Advancing Virus: West Nile Virus
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RAY SUAREZ: The nation’s largest outbreak of the mosquito-borne West Nile virus continues to spread. Yesterday, Arkansas became the latest state to report a likely case of human illness due to the virus. This summer, the virus has been detected in 34 states and the District of Columbia.
Worst hit is Louisiana, where five people have died, the most recent death reported earlier today. Over the weekend, Governor Mike Foster declared a state of emergency. In Louisiana and three other states– Arkansas, Mississippi, and Texas– more than 100 people are reportedly ill from the virus.
West Nile typically infects birds, but it is spread by mosquitoes, and can be passed along to people. The elderly and people with weakened immune systems are most susceptible to serious illness and death.
For the latest about the West Nile virus, I’m joined by Dr. Julie Gerberding, Director of the Centers for Disease Control; and David hood, Secretary of the Louisiana Department of Health and Hospitals.
Secretary Hood, we’ve gotten word of the latest death in your state. Are more people also turning up sick?
DAVID HOOD: Well, the total number of confirmed cases right now stands at 71. That’s up from 58. So we’re seeing a rather rapid increase in the number of cases.
RAY SUAREZ: Do you suspect that the real number is actually higher but because of symptoms people may think they have other illnesses?
DAVID HOOD: That’s entirely possible. In every case where West Nile virus is impacting a locality, you’re going to see more people who actually have been infected by the virus but may not have symptoms.
RAY SUAREZ: This is a disease spread by mosquitoes. Has this been a particularly heavy mosquito year, Louisiana?
DAVID HOOD: Well, it’s probably no worse than any other year in terms of the total number of mosquitoes. It’s the fact that some of them are infected with West Nile.
RAY SUAREZ: So how is the state responding?
DAVID HOOD: Well, we started our response actually very early on. We found evidence of West Nile last year and had a human case near New Orleans. So we knew it was coming and we expected it in 2002. Last spring we stepped up our surveillance activities, monitoring birds and also mosquito pools. We’ve also been doing very extensive spraying in local areas.
RAY SUAREZ: I saw the spraying trucks moving around the state, but two adjectives that I think pretty fairly describe Louisiana is warm and wet, which is mosquito friendly. Can you really kill enough of them to turn back the threat of the disease?
DAVID HOOD: You can’t totally eradicate it. We can mitigate it. We can try to minimize it, and we’re doing everything we can to do that, but the CDC scientists tell us that there’s no way that we could ever eradicate it totally. This is a permanent condition in Louisiana and probably in the United States as well.
RAY SUAREZ: So what are you telling the people of Louisiana to do? Should they follow new habits, new ways of life?
DAVID HOOD: Well, I think it’s something that they’re going to adapt to because this is sort of going to be with us from time to time from now on. And it’s similar to wearing seat belts when you’re in a car. People need to take personal responsibility and take precautions, and that involves wearing an insect repellent with the ingredient Deet in it and also making sure they don’t have any standing water in their yard and neighborhood.
RAY SUAREZ: Are there people who are also panicking, staying at home when they might otherwise go out, keeping other family members at home? How do you strike a balance if you live in a place where mosquitoes are prevalent between your real risk and self-protection?
DAVID HOOD: Well, it does. The reaction so far runs the gamut between people who are afraid to leave their house and people who are totally unconcerned. What we want is people to be concerned and to follow the message that we put out about personal responsibility. If they do that, they can right on with their normal life.
RAY SUAREZ: Dr. Gerberding do we know how the West Nile virus came to the United States and where it came from?
DR. JULIE GERBERDING: No. We can only speculate on how it got here. We know this is an infection problem in other parts of the world. It’s carried in birds. It’s carried in mosquitoes and so there are a lot of possibilities about how it first arrived in 1999, but we really don’t know.
RAY SUAREZ: From 1999 and a fairly contained outbreak in New York, it’s now moved on to a big chunk of the country. How does it do that?
DR. JULIE GERBERDING: Well, it is very effectively transmitted from one bird to another by mosquitoes. You know, birds migrate and so as the birds move from one location to another so does the virus.
As it’s moved both South and West, it’s been established in parts of the country that have much milder winters and in locations where mosquitoes can remain active for much longer periods of time. So that kind of sets the stage for the transition that we’re seeing: Moving South, moving West and then entering a new population as it progresses.
