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The West Nile virus, transmitted by mosquito bites, has caused the outbreak of viral meningoencephalitis in Seville that has infected 19 people, 17 of them admitted to hospitals and seven to the ICU. Laboratory analyzes of 12 patients from Coria del Río and La Puebla del Río, riverine towns of the Guadalquivir with a large presence of mosquitoes, have tested positive for this virus, as confirmed by the Andalusian Board on Thursday.
After the recommendations for the 42,000 residents to stop mosquito bites with the use of repellants, avoiding walks at sunrise and sunset, installing mosquito nets or wearing long sleeves, now the Ministry of Health has activated the established protocol, which includes spraying . "We will have measures to fight the mosquito in addition to preventive measures, measures to eliminate them as soon as possible," advanced the Andalusian Minister of Health, Jesús Aguirre.
The virus, transmitted by the mosquito of the genus Culex, a common mosquito in our environment, causes 0.1% of deaths among those infected, 1% of inflammation in the meninges and the brain [meningoencephalitis], and 20% of fever controllable and 80% asymptomatic cases, according to the World Health Organization (WHO). The samples analyzed at the Andalusian Virology Center have been sent to the National Microbiology Center for counter-analysis.
How is its expansion slowed? “It is very complicated because the most important vector is our common mosquito. That handful of infected people who have become ill in Seville means that there will be many infected, about 2,000 [humans are not transmitters of the virus, only birds] ", calculates Joan Ramón Villalbí, member of the board of directors of the Spanish Society of Public Health and Health Administration (Sespas). Villalbí recalls that “aggressive chemical media” should be discarded due to their harmful effects [such as the fumigation carried out in New York in 2000 and 2012] and urges to control mosquito breeding areas and take extreme preventive measures.
However, Jordi Figuerola, a researcher at the Doñana Biological Station who has studied the transmission of the Nile virus since 2003, warns that with the summer already advanced and a presence of mosquitoes 30% higher than that registered in 2019, fumigation is the only solution, in addition to the fact that there are products with minimal damage to the environment in the surroundings of Doñana. “There are substances that used correctly should not cause problems. At this point it is necessary to propose actions to reduce the population of adult mosquitoes, treatments with pesticides. The ideal is to kill the larvae, but since we already have what we have, we must try to drop the transmission. Fumigating is not a panacea, but it does have an effect ”, explains this expert in field ecology and the dynamics of infectious disease transmission through mosquitoes.
Figuerola points to the confinement caused by the pandemic and the abundant spring rains as the cause of the unusual increase in mosquitoes in the Coria del Río and La Puebla del Río areas, 30% more than in 2019. “The population was not in the field, This has caused water to accumulate in many places where it would not accumulate or it would drain very quickly, which has generated mosquito breeding sites ”.