The Virulent Viral Sextet: #4 - Oropouche
The Oropouche River flows through Trinidad and Tobago, known for its clarity and hikes along the rock formations on its banks. Yet it is now known for something much more dangerous: the Oropouche virus.
What Is Oropouche?
Named for the village where it was first discovered in 1955, Oropouche—also called sloth fever--is an arbovirus (caused by insect bites) endemic to South America and has also been found in Central America and the Caribbean.
It is spread by infected midges, Culicoides paranesis, a type of small fly, that have bitten infected animals (like sloths, rodents, and birds) and which then transmit the virus when they bite you; more rarely, it is spread by mosquitoes. It is not transmissible from person to person.
Typical symptoms are similar to the seasonal flu, dengue, and other arboviruses with an incubation period of 3-10 days causing:
Sudden onset of fever
Headache (can be severe)
Chills
Aches and pains
Joint stiffness
Sensitivity to light and/or eye pain
Dizziness
Nausea and vomiting
A rash that starts on the trunk and goes to the extremities.
Less common symptoms can include conjunctival injection (red eyes), diarrhea, severe abdominal pain, and hemorrhagic symptoms (bleeding from the nose or gums, blood in the stool, severe menstrual bleeding, and petechiae, which are small, round, flat areas of bleeding under the skin or mucous membranes).
Symptoms tend to last for a few days and up to 2 weeks, but it can take a while to recover fully. Oropouche is rarely fatal, but can be dangerous for pregnant women and lead to severe complications in the fetus. What’s also dangerous is that up to 60% of patients can relapse with their prior symptoms a few days or even weeks later.
In about 4% of cases, neuroinvasive disease can occur with meningitis and/or encephalitis symptoms (inflammation of the meningeal sac surrounding the brain, or brain itself). This can cause intense pain in the back of the neck with neck stiffness, dizziness, confusion, lethargy, photophobia, nausea, vomiting, and nystagmus (rapid uncontrollable eye movements). The triad of low white cell counts, low platelet counts, and/or elevated liver functions with occasional meningitis and encephalitis symptoms can also be seen in certain tick-borne viral infections (Heartland, Bourbon virus) as well as tick-borne bacterial infections including Ehrlichia, Anaplasma, Rickettsial infections (Rocky Mountain Spotted Fever, Q-fever), as well as relapsing fever Borrelia like Borrelia miyamotoi. It is also rarely seen in Babesiosis. That is why the Medical Detective must be on the alert to these atypical signs and symptoms and consider treating with doxycycline until a full differential diagnostic work-up has been completed.
Preliminary diagnosis is based on clinical symptoms, and places and dates of travel. Toward the end of the first week of illness, IgM antibodies form, followed by IgG antibodies and occasionally viral RNA (PCRs), so confirmation of a recent infection requires documenting a 4-fold or greater change in antibody titers. Specimens should be sent to your local health department and the CDC to do the testing, since Oropouche IgM and IgM antibody testing is not available through local laboratories.
How Is Oropouche Treated?
There are no vaccines to prevent Oropouche. There are no classic antivirals or any other medicines to treat it either. The only way to avoid Oropouche is to protect yourself with bug spray to avoid getting bitten.
Those with typical symptoms should treat it like the flu—bed rest, pain relief, staying hydrated.
Pregnant women should see their doctor immediately.
For more information on OTC treatments, refer to last week’s Medical Detective Substack on Dengue.
Why Is Oropouche Now in the News?
Cases in Oropouche has recently gone from a few hundred to over 8,000 cases in several South American countries, and for the first time, 2 deaths in previously healthy women in the thirties were reported. In May 2024, Cuba reported outbreaks in two provinces; subsequently, 21 Americans who had visited Cuba this summer returned with infections, almost all of them in Florida. Because symptoms take a while to appear, you can assume that many other cases will appear in travelers returning home after staying in countries with countless infected midges. As of September 17, 2024, the CDC reported that there have been 74 cases in 5 states in America this year. One case also recently appeared in NY, which is why the NY State Department of Health sent out an advisory to healthcare providers at the end of August, warning that this viral infection is spreading and can mimic other infections: “Large outbreaks of dengue virus are occurring in many areas with reported Oropouche virus transmission. Over 165 people with travel-associated dengue have been reported in New York including New York City; it is important to rule out dengue virus infection in travelers with suspected Oropouche virus infection because these viruses cause similar clinical presentations, and early clinical management of dengue can improve patient outcome. Other diagnostic considerations in addition to dengue include chikungunya, leptospirosis, malaria, and infections caused by various other bacterial or viral pathogens.”
This is the fourth viral pathogen of a sextet that is now spreading (bird flu, dengue and mpox being the prior 3; see our past Medical Detective Substacks for more information), and because midges are a global annoyance --it is impossible to eradicate them--we can expect to see more about Oropouche virus in the news in months/years to come. Why?
According to Professor Stephen Graham, School of Biological Sciences Infection and Immunity Theme Leader and Professor of Virus: Host Interactions, University of Cambridge, as reported in the London-based Science Media Centre, “The virus has an RNA genome, like SARS-CoV-2, which means that it is capable of rapid mutation. It also has a genome with multiple segments, like influenza. This means that if you are unlucky enough to be infected with two different strains of the virus they can ‘reassort’ their genome segments, like shuffling two decks of cards together, and you might end up with a new virus strain that is more transmissible and/or more pathogenic. This is what appears to have happened recently in Brazil to launch the current outbreak.”
As ever, climate change is one of the very likely culprits for this sudden increase in new (or old) viral infections like Oropouche, considering that bird flu, dengue, mpox, and West Nile virus are also spreading. We know that higher temperatures increase the reproductive rate of insects, which is likely playing a role. The midge carrying Oropouche might then be able to establish itself in the US, Europe, and Asia, with potentially dire consequences.
If you’re planning to travel to South America, the Caribbean, or Cuba, be sure to pack the bug spray--and don’t forget to use it! The EPA recommendations are picaridin, DEET, oil of lemon eucalyptus (not for children under 3), or products that contain the active ingredient IR3535. Healthcare providers should council pregnant patients planning on visiting endemic areas about the risks of vertical transmission of this virus to the fetus, causing congenital abnormalities or fetal death. As per the CDC, pregnant patients should “consider the destination, reason for traveling, and their ability to prevent insect bites.”
What About Other Mosquito-Borne Viruses?
There are several of viruses carried by mosquitoes which have long plagued the world, most notably malaria, which continues to kill over 600,000 people each year. In the next Substack, I’ll discuss West Nile virus and Eastern Equine Encephalitis, one of the 3 varieties of mosquito-caused encephalitis (the other 2 are St. Louis and Japanese).
Due diligence is a must to check on any outbreaks in areas you might be visiting.
Stay tuned for next weeks Medical Detective Substack on EEE and West Nile, when we discuss the final sextet of spreading viral infections, as well as some potential treatments/immune support you need to know about!