This year is the second worst summer that our country has experienced since there were cases of outbreaks of the West Nile virus (WNV), which in 2020 claimed the lives of eight people. Five people have died in Spain in recent months from the infection, a situation that worries the inhabitants of the most affected areas, in Andalusia and Extremadura, who are demanding solutions.
What is West Nile Virus?
West Nile virus is a mosquito-borne zoonosis, the first case of which was detected in Uganda in 1937. Since then, infected people have been found in various parts of the world, including Europe, Africa, Asia, Australia, and North America.
The first cases in humans were detected in Spain in the early 2000s, but it was not until 2020 that its name began to gain prominence in our country, as the largest outbreak to date occurred, resulting in 76 infections in humans and eight deaths. This summer there was the second largest outbreak, with 38 cases and 5 deaths.
This virus, like Flavivirusis maintained through a mosquito-bird-mosquito transmission cycle, and bird migrations play a fundamental role in its expansion.
Why does this happen?
The WNV (West Nile virus) appears mainly in places where there are wetlands where birds and mosquitoes usually coexist. “In Spain, it has appeared mainly in cities located near rice-growing areas. Part of the problem is that when rice fields are flooded, if no control program is implemented, mosquitoes proliferate a lot and the insects move from the crops to the municipalities,” explains Jordi Figuerola, researcher and expert at the Doñana Biological Station. in mosquito-borne zoonoses.
This year, several factors that occurred at the same time have something to do with it, explains the researcher: “The first is that at the end of last year we detected the circulation of the virus until very late, well after the summer. At the beginning of November, we were still detecting the virus, whereas normally, by mid-October, it would already be there. missing, That is to say, its circulation intensity was so low that it became undetectable,” he explains.
This, combined with the high temperatures of last winter, which allowed mosquitoes to breed for longer and more females to survive the season; the rains in March and April, accompanied by temperatures well above 20 degrees, and the flooding of rice crops at the end of May, made for a perfect cocktail: “In other years, we detected it around June 17, and this year it happened earlier: June 4. After five weeks, human cases began to be diagnosed.
How dangerous is it?
In about 80% of infections, people have few or no symptoms. About 19% of people develop fever, headache, vomiting, or rash, and about 1% of people develop serious symptoms such as encephalitis, meningitis, stiff neck, confusion, seizures, or death. People most at risk for this disease are those over 60 years of age and/or those with health problems such as cancer, diabetes, or immunosuppression.
How does it spread and propagate?
It is usually spread during bird migrations. The cycle begins when a mosquito infects a bird, and then another mosquito bites the same bird. It is not a virus that is transmitted between humans. Mosquitoes usually infect humans and horses.
What can we do to contain it?
WNV is already endemic in our country, so we must learn to live with it. Experts say that its eradication is not realistic because it is almost impossible, so we must focus on containing it so that circulation is at low levels and, in this way, epidemics do not occur in humans like the one we are seeing.
“Whether there are more or fewer cases will depend on how we manage them. If we continue not to implement mosquito control programs in the rice fields and continue to plant rice up to the first street of the village, as is done in some municipalities, there will be (except in specific years) many cases,” says Figuerola.
On the other hand, he explains, outdoor places with stagnant water (such as fountains or abandoned swimming pools) should be avoided in environments very close to urban areas. He also insists that the plans already developed by the municipalities concerned must be renewed and evaluated periodically: “At the end of the season, municipalities must do a job of reevaluating their plans to see what changes they need to make to solve the problems.” that there may have been.
Regarding personal protection measures: eliminate possible places where there could be stagnant water in our house, install mosquito nets, use mosquito repellent and wear white clothes.
