Oropouche virus, from South America, a new global threat? “What we see is a chronicle of an announced tragedy”

In a region already plagued by numerous public health challenges, a little-known virus called Oropouche has set off a wave of alarm in South America. Researchers and public health experts point out that this virus is spreading quickly and that humans are the main driver of this epidemic.

Deforestation in the Amazon area contributes to the spread of the Oropouche virus – Photo Shutterstock

Oropouche virus is causing concern in South America. Brazil recorded 5,530 cases this year, up from 836 in all of 2023. Similar increases were also reported in Bolivia, Colombia and Peru. The virus, traditionally endemic to the Amazon basin, is now also affecting areas outside the rainforest. Cuba reported its first cases in May, according to the journal Science.

A major concern is the possibility that this mosquito-borne virus could cause a major epidemic in Latin America, which is already experiencing outbreaks of Zika, chikungunya, a viral disease, and dengue.

Symptoms are generally mild, but the virus can also cause severe neurological complications. Even a mild epidemic poses an additional threat to health systems in the region.

What worries us most is the spread of a disease that was virtually confined to the Amazon, which has a very low population density, into areas with a higher population densityi”, says Marcus Lacerda, researcher in the field of infectious diseases at the Oswaldo Cruz Foundation (Fiocruz), according to the cited source.

The Oropouche virus, first identified in Trinidad and Tobago in 1955, evolved through genetic modification a decade ago. It initially spread in the Amazon rainforest, circulating among primates, sloths and birds. Urban transmission is via the insect Culicoides paraensis, and the first cases in the current outbreak were detected in Roraima, Brazil, in late 2022. Since then, the disease has spread to populated areas in eastern Brazil. Symptoms are similar to those of other tropical diseases, making diagnosis difficult.

Chronicle of an announced tragedy

To the few researchers who study Oropouche fever, the spread of the virus outside its endemic region was no surprise. Since the early 2000s, the virus has started to spread more and more, a fact confirmed by Socorro Azevedo of the Evandro Chagas Institute in the Brazilian Amazon.

What we see is a chronicle of an announced tragedy“, she says.

Increased human movement between forest and urban areas could contribute to the spread of the virus, researchers believe. Deforestation is also believed to be a major factor, displacing the animal hosts of the virus and prompting the flies to feed on humans instead of livestock.

It should be emphasized that the whole man is to blame in this case too! Deforestation and all the destructive actions of man vis a vis nature lead to imbalances of all kinds and the transfer of various viruses from wild animals to humans. There is thus a risk that these viruses will adapt to the human species as SARS CoV 2 did and generate even major public health problems.”, explained Dr. Emilian Popovici, vice-president of the Romanian Society of Epidemiology, for “truth“.

However, Dr. Emilian Popovici emphasized that “we should not be afraid“, for now.

In Manaus, the capital of Amazonas state, the first cases were reported in recently deforested areas. Satellite images confirm this connection. Climate change, with higher temperatures and increased precipitation, could accelerate the reproduction of insects and, by extension, the spread of the virus.

In several locations where the virus has been detected in South America, we have consistently detected patterns of deforestation,” says Daniel Romero-Álvarez, an epidemiologist at the SEK International University in Quito, Ecuador.

Brazil has stepped up surveillance, testing 10 percent of samples taken from patients with symptoms similar to Oropouche fever but negative for Zika, chikungunya and dengue. The Pan American Health Organization urged other states to do the same and provided training to diagnose the disease and analyze the virus. Although Oropouche fever has not resulted in deaths, suspected cases are being investigated.

As the number of infected people increases, so does the chance of discovering unexpected effects.” says virologist Felipe Naveca from Fiocruz, as happened with the Zika virus.

A neglected disease

Control of the disease is a challenge because the transmitting insect, Culicoides paraensis, is difficult to control and can easily penetrate mosquito nets. Removing waste and draining water reservoirs could help reduce the insect population.

C. paraensis is “a neglected vector for a neglected disease. No one bothered to study how to control it ”, says Joaquim Pinto Nunes Neto, entomologist at Evandro Chagas.

The insect has been found from the United States to northern Argentina, but not every place has the right conditions for Oropouche to spread. The future spread of the disease is uncertain, but estimates show that millions of people could be exposed.

Specifically, a model published in 2023 by Romero-Álvarez suggested that up to 5 million people across the Americas are at risk. But the number is likely an underestimate because the model did not predict the current spread of the disease to large cities such as Rio de Janeiro, and did not take into account future deforestation and climate change. It also did not consider the possibility that the common house mosquito (Culex quinquefasciatus)—and perhaps other insects—could transmit Oropouche, as some studies suggest.

The Oropouche virus could undergo genetic changes as it spreads, which could make it more dangerous. Having a genome consisting of three RNA segments, it can undergo genetic reassortment between different strains. Studies have shown that a variant emerged in Brazil in 2015 from the reassortment of virus lineages from Peru and Colombia. The impact of these changes on virus transmission requires further research.

We must… bring this virus out of the shadows“, concludes virologist Felipe Naveca.