What is the Oropouche virus? New Threat Sparks Concerns.

A little-known disease transmitted through insect bites has become deadly, prompting health officials to issue warnings.

What is Oropouche virus? Emerging Threat Raises Concerns
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As of August 1, more than 8,000 cases of Oropouche virus have been reported this year. Most of these cases have occurred in South America, but the virus is also appearing in countries where it hasn't been seen before, and there have been numerous travel-related cases in the United States and Europe.

The Pan American Health Organization (PAHO), a branch of the World Health Organization, has issued an epidemiological alert for the Oropouche virus and elevated the public health risk to "high" for the Americas.

"Although the disease has historically been considered mild, the spread of transmission to new areas and the emergence of more severe cases highlight the need for increased surveillance and investigation of possible severe manifestations," the agency stated.

The U.S. Centers for Disease Control and Prevention (CDC) has also released a health advisory, urging healthcare providers and public health officials to monitor for new cases and advising pregnant women to avoid traveling to affected areas.

The CDC reported that at least 21 U.S. travelers returning from Cuba have tested positive for the Oropouche virus.

What is Oropouche Virus?

The Oropouche virus was initially discovered in 1955 in the village of Oropouche in Trinidad and Tobago. Since then, around 500,000 cases have been recorded, though the disease remains poorly understood, with The Lancet medical journal recently referring to it as a "mysterious threat."

According to the CDC, about 60% of those infected develop symptoms, which can resemble those of dengue or Zika virus, 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 cases, the virus can infect the nervous system, causing meningitis and encephalitis.

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

"This situation is similar to what we experienced when Zika was first introduced," said Janet Hamilton, executive director of the Council of State and Territorial Epidemiologists. "We don't completely understand the virus's life cycle and transmission, and it seems to impact pregnant individuals, making it essential to gain more knowledge about it."

How Does It Spread?

The virus is transmitted to humans primarily through insect bites, particularly from biting midges (tiny flies) and certain types of mosquitoes. It is endemic to the Amazon basin region of South America, especially in forested areas where the virus is maintained in a cycle between insects and other hosts like rodents, sloths, and birds. It is sometimes referred to as "sloth fever."

People visiting these areas can be bitten by an infected insect and bring the virus back to urban settings.

According to the PAHO, climate change and deforestation increase the chances of human interaction with infected insects, thereby raising the risk of spreading the virus.

The current outbreak is rapidly spreading in both countries where the virus is already present and new areas. Locally acquired cases have been reported in Bolivia, Brazil, Colombia, Cuba, and Peru. There is no evidence of local transmission in the United States, but several cases have been reported in travelers returning from affected regions.

The current risk of sustained local transmission in the continental U.S. is considered low, according to Dr. Erin Staples, a medical epidemiologist with the CDC’s Division of Vector-Borne Diseases. However, the risk level is less certain in areas like Puerto Rico and the U.S. Virgin Islands, which may have similar ecological conditions to Cuba.

What’s Happening Now?

Experts suggest that changes in the virus's geographic spread may indicate new vectors in the transmission cycle.

"We need more information to better understand which areas might be at risk," Staples said. "We are still learning about this virus and will provide updates as they become available."

This year is the first time that deaths have been reported from the Oropouche virus, and it's also the first time evidence has shown that the virus can be transmitted from a pregnant woman to her fetus, potentially leading to negative birth outcomes.

Earlier this year, Brazil reported the deaths of two young women who were otherwise healthy and not pregnant. A third fatal case in a middle-aged man is under investigation by PAHO.

Additionally, there have been at least five cases in pregnant individuals that resulted in fetal death or congenital abnormalities, including microcephaly, a rare birth defect characterized by an underdeveloped brain.

According to Staples, some of these severe outcomes may be due to the increased circulation of the virus. "As more people become infected, we may see rare and unusual occurrences of clinical symptoms or death," she said. "The CDC is actively working with our partners to learn more about these developments."

How can people protect themselves?

Currently, there is no vaccine or specific antiviral treatment for Oropouche virus. Diagnosis can be confirmed through laboratory testing, but these tests are not available at commercial diagnostic labs, and more common viruses like dengue often need to be ruled out first.

"This is a good time to think about preventing mosquito bites: Avoid going outside during dawn and dusk when mosquitoes are most active, wear clothing that protects your skin from mosquito and insect bites, and use mosquito repellent that is effective at preventing infections," said Hamilton.

The CDC has issued two travel advisories: one advises travelers to South America to take "usual precautions," and the other recommends that those traveling to Cuba take "enhanced precautions" to protect themselves from insect bites and to seek medical care if needed.

Experts also emphasize that pregnant women should be particularly cautious. The CDC advises pregnant individuals to reconsider nonessential travel to Cuba.

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