New York Times, September 20, 2002
ederal health officials said yesterday that they were nearly certain the West Nile virus had been transmitted through blood transfusions, and that they were accelerating efforts to develop tests to detect the virus in blood.
To reduce the risk of transmission of the virus, blood banks are being advised to ask donors to call back if they develop a mild fever or flulike symptoms from West Nile fever in the days after they give blood. Blood centers would then consider withholding the blood of such donors so it would not be transfused, the officials said in a news conference.
The officials said that the chance of contracting the virus from transfusion was very low and that there was no chance at all of contracting it from donating.
Nevertheless, they said they feared that concern could threaten efforts to reduce the country's chronic blood shortage.
It is likely to be months before an effective blood screening test for West Nile is developed, the officials said. They suggested that patients in need of elective transfusions consider postponing a transfusion or surgery in which transfusions might be needed. Although the precise risk of transmitting West Nile virus cannot be calculated at present, it is very low, the officials said.
"The data look quite conclusive now that blood transfusion can, on occasion, be the source of West Nile," said Dr. William Schaffner, who is chairman of the department of preventive medicine at Vanderbilt University and who also works in the Tennessee health department.
The new evidence that the virus can apparently be transmitted through blood transfusions comes from the case of a 24-year-old woman in Mississippi who developed West Nile encephalitis. She received blood from 18 donors.
Scientists grew the virus from a sample routinely kept by blood banks from one of the donors, who sought medical care four days after donation because of fever, chills and a headache. That finding led to the new recommendation to blood banks.
The new findings place a burden on clinicians "to use blood only when the patient really needs it, and we should be critical about how much we use" as has been common medical practice in recent years, Dr. Schaffner said.
Patients facing elective surgery might consider donating their own blood in advance.
Precisely how long the West Nile virus can stay in a person's blood, and be a source of infection to a transfusion recipient, is not known. It is probably for only a few days after a mosquito bite, because the virus is difficult to detect in the blood once symptoms develop, said Dr. Jesse Goodman of the Food and Drug Administration.
The short time that the West Nile virus stays in the blood makes it far less likely to pose the kind of public health threat than did the viruses that cause AIDS and hepatitis B and C before tests were developed to screen them from the blood supply, Dr. Goodman has said.
The nation is experiencing its worst epidemic of West Nile fever since the virus was detected for the first time in this hemisphere in 1999 in New York City. As of yesterday, there had been 1,745 cases, including 84 deaths, from 36 states and the District of Columbia this year. The most deaths have occurred in Illinois, which said yesterday that a 23rd person had died from the virus. The death count by the Centers for Disease Control and Prevention does not include the latest death.
Also this week, a dog in Illinois died after being infected with the virus. But health officials said that the dog was not healthy to begin with and that household pets were considered at very low risk for the disease. Dogs are not known to transmit the virus to people.
Transmission of the virus has usually peaked from late August to mid-September. This year, the epidemic has probably peaked in the South, but scientists are not sure about the North, said Dr. Lyle Petersen, a West Nile expert with the disease control agency. The number of cases will continue to rise because of the time lag between diagnosis and sending information through the health system. "Any epidemic of this size is surprising; but it's not totally unexpected," Dr. Petersen said.
Because both the Mississippi woman and her blood donor live in areas where mosquito bites are transmitting West Nile virus, officials said they lacked scientific proof that transmission occurred through blood transfusion.
Still, "it is prudent to assume bloodborne transmission from transfusions can and probably has occurred," Dr. Goodman, the food and drug official, said.
Dr. Julie L. Gerberding, the director of the disease control agency, said in an interview that the new evidence was "pretty close to a smoking gun."
In addition to causing encephalitis and meningitis, West Nile infection can mimic the type of paralysis caused by polio, the officials said.
In the current epidemic of West Nile virus, doctors have mistaken West Nile's poliolike symptoms with those of a stroke or another neurological condition known as Guillain-Barre Syndrome, the officials said.
The officials reported six such cases, and said they were working to determine the frequency of the poliolike syndrome. The paralysis from West Nile is painless and usually does not involve loss of sensation. Its tendency to affect only one side of the body and the preservation of sensation distinguish West Nile paralysis from Guillain-Barre, which usually affects both sides of the body and usually involves changes in sensation.
Doctors were urged to perform tests to distinguish Guillain-Barre Syndrome or strokes from West Nile because treatments for those two conditions have risks and would be useless for those with West Nile fever. No specific treatment exists for West Nile fever beyond supportive care like good nursing and mechanical respirators when needed.
Dr. Jim Sejvar of the disease control agency said that the poliolike syndrome had continued with little improvement for one and a half to two months in patients in the current epidemic, but that doctors did not know how long it lasts.
The West Nile virus is closely related to one that causes St. Louis encephalitis. The pattern of the current West Nile epidemic resembles an epidemic of St. Louis encephalitis with nearly 2,000 cases in 1975, Dr. Petersen said.
"Even some of the same neighborhoods affected in 1975 are being affected with West Nile virus," Dr. Petersen said.
The overwhelming majority of West Nile cases have occurred among people bitten by infected mosquitoes. But recent reports of cases among recipients of organ transplants and blood transfusions raised concern about transmitting the virus through these probable new routes.
The disease control agency has previously reported that all four recipients of organs from one donor in Georgia developed West Nile encephalitis or illness. The agency is now investigating possible transmission of the West Nile virus in at least one other organ transplant recipient.
Additional evidence that West Nile virus can be transmitted through transplants came yesterday from scientists at the New York state health department who tested organs and tissues from a patient who died of the infection. Dr. Dale L. Morse and Dr. Guthrie S. Birkhead of the health department said that their team had detected West Nile virus throughout the patient's body, including virtually every organ that can be transplanted. The patient's organs were not transplanted.