West Nile virus-infected mosquitoes have been found in a section of Sunnyvale, California, prompting Santa Clara County officials to schedule an overnight control treatment on Friday, September 25.
The operation is due to begin at about 10pm in a limited area of the city’s 94089 postcode. Officials have not disclosed how many infected mosquitoes were identified.
Sunnyvale mosquito treatment
Santa Clara County Mosquito and Vector Control will use Zenivex, an insecticide approved for use by the US and California environmental protection authorities.
The treatment will be carried out using truck-mounted equipment that releases an ultra-low-volume mist designed to kill flying adult mosquitoes on contact. Similar operations normally begin at around 10pm and finish by about 2am.
Residents do not need to leave their homes. Those wishing to reduce their exposure can close windows and remain indoors while the treatment is taking place, although county guidance says the pesticide is applied in very small quantities and breaks down after exposure to sunlight.
Officials say adult mosquito treatments are conducted when West Nile virus is detected and are intended to reduce the number of infected insects capable of biting people. They must be organised quickly because delaying treatment could increase the risk of human infection.
West Nile virus symptoms and precautions
West Nile virus is most commonly spread by the bite of an infected mosquito. Many people experience no symptoms, while others may develop fever, headache, body aches, nausea, vomiting or a rash.
In more serious cases, the infection can affect the nervous system and lead to hospitalisation or death. There is currently no vaccine or specific medicine available to prevent or treat West Nile virus in people.
Health officials advise residents to use an insect repellent approved by the US Environmental Protection Agency, wear loose-fitting clothing that covers the skin and avoid being outdoors around dusk and dawn, when mosquitoes are most active.
People can also help limit mosquito numbers by removing standing water from items such as plant pots, buckets, bins, old tyres and other containers around their homes.
