What is Oropouche fever? Symptoms and causes

"Given the good prognosis for recovery, the impact is assessed as low," wrote the European Center for Disease Prevention and Control (ECDC) in a Threat Assessment Brief on August 9, 2024 — but that's specifically for the European region, which has so far only seen imported cases of Oropouche virus.

Of the 19 reported cases in Europe, all are thought to have been imported by travellers who had visited Cuba or Brazil.

It was in the Brazilian state of Bahia where the first two people died from Oropouche fever, the country's health ministry reported July 25, 2024.

The two women, who were both under the age of 30 years, had no comorbidities but had experienced symptoms similar to dengue fever. 

Brazil's health ministry said that until now: "There have been no reports in the world's scientific literature of deaths from the disease." 

Up to late July, Brazil had recorded 7,236 cases of oropouche fever in 20 states, most of which, however, were recorded in Amazonas and Rondônia. In 2023, Brazil recorded about 840 cases.

Oropouche is common in Latin America and the Caribbean. The virus was first detected in Trinidad and Tobago in 1955. But it has been detected in Europe.

Italy reported its first-ever case of Oropouche in June 2024. It was also the first case ever to be detected in continental Europe. 

The patient diagnosed in Italy had recently returned from a trip to the Caribbean, Italian newspaper Il Messaggero reported, citing public health authorities.  

How does Oropouche fever spread?

Oropouche virus disease is transmitted through the bites of infected midges and mosquitos. Although the disease has long been circulating in Central and South America and the Caribbean, some countries have seen a sharp rise in diagnosed cases this year.   

The disease is spreading to other countries that have never detected cases of Oropouche fever before. On June 11, the WHO reported the first-ever outbreak in Cuba.

"This is the first detection of the disease [in Cuba], therefore, the population is likely highly susceptible and there is significant risk of additional cases being detected," the report noted.  

Symptoms similar to dengue

Oropouche fever is caused by the Oropouche virus, which is transmitted most often through the bite of the Culicoides paraensis midge.

There is no evidence of human-to-human transmission of the disease  — to date.  

Symptoms of the disease are similar to dengue and typically start between four and eight days after the bite.

The onset is sudden, and symptoms usually include fever, headaches, pain, chills, joint stiffness and sometimes nausea and vomiting.

Most patients recover in about seven days. According to the WHO, severe cases are rare.  

There is no specific vaccine or antiviral treatment available for the disease. 

Climate may play a role in spread of Oropouche

Oropouche fever is an understudied illness, as the authors of a May 2023 paper published in the journal Infectious Diseases of Poverty noted. As a result, the disease's epidemic potential and areas of likely spread remain "unexplored."

Although most cases of Oropouche fever thus far have been linked to tropical climate conditions, the authors noted that the lack of available data makes it difficult to draw precise conclusions. For example, some outbreaks have occurred outside the tropical conditions typically associated with transmission events.  

Although much remains unclear about the virus and its spread, the authors also noted that vegetation loss and deforestation appear to be associated with outbreaks of the disease.  

Edited by: Patricia Szobar

Sources:

Oropouche virus disease — Cuba, World Health Organization, June 11, 2024 https://www.who.int/emergencies/disease-outbreak-news/item/2024-DON521

Transmission risk of Oropouche fever across the Americas, published by Romero-Alvarez D, Escobar LE, Auguste AJ, Del Valle SY, Manore CA in the journal Infectious Diseases of Poverty (May 2023) https://idpjournal.biomedcentral.com/articles/10.1186/s40249-023-01091-2

Ministério da Saúde confirma dois óbitos por oropouche no país (Brazil, Ministry of Health, July 25, 2024) https://www.gov.br/saude/pt-br/canais-de-atendimento/sala-de-imprensa/notas-a-imprensa/2024/ministerio-da-saude-confirma-dois-obitos-por-oropouche-no-pais

This article was originally published June 25, 2024, and updated July 29, 2024, to reflect developments in Brazil, where at least two people died from Oropouche — a further death was being investigated for Oropouche fever at the time of publication; one other death had been ruled out. The last update was August 12, 2024, to include detail from a ECDC Threat Assessment Brief.