RAY SUAREZ: It’s really the mosquito that’s doing all the work spreading this thing around. Birds don’t give it to other birds. Animals don’t give it to other animals?
DR. JULIE GERBERDING: The most important component of spread really is that mosquito bite.
RAY SUAREZ: So when we talk about this disease being here in the United States, do you mean here to stay?
DR. JULIE GERBERDING: I think it’s very hard to imagine how we would eradicate this altogether. Mosquitoes are ubiquitous. Birds are everywhere. And it probably is going to be one of those illnesses that we have to learn to live with and that will be a problem at least from time to time.
But we certainly can do a lot to try to minimize its impact on humans and many of those measures are already successfully underway in the states that are affected this year.
RAY SUAREZ: Do we know why some people get very mild symptoms from contracting this virus while other people develop encephalitis and a smaller number still die?
DR. JULIE GERBERDING: We don’t know. Fortunately most people who are infected are completely asymptomatic. They have absolutely no sign of the illness. About one in 150 infected people do develop the more severe illness with the meningitis or encephalitis. Those tend to be older people or people with compromised immune systems. But what makes a difference is just not known at this time.
RAY SUAREZ: Are we learning things though? I mean, I remember when this first started to be reported about, the idea was given out that really the elderly and the very young had a lot to worry about but other people didn’t. Now that more people are getting this disease is the profile broadening a little bit?
DR. JULIE GERBERDING: Well, we are concerned this year that it does seem to be affecting younger people than it has in the past years. So we’re keeping a very close eye on that. But I think it’s also true that as illnesses spread from one geography to another, their pattern sometimes does change.
One of the things CDC is doing is supporting some of the activities in the states, in particularly Louisiana we’re doing some work to try to understand better what are the risk factors, why do certain people get it and certain other people don’t. So we will hope to learn as we go with this.
RAY SUAREZ: Well, if tomorrow morning somebody who is watching this program wakes up with a fever or swollen glands, some of the other symptoms mentioned and they live in one of those 34 states, should they get a blood test?
DR. JULIE GERBERDING: I think if someone wakes up with a fever, particularly a high fever and a severe headache, that’s an indication to go to the emergency room and see a clinician. It may not be West Nile but it’s a kind of symptom complex that warrants medical attention regardless of what’s causing it so the real characteristics of the severe illness are that worst headache you’ve ever had in your life accompanied by a high fever.
RAY SUAREZ: And do we know… can we track accurately when a disease mimics the symptoms of so many other human illnesses just how many people are getting this?
DR. JULIE GERBERDING: Well, we do have methods for diagnosis. The laboratory test methods are proving to be very reliable but one of the most important things about this particular infectious disease is that we can predict where it’s going to go because we can find it in the mosquitoes and in the dead birds first.
That’s how we know it’s already in 34 states. So those are the states that are gearing up their mosquito control programs in anticipation of increased virus activity, and that alone is a big step toward reducing the number of infected people.
RAY SUAREZ: Is there a vaccine or a medicine to treat it once it’s been contracted?
DR. JULIE GERBERDING: Right now there is no vaccine and we really don’t have specific therapy to treat the infection. The treatment is primarily hospitalization, hydration and the usual kind of supportive care that we can give to people with severe illnesses.
RAY SUAREZ: Should we also be worried about animals? I mean, horses get this disease. Do other livestock get it? Could this be an economic threat as much as something that also threatens human health?
DR. JULIE GERBERDING: Well again the mosquito abatement programs will help a lot to protect both people and livestock. But it certainly can infect animals. Horses are the population that’s been most affected, but the virus has been found in a wide variety of other animals and many, many, many birds. We have to continue to ask the question, where is it now? And part of that involves checking ill animals and also checking dead birds to see if they might be carrying it.
RAY SUAREZ: And what kind of weather pattern, Secretary Hood, for the rest of the year would help you out in Louisiana, help you ride this thing out?
DAVID HOOD: Well, certainly the weather we’ve had for the past few days has not been helpful at all: Torrential rains basically, and that’s going to complicate the standing water problem. So it just means that people have to be more vigilant about clearing the standing water out of their neighborhoods, and of course they have to continue to wear insect repellent. Those are the things that are going to make a difference.
RAY SUAREZ: Secretary Hood, Dr. Gerberding, thank you both.
DAVID HOOD: Thank you.
DR. JULIE GERBERDING: Thank you.