When West Nile virus begins sickening and even killing vulnerable California residents this summer, doctors expect that worried patients will pressure them for a definitive diagnosis.
But getting tested for the mosquito-borne illness will not be as simple as some may think.
Only the sickest patients with specific symptoms should be tested, according to guidelines promulgated by federal and state health officials.
That means that potentially thousands of people will become infected and not know it.
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Symptoms can range from flulike fever and body aches to convulsions, stupor and vision loss. Yet only 20 percent of those infected will experience any symptoms at all, and only 1 percent of those will be diagnosed with a serious consequence of the disease such as meningitis or permanent paralysis.
Complicating the medical response: Doctors can't offer any treatment, except in the hospital, where gravely ill patients may get intravenous fluids and other supportive care.
If physicians follow the state and federal guidelines for confirming a suspected case of West Nile virus, they will submit blood samples to a lab for analysis only if a patient has meningitis, encephalitis, acute flaccid paralysis or other serious neurological problems or has had a high fever for a week or more.
"We didn't want to have everyone tested under the sun who didn't have symptoms," explained Dr. Carol Glaser, chief of the viral disease laboratory at the state Department of Health Services. "There are a lot of different viruses that circulate both winter and summer that could give you a nonspecific viral illness for a couple of days. With West Nile they tend to be sicker."
Dr. Thomas McKnight, a Chico neurologist who took care of several West Nile victims last year, said most people will not become truly sick with the illness.
"They just may have some fever, body aches and even a headache," he said. "They can expect tiredness, reduced appetite and sometimes nausea and diarrhea, which is gone in five to seven days. If they had a history of suspicious exposure (to West Nile) we would test them, but I don't think most doctors would test their patients if they have a mild viral illness."
Glaser added that in cases in which the patient has not developed a neuroinvasive disease, the test may not detect antibodies to the virus, which would indicate exposure. The antibodies are gone within five days.
"So we thought that if someone has been ill for a week, the chances of detecting it are higher than if you tested on day 2 or 3."
As a result, most of those with mild West Nile symptoms will not be tested. Last year, for example, the state logged 830 human cases of West Nile virus, but state officials estimate that as many as 4,500 were infected. Glaser said officials arrived at the 4,500 figure by multiplying the number of neuroinvasive cases - 300 - by 15 because for every one neuroinvasive case, there are 15 of West Nile fever.
"People aren't sick enough to go to the doctor, or they don't get tested, or we don't capture every single lab test," she said.
Ray Palmer, of Fair Oaks, may have been one such case. The retired corporate developer was swarmed by mosquitoes in Utah in September and drove home with 30 or 40 mosquito bites.
About a week later, the normally fit 68-year-old said he felt so achy he couldn't lift his coffee cup. The illness lingered, and a trip to his doctor in February resulted in several blood tests but no definitive diagnosis. He said he never was tested for West Nile virus.
"It's the only thing they didn't test for, so what do you do?" he asked.
While many cases will continue to be missed, Glaser said, the state does want doctors to test highly suspicious cases and to report them.
Knowing who is getting infected and in what part of the state is important for tracking the disease, she said. Perhaps more important, she said, is that a lab test rules out other diseases, which protects patients from receiving inappropriate or potentially harmful treatments.
In addition, Glaser said, a positive diagnosis allows patients to participate in clinical trials of investigational drugs used against the worst consequences of the disease. One drug, an antibody known as Omr-IgG-am, will be tested at UC Davis Medical Center.
With West Nile virus cases expected to peak in California this year, Glaser said it's more important that West Nile patients enroll in the trials.
"I have pleaded with infectious-disease doctors," she said. "This is going to be our big year, and we may not have another one. As this disease becomes more sporadic, we will never be able to get those trials done."
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