West Nile Probably Transmitted Through Blood

ATLANTA (Reuters) - The potentially fatal West Nile virus can survive in some blood products and probably be transmitted from person to person through transfusions, US health experts said on Thursday.

In a weekly update, the US Centers for Disease Control and Prevention revealed that the virus had been found in a unit of fresh frozen plasma given to a 24-year-old Mississippi woman who suffered postpartum bleeding in July.

The woman later tested positive for the mosquito-borne disease.

"The isolation of live West Nile virus from a blood product indicates that the virus can survive in some blood components and probably can be transmitted by transfusion," Dr. Lyle Petersen, a CDC West Nile expert, said in a conference call.

Petersen, however, added that authorities could not be certain the transfusions were the source of the woman's infection because she lived in an area where the mosquitoes that usually spread the disease were active.

There have been 1,641 human cases of West Nile in the United States this summer, including 80 deaths, according to the CDC. The outbreak is the largest since the virus struck the United States three years ago.

Fears that West Nile, which can cause the severe brain inflammation encephalitis, could be transmitted through organ transplants and blood transfusions surfaced earlier this month after four organ recipients were reported to be infected.

Including the case of the 24-year-old Mississippi woman, the CDC is investigating about half a dozen people who may have received blood from products contaminated with the virus.

OTHER WEST NILE VICTIMS

The Atlanta-based agency also said it was aware of six other West Nile victims in Mississippi and Louisiana who had developed weakness and a polio-like paralysis in their extremities.

Although most people who acquire West Nile have no symptoms and those who do normally suffer little more than flu-like illness, it is believed they can still carry small amounts of the virus in their blood for several days.

Up to 200,000 Americans may have been exposed to West Nile since 1999, when it killed seven people in the New York borough of Queens. An estimated 4.5 million Americans receive blood or blood products annually.

There is currently no way to screen blood for West Nile, though the Food and Drug Administration said it was working with blood banks and laboratories to develop a test.

"What we're trying to do is jump-start and facilitate this process so that we can get a test available as soon as possible," said Dr. Jesse Goodman, deputy director of the FDA's Center for Biologics, Evaluation and Research.

Goodman, however, noted that the benefits of receiving blood outweighed the potential risk of becoming infected with the virus.

While federal agencies grapple with that issue, state and local health officials continue to battle the virus, which has entered its traditional peak period.

Although initially centered in the southern states of Louisiana, Mississippi and Texas, this year's outbreak has moved into the Midwest with a vengeance. States such as Illinois and Ohio have been particularly hard hit.

Illinois on Thursday reported another death from the virus, bringing the number of fatalities there to 23, more than twice that of any other state. Illinois has recorded 457 confirmed human infections, also the most in the nation. Ohio has 169 cases, Michigan 166.

At least 36 states and the District of Columbia have reported human cases of West Nile this year.