This article discusses common questions and answers on West Nile Virus due to the rise in cases recently. This is important due to the neurological complications in serious cases of West Nile Virus.
But for all the fear and concerns in some parts of the country, health officials say the reality is that most people who become infected will not have any symptoms, and of those who do, only a fraction will develop severe illness. To find out more about the disease and the factors fueling the current outbreak, we spoke with Dr. Erin Staples, a medical epidemiologist at the Centers for Disease Control and Prevention.
Is it true that many of the symptoms of West Nile are easily overlooked? How many people probably have it and don’t know it?
From studies we know that only about one in every five people who get infected with West Nile will actually develop symptoms. The most common ones are fever, headaches, body ache, joint pain, vomiting, diarrhea and rash. A lot of people who develop symptoms usually just wait it out at home. Or they’ll go to a medical doctor and end up recovering from their illness and feeling much better within several weeks. Sometimes, people will complain of fatigue or report feeling not quite themselves for several months.
How does a person know if he or she has a more serious form of the illness? What symptoms should prompt you to see a doctor?
Symptoms of severe neurological disease due to West Nile virus infection can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.
Less than 1 percent of people who are infected will develop such symptoms of more serious neurological illness, like encephalitis or meningitis, which is inflammation of the brain or surrounding tissue.
But people with the serious neurological symptoms are more likely to seek treatment and find out that they have it. With the serious neurological symptoms, about 10 percent of people will die as a result.
How do you find out if you have West Nile? Is there a test?
People who have symptoms that concern them should see a health care provider. If they think they have West Nile, they can have their blood tested for the presence of antibodies or, in more severe cases that affect the central nervous system, a doctor can take samples of the cerebrospinal fluid that surrounds the brain and spinal cord.
Usually people are hospitalized if they have more serious symptoms.
Are certain groups at higher risk?
Anyone who is outdoors during times when mosquitoes are active is at a higher risk — so that means people who go outside at dusk and dawn who haven’t done anything to prevent getting bitten, like using repellents or wearing pants and long sleeves.
We do know that there are certain groups that are also at risk of having more severe disease. The groups we’ve identified include people over the age of 50, and people who have medical conditions like cancer, diabetes, hypertension, kidney disease and organ transplants.
We know this from data we’ve collected from state health departments. For a lot of these high-risk groups, it probably deals with their ability to fight infection. You may have people with cancer, for example, who are receiving drugs that inhibit their immune cells. Someone with diabetes may not be able to fight the infection as well as an otherwise healthy person.
With people over the age of 50, it’s most likely that as you age your immune cells are not as robust. We do have a larger proportion of people with encephalitis in the older age group. But anybody who’s out there and not using measures to prevent mosquito bites could be at risk for getting West Nile.
How widespread is the outbreak, and how are you keeping track of it?
The C.D.C. reports numbers once a week. We take a snapshot, and the states know to report to us by Tuesday morning at 3 a.m.So as of Tuesday we knew that there were 1,118 cases of West Nile being reported from throughout the United States, and that included 41 deaths.
Right now, we have received reports of West Nile virus infections or activity in people, birds or mosquitoes in 47 states. It’s pretty much widespread in the continental United States. The states that have not reported any are Hawaii and Alaska, which have never reported any West Nile activity, and then Vermont. Vermont has previously reported cases, just none so far this year.
What is the regional breakdown of cases? Are most in Texas?
Almost half of our cases have been reported in Texas, so that is the most affected region at this point. But about 75 percent of our cases have been reported from five states. The first is Texas, the next is Mississippi, Louisiana, then South Dakota and Oklahoma. The central region of the United States is the main area reporting the most cases, but most states are being affected, just to varying degrees.
How does this compare with other West Nile outbreaks?
We definitely have received reports from state health departments of earlier and greater West Nile activity, particularly in the central states. It’s more than we’ve seen in recent years, and we’re not quite sure why. Essentially there are several factors that play a role, including the weather, the number and types of mosquitoes that spread the virus, birds that also spread the virus, what people are doing to prevent it, and whether there’s community-based spraying. All of those things may determine the size and location of an outbreak. So it makes it very difficult to predict from year to year where we may see West Nile virus outbreaks, because these things change.
Why is this outbreak so severe? Is it the biggest?
There is some thought that the unusual mild winter we had, the early spring and the hot summer, may have fostered some conditions that are favorable to breeding mosquitoes that spread West Nile virus.
What we can say right now is this is the biggest outbreak. If we look at the number of cases reported to the C.D.C. over the last 10 years, through the third week of August, we’ve had an average of 390 West Nile cases reported each year, and that ranged from a low last year of 77 cases to a high in 2004 of 832 cases.
So now, having more than 1,000 cases reported to us this year through the third week of August, we’re up from what we’ve traditionally seen in the past. However, we don’t know how this is going to translate in the end of the year, for instance, if there’s going to be significant changes. Let’s say New York goes into an early frost this year. That could truncate transmissions.
What steps can people take to protect themselves?
Use insect repellents when you go outdoors. Wear long sleeves and pants to prevent mosquito bites at dusk and dawn. Install or repair screens or windows to prevent mosquitoes from getting inside your home. Empty any containers of standing water around your home — things like flower pots, kiddie pools, buckets and sometimes even gutters, which can have standing water in them.
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