Some experts hold out hope for a vaccine. Monath said Acambis has manufactured its West Nile vaccine by splicing two of the virus’s outside proteins into a modified yellow fever vaccine, a strategy that has worked in a vaccine against dengue. Monath said that tests of the vaccine in monkeys have gone well.
Proving that a vaccine is really effective, however, won’t be easy. As the CDC’s Campbell pointed out, a scientifically valid clinical trial of the vaccine requires a large number of people exposed to the virus. “If we had thousands of cases a year, and we could predict where they were going to be, then yes, a vaccine could be very useful,” said Duane Gubler, director of the CDC’s Division of Vector-Borne Infectious Diseases. (The CDC is independently trying to develop a West Nile virus vaccine.) The problem is, Gubler added, no one can yet predict where West Nile will break out next.
There was an awkward moment when I first met Bennie and Yvonne at ChristMedicalCenter. We were seated around a conference table in Wichter’s office, and I asked Bennie if he felt back to normal after half a year. “Almost,” he said with a shrug, “but still a little foggy.” As he spoke, Yvonne was shaking her head. “His mind is not right, not back to normal,” she said with surprising bluntness, “just in terms of his thought processes and forgetfulness.”
The observation was anecdotal, but it echoed the results of a study by Denis Nash and colleagues at the New York City Department of Health, who found that only 37 percent of the people who developed West Nile meningitis or encephalitis in the original 1999 outbreak had fully recovered after 12 months. The finding raises questions about the longterm effects of West Nile infection, and whether there might be any more surprises in the clinical picture.
McNamara said something that might qualify as yet another whisper from the animal kingdom worth looking into. “We had a rhino that was symptomatic in September of 1999,” McNamara said. It recovered, but after it died some months later of an unrelated physical injury, McNamara’s department did a postmortem and were startled to find that the animal’s brain had remained inflamed, indicating ongoing damage from West Nile infection. Later, she examined two cranes that had previously been infected, but had shown no signs of illness. Their brains, too, bore signs of encephalitis. “So I thought, ‘Whoa, I have symptomatic and nonsymptomatic animals that have evidence of encephalitis,’ ” McNamara told me. “What does that mean for us?”