The West Nile virus keeps health surveillance activated in several autonomous communities. Andalucía has confirmed 47 cases during 2026, including 15 neuroinvasive cases and one death, according to the latest report from the Junta de Andalucía, updated this Wednesday, August 19.
The balance includes a new infection in Dos Hermanas, in Seville. Of the diagnosed patients, 32 have presented mild symptoms and seven remain hospitalized.
In Extremadura, the Extremadura Health Service has confirmed 17 infections so far this year, with six people hospitalized. Given the increase in diagnoses, knowing how the disease is transmitted and what its symptoms are is essential to identify risk situations.
What is the West Nile virus
The West Nile virus is a pathogen of the flavivirus genus that can cause the so-called West Nile fever. It is a zoonosis: a disease that circulates among animals and that, under certain circumstances, can affect humans.
Its natural cycle occurs mainly among birds and mosquitoes. Birds act as a reservoir for the virus, while insects can acquire it by biting them and subsequently transmit it.
According to the World Health Organization, the virus was first identified in Uganda in 1937. It currently circulates in various regions of Africa, Europe, America, and Asia.
Which mosquito transmits the disease
The main route of transmission is the bite of an infected mosquito of the Culex genus, common in numerous urban and rural environments.
The insect contracts the virus by feeding on an infected bird. If it then bites a person, it can transmit the infection. Other mammals, especially horses, can also be affected.
However, an infected person does not transmit it to another through human contact. There are exceptional routes, such as blood transfusions, transplants, or transmission during pregnancy. Therefore, health authorities apply specific controls when they detect circulation of the virus.
What impact does the mosquito have in Spain and Europe
The impact varies considerably depending on age, health status, and the circulation of the transmitting mosquitoes.
In Andalucía, the official report from August 19 records 47 confirmed cases, 15 neuroinvasive forms, one death, and 28 municipalities declared alert areas.
In Extremadura, the Junta has reported 17 infections in 2026. The previous year, this community reported 39 cases and five deaths.
On a European scale, the European Centre for Disease Prevention and Control counted, up to August 13, 429 human cases in nine countries, including Spain.
These figures correspond to detected cases. As many infections do not produce symptoms, the actual number of infected people may be higher.
What are the symptoms of the West Nile virus
About 80% of infected people do not develop symptoms. Approximately 20% present a generally mild illness, similar to a flu-like process.
The most common symptoms are:
- Fever.
- Headache.
- Tiredness or weakness.
- Muscle and joint pain.
- Nausea, vomiting, or diarrhea.
- Skin rashes.
- Swelling of the lymph nodes.
The clinical guide from the Ministry of Health indicates that the usual incubation period is between two and 14 days after the bite, although it may be prolonged in immunocompromised individuals.
Most affected individuals recover, but fatigue may persist for weeks.
Is there any treatment?
Currently, there is no authorized vaccine to prevent the disease in humans nor a specific antiviral treatment with proven efficacy.
In mild cases, care usually focuses on relieving symptoms through rest, hydration, and medications to control fever or pain when indicated by a healthcare professional.
The Ministry of Health indicates paracetamol as an option to reduce fever, always respecting medical indications and particular contraindications. Antibiotics do not eliminate the virus and should not be taken without a prescription.
When neurological complications arise, hospitalization, administration of intravenous fluids, medical monitoring, and, in the most severe cases, respiratory support may be necessary.
How to act in the face of the first symptoms
If fever, headache, or malaise appears after being in an area with virus circulation, it is advisable to contact the health center and inform about possible bites and places visited.
Older individuals, immunocompromised people, or those with chronic diseases should consult quickly.
If neck stiffness, confusion, difficulty speaking, muscle weakness, seizures, or alterations in consciousness occur, it is necessary to go immediately to the emergency room or call 112.
The diagnosis corresponds to healthcare professionals, who can request blood tests and, when there is suspicion of neurological involvement, additional tests. Having received an isolated sting does not necessarily mean that the disease has been contracted.