Editor’s note: Included in this month’s issue is coverage of the West Nile Virus outbreak. PCT’s coverage includes the latest data from the Centers for Disease Control, and interviews with PCOs and Dr. Jerome Goddard, entomologist, Mississippi State University. PCT also checked in with Dr. Jorge Parada, medical spokesperson for the National Pest Management Association. Below is a Q&A article with Parada, in which he discusses WNV symptoms; how WNV differs from other mosquito-borne diseases; and common misperceptions.
What are West Nile virus symptoms?
I think they key thing to know is that the vast majority of people have virtually no symptoms at all. Virtually 80 percent have no idea they’re infected, don’t seek medical care. We only know if we start doing blood tests for epidemiological purposes.
Four out of five (cases) go unnoticed, and it’s only 20 percent of people who develop symptoms, and most tend to have a mild (case of the) disease with some combination of fever, headache, body aches, gastrointestinal symptoms, nausea, vomiting. Some people will have a slight rash, typically more on the chest, stomach, back, central sort of rash, not so much on the arms. The intensity of this will be very little, to feeling like they have the flu. Those people other than with some headache and disorientation don’t have a lot of the neurological symptoms.
Less than one percent develop the serious symptoms that we associate with WNV: high fevers, more acute headache, and additional neurological symptoms – neck stiffness, confusion, disorientation, coma, convulsions. Very typical muscle weakness with numbness and paralysis that tends to be ascending paralysis, meaning it starts at the feet and works its way up (the body). These are the patients that are hospitalized, and unfortunately, this is the group where we see the deaths.
How does WNV differ from other mosquito-borne illnesses?
It can sometimes be difficult, in that there are other encephalitides, infections that can give you inflammation of the brain, transmitted by mosquitos. St. Louis Encephalitis, eastern equine encephalitis, etc.
There’s a series of them that have existed and have been recognized in the United States for some time. They do tend to have a little bit more localized geographic distribution. West Nile is different in that it is far more common than any of these others. It can be caught all over the continental United States. It’s far more common and has far greater distribution. The other thing about West Nile is, it didn’t used to exist in the U.S. This is an infection that was found in Africa and the Middle East, and was nearly certainly imported from the Middle East, either by an infected mosquito who hopped on board a plane or a person who had the virus in their bloodstream and when they arrived in New York, local mosquitos started spreading it around.
It’s quite clear that it started in the New York area, it just spread across the states.
What are some common misperceptions about WNV?
I want to make a point, people need to understand that West Nile virus is only an incidental human infection. It’s an infection that’s really spread among birds. Mosquitoes to birds, birds to mosquitoes, mosquitos to birds. Typically crows and jays. When West Nile first swept across the country, there was some degree of die off of jays and crows.
Understanding what happens with West Nile, not just humans catching the disease, one has to take into account what’s happening to mosquito populations and what’s happening to bird populations. It is not a person-to-person spread infection, unless you’re donating blood or your organs, you can’t be giving it to someone else. So if a friend or loved one has it, no one should have any fear in going to visit them, caring for them, hugging them. That is not a means of transmitting.
Take precautions, everybody knows to avoid mosquito bites. Wear long sleeves, fix your screens, wear some Deet.
How much water is needed for mosquitoes to multiply?
That's another thing people underestimate. They can multiply quickly, and in less than an inch of water. So if there are some pots out in the yard, potting plants that have sitting water in them, old tires in the corner, mosquitoes will breed. It’s enough that there are infected mosquitoes, we don’t need a mosquito-making machine in our backyard.
Also gutters, even if they’re not completely blocked, enough so that a pool of water will be sitting up in the gutter. Gutters serve as breeding spots for mosquitoes.
The elderly, weakened, immune-compromised people, they should take extra precautions. The risk is much greater if you’re older for getting the BAD case of West Nile.