Fumigation has begun in southern Spain after a deadly virus was detected. Mosquitos carrying the West Nile Virus (WNV) were found in Benalup-Casas Viejas, in the Cadiz region. WNV belongs to the Flaviviridae family of viruses, along with dengue and yellow fever. The virus can be transmitted to humans via mosquitoes.
The incubation period ranges from two to 14 days, and up to 21 days in immunocompromised people. Those who do develop symptoms (most infections are asymptomatic) have a sudden onset of influenza-like illness (fever, headache, myalgia). Patients may also develop swollen lymph nodes and a rash on the neck, arms or legs.
One in 150 people will develop a disease that presents as meningitis, encephalitis or acute flaccid paralysis (sudden weakness) with high fever, neck stiffness, disorientation or confusion, severe muscle weakness, tremors, convulsions, paralysis and coma. The case fatality rate is highest in patients aged over 70 years old.
The Andalusian health department has put an alert area on the town for the next four weeks. No human cases have been reported so far, but last year, 158 people were infected in Spain, with 20 dying from complications.
The 2024 outbreak pushed local authorities to act sooner. Spraying programmes in ponds, wells and other stagnant water began in May and will continue until November. The aim is to kill off mosquito larvae before they mature.
Benalup is one of 16 towns in Cadiz now classified as high-risk, along with Jerez, Vejer, Tarifa, and Algeciras. All municipalities in Andalusia are required to have a mosquito control plan. There have been four cases of WNV in animals in Spain this year, none of which were in Cadiz.
The main advice for residents and tourists is to avoid mosquito bites by using repellents, wearing long sleeves at dusk and dawn, and fitting mosquito nets at home. People are also urged to remove stagnant water from gardens and patios, where the insects can breed.
Authorities say the only way to reduce the risk of another serious outbreak is to combine fumigation, surveillance, and citizen precautions.
The probability of a human outbreak of WNV in the UK is currently considered “at most, very low” by the Government. To date, no locally acquired human cases of WNV have been reported in the UK.
