What is the Oropouche virus? This emerging threat is causing concern among health officials.

A previously little-known disease spread by insect bites has become deadly, prompting health officials to raise the alarm.

As of August 1, over 8,000 cases of Oropouche virus have been reported this year, primarily in South America, but also spreading to areas where it has not previously been seen. Travel-related cases have been identified in the United States and Europe.

The Pan American Health Organization, a regional branch of the World Health Organization, has issued an epidemiological alert for the Oropouche virus, increasing the public health risk level to “high” for the Americas.

Historically considered mild, the disease’s recent geographic spread and more severe cases highlight the need for enhanced surveillance, the agency noted. The CDC has also issued a health advisory urging healthcare providers to be vigilant for new cases and recommending that pregnant women avoid traveling to affected regions.

At least 21 travelers returning from Cuba have tested positive for the Oropouche virus, according to the CDC.

What is Oropouche virus?

Named after a village in Trinidad and Tobago where it was discovered in 1955, Oropouche virus has led to around 500,000 recorded cases. However, knowledge about the virus is still limited, with The Lancet recently labeling it a “mysterious threat.”

About 60% of those infected exhibit symptoms similar to dengue or Zika, including sudden fever, chills, headaches, muscle pain, and joint stiffness. Other symptoms may include eye pain, light sensitivity, nausea, vomiting, diarrhea, fatigue, and rash. In rare instances, the virus can affect the nervous system, causing meningitis and encephalitis.

Though Oropouche virus belongs to a different viral family than Zika, it raises similar concerns.

“This situation resembles the introduction of Zika into this country,” said Janet Hamilton, executive director of the Council of State and Territorial Epidemiologists. “We lack full understanding of its life cycle and its impact on pregnant individuals.”

How does it spread?

Oropouche virus primarily spreads through insect bites, particularly from biting midges and certain mosquitoes. Endemic to the Amazon basin, especially in forested areas, the virus is maintained through a cycle involving insects and other hosts like rodents and birds. Travelers to these regions can carry the virus back to urban areas.

Factors such as climate change and deforestation increase the risk of human interaction with infected insects, according to the Pan American Health Organization.

Current outbreaks are rapidly spreading in known regions as well as new areas. Locally acquired cases have been reported in Bolivia, Brazil, Colombia, Cuba, and Peru. While there is no evidence of local transmission in the U.S., several cases have emerged in travelers returning from affected areas.

Dr. Erin Staples from the CDC states that the risk of sustained local transmission in the continental U.S. remains low, but it’s uncertain in Puerto Rico and the U.S. Virgin Islands, which share ecological similarities with Cuba.

What’s happening now?

Experts suggest that the shifting geography of the virus could indicate new vectors in the transmission cycle. This year has also seen the first reported deaths associated with Oropouche virus, as well as evidence of potential transmission from pregnant women to their fetuses.

Brazil has reported fatalities in two healthy young women, and a third case involving a middle-aged man is under investigation. There have also been five cases in pregnant individuals leading to fetal deaths or congenital abnormalities like microcephaly.

As more people become infected, unusual clinical symptoms or fatalities may occur, which the CDC is actively monitoring with its partners.

How can people protect themselves?

Currently, there is no vaccine or specific antiviral treatment for Oropouche virus. While laboratory testing can confirm cases, it is not widely available, and other common viruses like dengue must often be ruled out first.

Preventative measures against mosquito bites include avoiding outdoor activity at dawn and dusk, wearing protective clothing, and using effective mosquito repellents.

The CDC has issued two travel advisories: one recommending general precautions for travelers to South America and another urging enhanced precautions for those traveling to Cuba, especially for pregnant individuals.