What is sloth fever and why is it in the news?

“Sloth fever” or oropouche is a viral disease of Sloths and non-human primates and transmitted to humans via the bite of a midge or potentially a mosquito. Birds are also a reservoir.

This makes it one of several insect-borne illnesses that can jump between animals and humans, a pattern becoming more common in global health.

When do outbreaks happen?

Outbreaks often occur during the rainy season.

This is the time when biting insect populations are at their peak, creating more opportunities for transmission.

Oropouche Case Numbers 2024

Oropouche is a vector-borne disease and considered to be a “neglected” global public health threat.

More than 8,000 cases have been reported in Brazil, Bolivia, Colombia, Cuba and Peru during 2024.

It is likely that the disease is grossly underreported given its similar presentation to other febrile illnesses like dengue fever, zika, and chikungunya. Because symptoms overlap, many infections are likely missed or misclassified.

Symptoms

Oropouche disease is usually self-limiting with a good prognosis.  Fatal outcomes are very rare.

Typical symptoms include fever, headache, muscle aches and sensitivity to light, usually lasting several days before resolving.

Cases in returned travellers

Several cases have been identified in travellers after returning home to the Canary Islands, United States, Italy and Germany.  Most of these had travelled to Cuba.

These imported cases highlight how quickly tropical viruses can cross borders through international travel.

European risk assessment

A threat assessment was undertaken by the European Centre for Disease Prevention and Control. It concluded the risk of exposure in epidemic areas of South and Central America is moderate.

The report also raised concerns of oropouche infection in pregnant women. These concerns are very similar to those noted with zika infection. This requires further investigation. The report is available at ECDC.

Oropouche treatment and prevention

There is no specific treatment for the Oropouche disease. Brush up on your insect avoidance measures before travel.

This includes activity modification to reduce exposure time, using repellent, wearing long clothing and sleeping under treated bed nets in risk areas.