Since the end of the 20th century, it has continued to spread around the globe, to the point where it is now one of the main diseases carried by mosquitoes. This Thursday, August 8, the health authorities of Guadeloupe revealed that a first human case of infection by the West Nile virus had been detected on the archipelago.
According to Guadeloupe the 1stthe infected individual is a man who was “staying” in the overseas department. As the public service media specifies, the patient “is currently being treated in hospital”. While the local regional health agency (ARS) has stated that it is monitoring the situation closely, what are the characteristics of the West Nile virus and what risks does it present?
As indicated Public Health Francethe West Nile virus is transmitted to humans by mosquitoes, but it originally comes from different species of birds. “The mosquito becomes infected by feeding on infected birds,” describes the government website. “The infected mosquito can, during another bite, transmit the virus to another bird or to an accidental host such as a man or a horse.”
These two species of mammals are those that fix the virus most easily, but according to Santé Publique France, they “represent ‘epidemiological dead ends’ for the West Nile Virus because the quantity of virus in the blood (viremia) is insufficient to infect the mosquito during a bite and thus allow the transmission of the disease”.
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In short, transmission occurs mainly from birds to mosquitoes, then from mosquitoes to humans or horses. However, it is impossible for an uncontaminated mosquito to pick up the virus by biting a human or a horse.
According to Public Health France, transmission can also occasionally occur through “products of human origin: blood transfusions and organ, tissue or cell transplantations. Cases of transmission from mother to child during pregnancy, childbirth and breastfeeding have also been described.”
According to a file from the Pasteur Institutethis virus “takes its name from the West Nile district of Uganda, where it was first isolated in 1937 from a woman suffering from a high fever. It was subsequently detected in humans, birds and mosquitoes in Egypt in the early 1950s, and has since been found in humans and animals in many countries.”
The West Nile virus is now endemic in several African and European countries, but cases have also recently been observed on the American continent or in Western Asia. According to the ARS of Guadeloupe, it is now considered the second most widespread flavivirus (virus transmitted by an arthropod) in the world, after dengue fever, but ahead of zika and chikungunya.
According to the Pasteur Institute, the West Nile virus is fortunately asymptomatic in about 80% of cases. In the remaining 20%, the symptomatic form manifests itself, at the end of the incubation period (which can last from 2 to 6 days, sometimes longer), by “the sudden onset of a high fever”, which can be “accompanied by headaches and backaches, muscle pain, a cough, swelling of the neck glands, and often a rash, nausea, abdominal pain, diarrhea and respiratory symptoms”.
As Public Health France indicates, in some rare cases, the symptoms can even be more severe: “Serious forms of the disease occur in less than 1 in 100 infected people, mostly adults and especially the elderly. These are neuro-invasive forms manifesting as meningitis, meningoencephalitis, flaccid paralysis or Guillain Barré syndrome (a disease of the peripheral nervous system, editor’s note).”
“These neuroinvasive forms are more common in older people and can cause after-effects and even be fatal in humans,” the government website continues. The Pasteur Institute reports that a count carried out in 2012 in the United States revealed a proportion of 183 deaths out of the 4,500 cases of infected (and therefore symptomatic) people diagnosed on American territory.
One of the main problems with the West Nile virus is that there is currently no specific treatment to combat the micro-organism. While there is a vaccine, it is only suitable for horses. In humans, it is therefore not possible to protect against the virus… and there is no antiviral treatment after infection either!
As explained by Santé Publique France, “the care (of infected people) is therefore focused on treating symptoms when they are present. Serious cases are treated in a hospital setting, in intensive care if necessary.”
Thus, the best way to preventatively fight against this virus seems to be to directly fight against mosquitoes, to keep them away and to protect oneself from their bites. Public Health and the Pasteur Institute also insist on the fact that in particularly infested areas, protective measures must be both “individual and collective”.
