A little known, but potentially lethal virus is spreading throughout Latin America and the Caribbean, prompting the US Centers for Disease Control (CDC) and other health agencies to issue warnings for travelers and clinicians.

Oropouche virus, an arbovirus like dengue, Zika, and chikungunya, is spread through certain midge or mosquito bites. Oropouche symptoms are similar to these other arboviruses with fever, rashes, muscle aches, and headaches common. Symptoms typically last 5 to 7 days, but more recently, the virus has been linked to severe fetal outcomes, including congenital abnormalities and death. 

While the virus was first detected in 1955 in the Caribbean nation of Trinidad and Tobago, the Americas saw few cases each year – and those that were reported were mostly concentrated in the  Amazon or other rainforests.  

Now, however, Oropouche cases have jumped dramatically. The Pan-American Health Organization (PAHO) has reported 8,078 confirmed cases since January – almost a ten-fold increase since last year – with Brazil’s endemic Amazon regions contributing most to the case count. Other countries, like Cuba and Bolivia, are reporting cases for the very first time.

Despite ongoing research, much about Oropouche virus remains unknown, including the factors behind this year’s unusually severe outbreak, which prompted The Lancet to label it a “mysterious threat.” Historically, no Oropouche-attributed deaths have occurred since the virus was discovered, yet this year has already seen the deaths of two otherwise healthy Brazilian women. 

PAHO notes that “although the disease has historically been described as mild, the geographic spread in transmission and the detection of more severe cases underscore the need for increased surveillance and characterization of possible more severe manifestations.”

Vertical transmission reported, travel-associated cases

Brazil was the first country to report instances of vertical transmission – when a disease passes from mother to fetus – earlier this summer. The latest epidemiological alert notes four cases of infant microcephaly, and four suspected fetal deaths. 

The CDC has thus urged pregnant women to reconsider nonessential travel to Cuba and if unavoidable to strictly follow the CDC’s prevention recommendations, which include using insect repellent, and window and door screens. These recommendations also work to prevent dengue, which has so far caused over 10 million cases in the Americas, including the US territory of Puerto Rico. 

The CDC’s alert comes as a response to several travel-associated cases in the US and Europe, mostly from individuals returning from Cuba and Brazil. No local transmission has been reported in the US or Europe.  

Climate change, deforestation, mutations, possible culprits

The CDC report came just a few days prior to World Mosquito Day, in which the World Health Organization has called for member states to intensify their awareness of the dangers posed by mosquito-borne diseases. 

Climate change, deforestation, and unplanned urbanization are facilitating Oropouche’s march through Latin America and the Caribbean, PAHO noted in its analysis. As in many cases, these trends help facilitate the leap of vector-borne diseases that were previously prevalent mostly in remote rural areas to cities.

“Oropouche virus has infected people living in regions far from forested areas, thus indicating that an urban cycle can exist as well,” wrote the Lancet editorial team. The authors also speculate that genetic mutations could help explain the rapid increase in cases. Yet the virus’s spread follows a pattern similar to dengue, zika, and chikungunya – the mosquito-borne diseases that have smashed records this year. 

Like many neglected tropical diseases, the actual number of Oropouche cases may be much higher, said PAHO in a recent statement. 

And with Oropouche presenting symptoms similar to other arboviruses, PAHO is urging member states to strengthen epidemiological surveillance and laboratory diagnosis, particularly to identify fatal and severe cases and possible cases of vertical transmission. The organization also urges countries to “expand prevention campaigns and strengthen entomological surveillance and vector control actions to reduce mosquito and gnat populations.”

Image Credits: Earth.org, PAHO , PAHO/WHO.