After the first two cases of West Nile virus in Yolo County this year were confirmed last week, Davis residents should take all precautions against mosquitoes – especially considering recent high temperatures.
An older man between the ages of 55 and 74 and a younger boy between 10 and 18 years old, both from Davis, were the first human cases of West Nile in Yolo County.
Exact ages of the males were not given to protect their identity, though the geography of where the virus is contracted is important for public health, said Dr. Joseph Iser, Yolo County health officer and director.
The older male had a more severe case of the virus, but both men are recovering.
Eighty percent of infected people do not show symptoms of West Nile, but for the remaining 20 percent, symptoms usually show three to 10 days after the infected mosquito bite. These include high fevers, headaches, body aches, nausea, vomiting and rashes. One in 150 people who do show symptoms show severe symptoms, like the older Davis resident.
A few cases each year are common and Yolo County has had a lower number of West Nile cases this year – so far, Iser said.
“[Yolo] is way below numbers we had at this time last year,” Iser said. “But we should still use this as an opportunity to teach people about mosquito control.“
Dr. Vicki Kramer, chief of the vector borne disease section of the California Department of Public Health, which oversees the California West Nile virus surveillance information center, said 52 human cases of West Nile have been confirmed in California so far. Two fatalities have been reported.
“In Yolo County, the level of activity is not unusually high,” Kramer said.
In past years, California’s numbers of human cases have ranged from 250 a year to over 800.
Kramer said the decrease in cases for 2009 in California, and even nationwide, may be due to cooler temperatures, better mosquito control in urban areas and higher immunity of birds, who are carriers of the virus.
Though mostly reported in humans, West Nile is also found in animals such as in horses and squirrels.
A first sign of West Nile in an area is an increase of dead birds. Kramer said to help with local surveillance residents should report dead birds to the California health department’s West Nile Web site, westnile.ca.gov.
West Nile virus is transmitted from infected birds to mosquitoes, then from mosquitoes to humans and other animals.
New in the U.S., the first strains of West Nile were found in New York in 1999 and slowly moved westward to California, arriving by 2003.
Sacramento and Yolo mosquito vector control district public information officer Luz Maria Rodriguez also said a few cases in this region are common, yet each case should still serve as a warning for residents.
“Cases serve as a wake up call and reminder that people need to be careful and take precautions against mosquitoes,” Rodriguez said.
Basic measures to reduce contact with mosquitoes are to watch and monitor any standing water, avoid outdoor activity at high mosquito activity times including dawn and dusk, wear insect repellent and cover skin with long pants and sleeves when mosquitoes are active.
Though winter and fall see different species of mosquito that are non-carriers of West Nile, unusually high temperatures this week make for perfect mosquito conditions.
Mosquitoes need water to exist. Add heat and mosquitoes life cycle from egg to adult accelerates, increasing mosquito populations in the region.
“Just because cases are down this year doesn’t decrease the seriousness of the disease,” Rodriguez said.
Visit fightthebite.net to get free mosquito repellent for outdoor evening events and more West Nile information to help prevent cases of West Nile.
SASHA LEKACH can be reached at firstname.lastname@example.org.