“…the mysterious insect-borne virus that causes Oropouche fever has been expanding its range since late 2023, raising international concern.”
Mariana Letharo, Nature news reporter
“More than 20 U.S. travelers returning from Cuba have tested positive for Oropouche virus, also named sloth fever, the Centers for Disease Control and Prevention said on Tuesday, as the little known and potentially dangerous disease sparking international concern spreads in South America and to countries where it hasn’t been seen before.”
Robert Hart, Forbes senior reporter
The Oropouche virus, also referred to as “sloth fever virus,” has been causing outbreaks of infection in humans living in the Amazon region for decades. But, this arbovirus wasn’t even on my radar screen until August 16, 2024 when the Centers for Disease Control and Prevention (CDC) issued this health advisory: "Increased Oropouche Virus Activity and Associated Risk to Travelers." Then on August 26, 2024, the CDC ramped up concern with a notification that a case of Oropouche disease (pronounced “oro-poosh”) was reported in New York, further piquing my interest. My goal in this Germ Gems post is to provide a summary of key features of this emerging viral infection.
What is Oropouche fever? Oropouche fever is a viral infection caused by the RNA Oropouche virus, a member of the genus Orthobunyavirus. These viruses differ from other better known vector-borne viruses because they’re typically transmitted to humans by a midge, Culicoides paraensis, rather than by mosquitoes. (Germ Gems posts are rife with stories about RNA viruses that are transmitted by mosquitoes, such as, West Nile virus, dengue virus, and chikungunya virus to name just a few.)
Oropouche virus was discovered in 1955 in the Caribbean in Trinidad and Tobago. In 1960, it was detected in a blood sample from a sloth. Non-human primates, birds, and pale-throated sloths are a reservoirs for Oropouche virus. And even though the virus doesn’t cause illness in sloths, Oropouche virus became popularized as “sloth fever virus.”
What are the symptoms of sloth fever? The symptoms of Oropouche virus infection are similar to those of other arboviruses (insect-borne) infections such as dengue. Symptoms include fever, headache, muscle and joint pain, pain behind the eyes, nausea and vomiting.
Most cases of sloth fever are mild and the illness resolves after seven to eight days. But in a minority of cases, the illness may evolve into more severe forms with neurological or hemorrhagic manifestations. And recent reports of two deaths in previously healthy women as well as reports of vertical transmissions (mother to fetus) of the virus associated with adverse pregnancy outcomes, e.g., stillbirths, miscarriages, and birth defects, have raised the level of concern about the threat the Oropouche virus poses to human health.
Culicodes paraensis, vector of Oropouche virus. Some mosquitoes can transmit the Oropouche virus, but the main vectoris a biting midge called Culicodes paraensis. These midges are one of the most common and abundant organisms in natural and man-made aquatic habitats.
The midge species Culicodes paraensis is found from the northern U.S. to Argentina. In the U.S., these very small gray two-winged insects are nicknamed “no-see-ums” because they are so small that people often feel the bite without seeing the midge.
Range of Oropouche virus infections is expanding. Since the discovery of the Oropouche virus in 1955, 500,000 cases of Oropouche fever have been recorded overall. But the number of cases is rising and the range of the infection is spreading.
According to a report in Nature on August 26, 2024, “Mysterious Oropouche virus is spreading: what you should know,” more than 8,000 human cases have been confirmed in the Americas so far this year. While most of these cases have been in Brazil, Peru, Bolivia, Colombia, and Cuba have also been affected. The article “Oropouche Virus Spreads to New Regions in Latin America,” in an August 30, 2024 publication of the Journal of American Medical Association, details the march of Oropouche virus through Latin America.
Increasing spread of Oropouche virus: why now? Mosquitoes, ticks, and lice are having a field day because of climate change (global warming and flooding). While I haven’t seen any studies of the impact of climate change on midges, I’d hazard a guess that they too are enjoying the effects of what we humans have been doing to heat-up our planet. Hence solutions to the increased threat of climate change on human health will impact not only big problems like hurricanes and wildfires but also will avert challenges from tiny threats like “no-see-ums.”
댓글