West Nile Virus (WNV), a potentially fatal illness trasmitted by mosquito is biting deeper into the US state of California. Late last week, Governor Arnold Schwarzenegger declared a state of emergency in three of the state’s counties: Kern, Colusa and San Joaquin. WNV has killed four people in the state so far this year and the spread shows no sign of abating. The emergency declaration comes with a 1.35 million dollar fund.
WNV appears to be hitting California much harder this year than last, and Kern County most of all. Over 60 per cent of the state’s 64 cases of WNV have been reported in the county, including two elderly residents who died last month.
The most recent deaths in California were two elderly residents in Colusa and San Joaquin. Meanwhile in the county of Santa Clara, they have reported their first case of human WNV infection this year.
“The important thing is that we all go all out and we work together, the counties and the state, in order to get the job done and get rid of the virus,” said Schwarzenegger when he met with mosquito control officials late last week according an Associated Press report.
California State Senator Dean Florez, D-Shafter, said in a statement last week that he wants to see funding in next year’s budget so that a more proactive approach can be taken to monitoring and controlling the WNV mosquito.
WNV activity is monitored by counting cases in animals and birds as well as in humans. The number of counties in California affected this year is 42, compared with 43 in the whole of last year, and the high season is still to come (August and September). And the number of human cases last year was only 20 compared with over triple that number so far this year (64), according to statistics from the California State Department of Public Health (CDPH).
The number of dead birds infected with WNV recorded in California so far this year is 502 compared with 299 last year, and the number of mosquito samples with WNV this year is 402 compared with 349 last year.
Mosquitoes that have fed on infected birds spread WNV to humans and animals through bites. WNV originates from Africa, Asia and the Middle East but is now common in North America.
WNV cannot be spread from touching or being intimate with an infected person, and transmission via blood transfusion is extremely rare because all donated blood in the US is now tested for WNV.
Fortunately, the vast majority of people infected with WNV (about 80 per cent) experience no symptoms at all, which makes it very difficult to track.
People who do experience symptoms usually show signs between 3 and 14 days after being bitten by a WNV carrying mosquito.
Fewer than one per cent of people infected with WNV become seriously ill with symptoms such as high fever, headache, stiffness in the neck, feeling disoriented, apathy, convulsions, tremors, feeling weak in the muscles, loss of vision, feeling numb, and less commonly, paralysis and coma. The symptoms last several weeks and may lead to permanent damage of the brain and nervous system. The over 50s are more at risk of serious illness than younger people.
About 1 in 5 people with WNV have mild symptoms. These include fever, headache, body aches (like the flu), feeling sick, vomiting, and sometimes swollen glands, skin rash on the chest, stomach and/or back. These milder symptoms last for a few days, but it is not unknown for healthy people to go on to develop more serious symptoms.
Being outside at dawn and dusk increases a person’s chances of being bitten by a WNV carrying mosquito because this is when they are flying around.
Precautions include making sure you wear long sleeves and pants at these times, cover exposed skin with a recommended mosquito repellent, fasten your door and window screens securely and repair any rips or tears.
Also, make sure your back yard or garden has nowhere suitable for breeding mosquitoes such as still water left standing after rainfall: check flower pots, ponds, water butts, wells. Mosquitoes don’t settle in running water to breed, they like still water that is warm and stagnant.
Written by: Catharine Paddock