“Sloth Fever” Virus Spreads: What You Need to Know About Oropouche

“Sloth Fever” Virus Spreads: What You Need to Know About Oropouche

Mariana Lenharo & Nature News

The mysterious insect-borne virus that causes Oropouche fever, once confined to the Amazon region, has been expanding its range since late 2023, raising international concern. More than 8,000 cases have been confirmed in the Americas so far this year, most in Brazil, but also in Peru, Bolivia, Colombia and Cuba.

Brazilian authorities reported in July that two adults had died from the disease, the first deaths since the virus was identified nearly 70 years ago. Brazilian authorities are also investigating fetal deaths and birth defects that may be caused by the virus. Research has found that the virus can be transmitted from pregnant women to their fetuses. There is no vaccine or treatment for the disease.

Earlier this month, the Pan American Health Organization raised the risk level for Oropouche from medium to high, citing the geographic spread of the virus and the occurrence of fatal cases, which is remarkable for a disease that has historically been known to cause mild to moderate symptoms. On August 23, the World Health Organization issued a memo stating that the public health risk from the virus is high at the regional level but low at the global level. The U.S. Centers for Disease Control and Prevention has recommended close monitoring of people returning from affected areas. Cases of Oropouche infection have been confirmed in people who traveled from Brazil and Cuba to the United States, Spain, Italy, and Germany, including 20 cases of travelers from Cuba to the United States reported by the CDC on August 27.

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Nature We spoke with Gonçalo Bello, a public health expert at the Oswaldo Cruz Institute in Rio de Janeiro, Brazil, who is studying the lineage of Oropouche virus currently circulating in the Americas.

What is Oropoush?

Oropouche is a virus of the genus. OrthobunyavirusUnlike better-known vector-borne viruses such as dengue, Zika, yellow fever and chikungunya, it is usually transmitted to humans by midges. BitingHowever, it cannot be ruled out that other vectors may be involved, rather than mosquitoes. (The virus has also been found in other insects, including mosquitoes.) Ieca.

How long has this virus been around?

The virus was discovered in the Caribbean in Trinidad and Tobago in 1955. It was first detected in blood samples from sloths in Brazil in 1960. Since the 1960s, it has been more or less intermittently found in humans in the Amazon region (a vast area spanning nine South American countries). This is why it is called a re-emerging virus, because it has been circulating in the Amazon, where it is considered endemic, for at least decades.

Why are we hearing about this now? Is this the biggest outbreak yet?

As for the Amazon region, it is difficult to say whether the current epidemic is larger than in previous decades, as for the first time a molecular surveillance and diagnostic system has been introduced that did not exist during previous epidemics.

The geographical spread of the infection marks a change: the number of affected municipalities and states is now much higher. In addition, the virus has spread outside the Amazon region. Again, no surveillance of Oropouche has been carried out outside the Amazon until now, so we do not know if this is the first time.

There are also concerns that Cuba has confirmed its first locally transmitted infections, and that imported cases have been reported in Europe and the United States. Biting Chironomids are found throughout the Americas, from the United States to Argentina, and local transmission can occur when there is an infected person and a vector, meaning that an infected individual can cause a local outbreak, which is the main concern.

What are the symptoms?

Symptoms are similar to those of other arboviruses such as dengue fever, including fever, headache, muscle and joint pain, pain behind the eyes, vomiting, and nausea. Therefore, diagnosing Oropauche infection based on symptoms alone is very difficult and requires molecular diagnostic testing. In a small number of cases, the disease progresses to a more severe illness with neurological and hemorrhagic symptoms. However, most cases are mild and resolve within 7-8 days.

Is the virus getting more dangerous and could it cause microcephaly, an abnormally small head in babies?

For the first time, antibodies against Oropouche, indicative of recent infection, were found in newborns with microcephaly, suggesting an association, although limitations of the study meant that a causal relationship between intrauterine infection and neurological malformations could not be established.

However, in cases of fetal and neonatal deaths, it has been possible to establish evidence of mother-to-child transmission. In one case, a pregnant woman showed symptoms of Oropouche and the fetus died a few weeks later. Oropouche genomes were detected in several organs of the fetus. In another recent case, a pregnant woman tested positive for Oropouche. The baby was born but died a few weeks later. Postmortem examination identified viral genomes in various tissues, including the brain.

Two previously healthy young women, who were not pregnant, also died after developing severe dengue-like symptoms. These are the first documented cases classified as deaths associated with Oropouche infection.

It is not yet possible to determine how frequently these fatal cases occur, either in adults or in fetuses, and so far there is no evidence that symptoms have changed compared to previous outbreaks.

This article is reprinted with permission. First Edition August 26, 2024.