Two Stanislaus County women infected with the West Nile virus are the first confirmed human cases in California this year, local and state health officials said Friday.
The state Department of Public Health said Friday that the women were identified after donating blood. A routine screening by the blood bank discovered the illness.
Both women developed symptoms, but they are recovering without hospitalization.
Last month, two dead birds found in west Ceres were reported to the state's West Nile virus hot line and tested positive for the mosquito-borne illness, Stanislaus County officials said.
"West Nile virus, unfortunately, is here to stay," said Dr. John Walker, public health officer for Stanislaus County. "It's not like our whooping cough epidemic, where it comes and goes. (West Nile virus) is within our bird population, and it's going to cycle probably every year."
He said 14 people are known to have been stricken with the virus last year in Stanislaus County. In 2008, 18 people in the county were infected. The virus first surfaced in the county in 2004.
A third positive blood donor was reported in Madera County. The individual has not developed symptoms so it is not considered a case of West Nile virus.
Last week, officials reported that they found West Nile virus in southern San Joaquin County in positive tests of mosquitoes. The virus was detected in the Division Road area southeast of Tracy and south of Manteca, according to the San Joaquin County Mosquito and Vector Control District.
Mosquito bites are the most common route of West Nile virus infection. Health officials warn people to drain areas of standing water when possible and take precautions to avoid mosquito bites.
"It's very important for people to protect themselves, especially at dusk and at dawn," Walker said. "With the Stanislaus County Fair starting, people should put on insect repellent every evening and every night."
The two Stanislaus County cases put 2010 ahead of the pace from last year, when there were zero human cases through July 15, state officials said.
Overall, there were 112 cases in the state last year, including four that turned fatal. The 2009 case total was well off the 2008 mark of 445.
Heading into this week, there were 10 human cases nationwide, with Colorado (three) and Georgia (three) setting the pace. Arizona, Mississippi, North Dakota and South Dakota each reported one case through July 13.
To date, the virus has been detected in 19 California counties in 52 dead birds; 107 mosquito samples; six sentinel chickens, which are used in rural parts to detect West Nile virus and other mosquito-borne diseases; and one squirrel, state officials said.
"With the first confirmed human illnesses from West Nile virus this year, we are intensifying our surveillance for the virus with the help of all counties," said state Department of Public Health Director Dr. Mark Horton in a news release. "The most important step people can take to prevent West Nile virus infection is to protect themselves from being bitten by a mosquito."
Bee staff writer Rosalio Ahumada can be reached at firstname.lastname@example.org or 578-2394.