11 Nov 2024
Decoding the Oropouche Virus
Recent outbreaks of the Oropouche virus (OROV) in South America have raised health concerns, as the virus has been detected in new areas where transmission had not been previously reported. The Australian Department of Foreign Affairs and Trade (DFAT) has advised travellers to affected regions in South America to exercise caution.
In 2023, South America experienced major outbreaks of OROV. By mid-October 2024, the Pan-American Health Organization (PAHO) reported over 10,000 confirmed cases across the Americas and Europe, with the majority recorded in South America, including more than 8,000 infections in Brazil. Cases linked to travel from regions with ongoing outbreaks have also been identified in the USA, Canada and Europe.
The Royal Melbourne Hospital’s Dr Chuan Lim Kok, a Medical Virologist and Acting Director of the Victorian Infectious Diseases Reference Laboratory (VIDRL) at the Doherty Institute, explains key facts about the virus.
What is the Oropouche virus?
OROV is a re-emerging arbovirus, meaning it spreads to humans and animals through bites from infected mosquitoes, ticks and midges, particularly the Culicoides paraensis species. Although rarely fatal, the virus can cause significant discomfort.
In non-urban environments, OROV is transmitted between mosquitoes and animals such as sloths, monkeys and birds. While the virus has been found in semen, there are currently no reports of direct human-to-human transmission.
Most common in Central and South America, the virus can cause large outbreaks, especially in urban areas.
Signs and symptoms - what to look out for
Symptoms of OROV infection typically appear within three to 10 days of exposure. Common signs include fever, headache or muscle pain (myalgia), many of which resemble the symptoms of Dengue or Chikungunya viral infections.
Occasionally, infected persons may experience pain behind the eyes (retroorbital pain) or develop a red rash with flat and raised parts (maculopapular rash) starting centrally from the body and spreading to the limbs.
Most symptoms are typically short-lived, usually resolving within a week, but they can sometimes recur after a few days to a few weeks.
In rare cases, severe complications such as meningitis, encephalitis and Guillain-Barré syndrome, a disorder in which the immune system mistakenly attacks the peripheral nerves, have been reported in Cuba, along with fatalities in some instances. Pregnancy complications, like foetal death and congenital disorders linked to mother-to-baby transmission, are also being investigated.
Currently, there is no antiviral treatment for OROV. Management primarily involves relieving symptoms.
What is the risk in Australia?
OROV’s primary vector, the Culicoides paraensis midge, is primarily confined to the Americas, reducing the likelihood of significant outbreaks in regions like Australia. However, public health officials remain vigilant as environmental changes and global travel could influence the spread of the virus.
Australians travelling to South America are advised to use bite-prevention methods, including insect repellents and protective clothing.
Although reported cases of OROV in South America have decreased in late 2024, future outbreaks are anticipated, given the widespread presence of Culicoides paraensis across both North and South America, raising concerns about the virus potentially spreading to new regions.
Useful resources
- World Health Organization (WHO): https://www.who.int/news-room/fact-sheets/detail/oropouche-virus-disease
- Pan American Health Organization (PAHO): https://www.paho.org/en/documents/epidemiological-update-oropouche-americas-region-15-october-2024
- Smart traveller: https://www.smartraveller.gov.au/destinations