deaths in Brazil
Clinical Overview of Oropouche Virus Disease
Updated Interim Guidance for Health Departments on Testing and Reporting for Oropouche Virus Disease
