The deaths of black birds indicate a threat of virus from the Western Imminent Nile in the United Kingdom

A fatal virus kills merles across the United Kingdom. Beyond the risk for birds, its propagation indicates that mosquito-transmitted viruses now represent a growing threat to humans and animals in the country, partly following climate change.

The virus in question, USUTU, is from South Africa in 1959 but is now widespread in Europe. It causes a deadly disease in certain species of birds, in particular Merles, and was detected for the first time in the United Kingdom in 2020. In some parts of the country, notably London, the populations of Blackbird have dropped by more than 40% since 2018. “We first noticed the decline at the same time as Usutu appeared,” says Hugh Hanmer At the British Trust for Ornithology.

Although devastating for the life of birds, the USUTU has a low risk for humans and mammals. Infections in people are rare and generally cause only a slight fever, but the arrival of the virus in the United Kingdom first marked the viral zoonosis transmitted by mosquitoes – a disease that can be transmitted from an animal to a human – had emerged in animals in the country. Virus experts are watching closely with the distribution of the disease, as it could be a model for the future spread of other diseases at the origin of mosquitoes.

For example, the Western Nile virus spreads in the same way as usutu and requires the same environmental conditions. “The same mosquitoes that can transmit USUTU can generally transmit Western Nile, and the same birds that act as hosts (for Usutu) can also act as Western Nile Hosts,” explains Arran madness to the British agency Animal and Plant Health (APHA).

Humans can also be infected with the Western Nile virus from a mosquito bite, but its symptoms can be more serious than those of the USUTU. About 20% of infected people will feel symptoms, including fever, headache, body pain, vomiting and diarrhea. In rare cases, the virus can cause serious inflammation of the brain and spinal cord, which can be fatal. There is no known human vaccine.

Climate change has contributed to accelerating the spread of the Western Nile virus through northern and east Europe, Research showsWhile the virus thrives in hot summer temperatures. In the Netherlands, USUTU was detected for the first time in 2016 and the Western Nile virus followed in 2020. British officials fear that a similar model is played out in their country, with studies demonstrating That the climate there is more and more welcoming for viruses transmitted by mosquitoes. “The idea is that, if we have used here, the Western Nile will probably arrive at a given moment and is likely to persist, given the good conditions,” explains Folly.

In response to the threat, APHA launched a project in 2023 to follow the ways of emergence and transmission of the USUTU and other viruses transmitted by mosquitoes in wild birds. This virus tracing infrastructure Will be vital if the country must respond quickly to the arrival of the Western Nile, explains Folly. “Our real objective, or our conduct from a government point of view, is to be able to detect these (new viruses) circulating in animal populations before obtaining a transmission to humans.”

Reina Sikkema At the Erasmus University Medical Center in Rotterdam studied the emergence of the Usutu and the Western Nile virus in the Netherlands. Although western Nile has not been detected since 2022, sHe thinks that the virus is circulating at a low level, currently held in check by the relatively cool climate of the country. “I believe it is present, but he needs the right circumstances to evade,” she says. British detection of the Western Nile is now almost inevitable, explains Sikkema, but she thinks that similar climatic factors could prevent the virus from spreading too much for the moment.

But the increase in summer temperatures, including Increase in the frequency of tropical nights -that the Metorological Agency of the Met Office of the United Kingdom defines as when the minimum temperatures do not fall below 20 ° C-could change the image in the United Kingdom, the Netherlands and other nations of northern Europe in the coming years, warns Sikkema. “The disease transmitted by mosquitoes is not (just) during your vacation in Spanish or when you go to the South Americas,” explains Folly.

In addition to the potential risk of the Western Nile virus for people, madness says we shouldI do not forget what USUTU does to the Blackbirds of the United Kingdom: “If 40% of humans died dead in London, you would know it quickly enough.”