Has West Nile Made It Cross-Country?
A Los Angeles County woman has tested positive for West Nile virus in what is believed to be the first case of a person contracting the illness in the western United States, health officials said Friday in announcing preliminary laboratory results.
The results of further tests won't be known for another week, but county health officials called it a probable case of locally acquired West Nile virus infection.
The diagnosis in Los Angeles surprised health officials because ongoing monitoring of chicken flocks, dead wild birds and mosquitoes had shown no trace of the virus in California.
"The virus' arrival in California is anticipated, but unexpected at this time since it is not present in any contiguous states," said Dr. Thomas Garthwaite, director and chief medical officer of the Los Angeles County Department of Health Services.
Since West Nile was first detected in New York in 1999, the virus has been found in humans in 27 other states and the District of Columbia.
In addition, Boston health officials confirmed the first human case of West Nile in a resident of that city and Louisiana health officials said they confirmed that an 83-year-old woman had died from the virus.
Nationwide this year, there have been 854 confirmed human cases of the virus, including 43 deaths, according to the U.S. Centers for Disease Control and Prevention.
"California now joins the list," said Dr. Diana Bonta, the state's health director.
The woman had not traveled outside the region for several months, county Department of Health Services spokeswoman Maria Iacobo said.
"It is rare to find a human case before a case in birds or mosquitoes, but it is not impossible," said Dr. Jonathan Fielding, Los Angeles County's public health director. He said the assumption is that the woman, who also did not have a — blood transfusion, contracted the virus from a mosquito, but the actual cause remains unknown.
Local health officials said she lived in southwestern Los Angeles County but would not identify her or give her age. They described her only as a young woman.
She became ill with viral meningitis Aug. 10 and was hospitalized Aug. 12. Since then, she has fully recovered and resumed her normal activities, according to the California Department of Health.
While its push westward had been expected, until Friday there had been no confirmed cases of humans contracting the disease west of the Rocky Mountains.
In the four other western cases of confirmed West Nile virus, the victims are thought to have been infected in states where the mosquito-borne virus is already known to be present.
Los Angeles County officials have tested six people, including the one woman thought infected, for the virus. Two of those tests have come back negative, with results pending for the three others.
West Nile virus is closely related to St. Louis encephalitis, already present in California and other western states. It typically causes flulike illness or no symptoms at all in humans. In about one in 150 cases, it can lead to illness including deadly inflammation of the brain. The young and the elderly are especially at risk.
Officials estimate there could be 110,000 to 150,000 people who have been infected in the United States, most of whom will never suffer its effects or know they have the virus.
On Thursday, U.S. health officials said a fourth person who became ill after receiving a donated organ from a Georgia car crash victim tested positive for the virus, strongly suggesting the disease can be transmitted by means other than a mosquito.
The CDC said it was still trying to determine whether the organ donor, whose organs also went to three other people who tested positive for West Nile, became infected through a mosquito bite or blood transfusions before organ donation.