We are going to discuss about West Nile Virus symptoms, prevention and treatment methods. This virus (WNV) is an infectious agent of the Flavivirus genus , which is also responsible for other diseases such as yellow fever, dengue, and Zika. It was discovered in the 40s of the last century, in the Ugandan West Nile basin, and was later identified in Egypt (1942) and India (1953), according to Manuel Peinado in The Conversation.
The time is affected by Corona virus (COVID 19), there are other viruses that are killing people. These are some keys to highlight of this pathogen that has generated an outbreak of cases in Andalusia this week.
What mosquito transmits this virus?
The head of Mosquito Alert Entomology and member of the Mosquito Control Service of the Baix Llobregat Regional Council, Roger Eritja , explains to SINC that the most common vectors of this virus in southern Spain are Culex perexiguus and Culex pipiens , the latter better known as the common mosquito and one of the enemies of human summer nights.
“[The common mosquito] is the main vector. It is in the rooms, it bites at night, it waits for people to go to sleep and they flutter, spoil their sleep and itch ”, this expert details, adding that in Spain there are a total of 62 autochthonous species of which many have the capacity to transmit the WNV. “But in Andalusia, the vectors are perexiguus and pipiens “, he clarifies.
Eritja warns that Aede japonicus or Japanese mosquito is being misidentified as responsible for these WNV cases. Although it is true that it can transmit the virus, this insect is not found in southern Spain, apart from the fact that in Andalusia “there are already enough species to transmit it without needing any exotic species.”
This species, identified by Mosquito Alert two years ago in Asturias, is mainly found in deciduous forests in cool humid mountain areas, “which makes little sense to find it in the south. It’s like thinking that there are giraffes in the Pyrenees ”, he exemplifies.
What diseases can WNV cause?
West Nile virus can infect humans, horses, and other mammals. According to the World Health Organization , the virus has no symptoms in 80% of infected people. The remaining 20% may develop West Nile fever , a disease characterized by fever, fatigue, headaches and body aches, nausea, vomiting, and to a lesser extent skin rashes on the trunk and enlarged lymph nodes. The incubation period usually lasts between three and 14 days.
In the most severe cases, which occur in one in every 150 infected people, a neuroinvasive disease can develop, such as West Nile encephalitis, meningitis, or polio. Symptoms of the latter are headaches, high fever, neck stiffness, stupor, disorientation, coma, tremors, seizures, muscle weakness, and paralysis.
Although these conditions can occur in people of any age, those over 50 and people with immunodeficiency are at higher risk.
How is Nile Virus transmitted to people?
WNV is a virus of birds, the main reservoirs and also victims of the diseases it causes, “with significant mortality and sometimes suddenly”, Eritja details.
Thus, vector mosquitoes acquire the virus by biting birds to later attack humans and to a lesser extent horses, thus completing the transmission. These birds, the expert adds, may be indigenous and carry the virus during their migration.
Can humans spread WNV?
The entomologist clarifies that the virus, once it reaches a person -or a horse-, encounters a dead end:” None of them is infectious, not even with a mosquito involved,” he emphasizes.
Therefore, a mosquito that bites a sick person will not acquire enough virus to transmit to another person who may later bite, while neither humans – nor horses – have the capacity to transmit the virus to each other.
What conditions are optimal for transmitting the West Nile virus?
Both mosquitoes and viruses are sensitive to environmental conditions , that is, to temperatures: “This type of event will occur in summer, even if there are mosquitoes in winter in some area,” says Eritja.
Thus, what WNV needs to be transmitted is: a large number of birds, that these carry a sufficient load of virus and a significant number of mosquitoes so that, by probability, they can be vectors of this virus to humans.
The researcher at the Doñana Biological Station (EBD-CSIC) and WNV specialist, Jordi Figuerola , pointed out in an interview with the EFE Agency that, during the months of confinement due to the coronavirus pandemic and thanks to the abundant spring rains in Andalusia, the populations of mosquitoes transmitting this virus have been able to increase in an unusual way.
Roger Eritja, in addition to seeing this hypothesis very favorably and giving “total credibility” to the Doñana expert, emphasizes that Mosquito Alert is observing what influence the decrease in human mobility has on the dispersal of mosquitoes, such as Aedes albopictus or mosquito Tiger.
On the other hand, he believes that during the months of confinement the breeding sites that people may have in their second residence – which was prohibited from going during the months of strong national isolation – would have been neglected, thus increasing mosquito populations in summer.
Prevention or treatment of West Nile Virus
Here are some ideas on West Nile Virus symptoms, prevention and treatment methods. The most effective method to fight the common mosquito is to limit its population before reaching its adult stage, which is when the insects have the ability to bite. “Since our service [Baix Llobregat Mosquito Control] appeared in 1983, a large-scale insecticide control has been carried out in the field with good results,” says this expert, adding that this is a task that is normally assigned to the local administration, despite being a problem that goes beyond the municipal scope.
If this is no longer possible, prevention involves protection with mosquito nets or repellants . The World Health Organization (WHO), for its part, adds to these recommendations the use of light-colored clothing, long-sleeved garments and trousers and avoid outdoor activities in the hours of most itchy mosquitoes, that is, the night.
Above the outbreak of cases of meningoencephalitis caused by the West Nile virus in Andalusia, various unknowns have arisen, in particular about the mosquito species involved. Culex perexiguus and Culex pipiens , native to Spain, are the main vectors of this virus, which resides in many birds and infects horses and humans. The Aedes japonicus , although it has capacity to transmit it , it is not in the south of Spain and appears to be responsible for the outbreak of this week.We tried to cover some West Nile Virus symptoms, prevention and treatment methods.