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The West Nile Virus arrived in North America in 1999, likely brought in by a viremic visitor, and over a period of a few short years managed to spread across the entire United States and make inroads into Canada.
From the USGS Factsheet on West Nile Virus
While some years are worse than others, each summer thousands of people are infected via mosquito bites in the United States. Fortunately, about 80% of those infected with WNV experience at worst only mild, or sub-clinical symptoms. Most of the rest may experience a brief febrile illness (West Nile Fever). Both are likely highly underreported.
A very small percentage (perhaps 1%) may develop WNV neuroinvasive disease (WNND), a form of encephalitis that can sometimes prove fatal. Those over the age of 50 appear to be the most vulnerable to the most serious form of the illness, and as most of those are hospitalized, those numbers are more solid.
In 2012 – the worst year for West Nile deaths thus far – the CDC reported:
Final 2012 West Nile virus update:
In 2012, all 48 contiguous states, the District of Columbia, and Puerto Rico reported West Nile virus infections in people, birds, or mosquitoes. A total of 5,674 cases of West Nile virus disease in people, including 286 deaths, were reported to CDC. Of these, 2,873 (51%) were classified as neuroinvasive disease (such as meningitis or encephalitis) and 2,801 (49%) were classified as non-neuroinvasive disease. The numbers of neuroinvasive, non-neuroinvasive, and total West Nile virus disease cases reported in 2012 are the highest since 2003.
Last year, only 85 deaths were reported, and in 2011 just 43. We really won’t have any idea what kind of West Nile season we are going to see yet for a couple of month. But today, Texas has reported their first confirmed neuroinvasive West Nile case of the year.
Texas Reports Year’s First West Nile Case
News Release
May 21, 2015The Texas Department of State Health Services is reporting the state’s first case of West Nile illness this year and reminding people how to protect themselves from the mosquito-borne virus that causes it.
A patient in Harris County has been diagnosed with West Nile neuroinvasive disease, the more serious form of illness. DSHS won’t release additional personal details in order to protect the patient’s identity. To reduce the chances of a mosquito bite that can transmit West Nile virus, people should:
- Use an approved insect repellent every time you go outside and follow the instructions on the label. Among the EPA-approved repellents are those that contain DEET, picaridin, IR3535 and oil of lemon eucalyptus/para-menthane-diol products.
- Regularly drain standing water, including water collecting in empty cans, tires, buckets, clogged rain gutters and saucers under potted plants. Mosquitoes that spread West Nile virus breed in stagnant water.
- Wear long sleeves and pants at dawn and dusk when mosquitoes are most active.
- Use air conditioning or make sure there are screens on all doors and windows to keep mosquitoes from entering the home.
“Up to 80 percent of people who contract the virus don’t get symptoms and won’t even know they have it,” said Dr. Tom Sidwa, state public health veterinarian and manager of DSHS’s zoonosis control branch. “But those who do get sick can experience very serious effects ranging from fever to substantial neurological symptoms and even death.”
Symptoms of the milder form of illness, West Nile fever, can include headache, fever, muscle and joint aches, nausea and fatigue. People with West Nile fever typically recover on their own, although symptoms may last for weeks to months. Symptoms of West Nile neuroinvasive disease can include those of West Nile fever plus neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness and paralysis.
There are no medications to treat or vaccines to prevent West Nile virus infection. People over 50 years old and those with other health issues are at a higher risk of becoming seriously ill or dying when they become infected with the virus. If people have symptoms and suspect West Nile virus infection, they should contact their healthcare provider.
Health officials are also monitoring cases of another mosquito-borne virus, chikungunya. Seven Texas residents have been diagnosed with chikungunya this year. So far, all Texas cases have been acquired by people travelling abroad in areas where the virus is more common, particularly the Caribbean. The same precautions apply, and DSHS encourages travelers to take steps to avoid mosquito bites.
Last year, there were 379 human cases of West Nile illness in Texas, including sixdeaths. DSHS will regularly update case counts at www.dshs.state.tx.us/news/updates.shtm.
As we do every summer, we’ll be following the spread of mosquito-borne pathogens such as Dengue, Chikungunya, Malaria, WNV, SLEV, and EEE along with tickborne diseases like Lyme, SFTS, and the Heartland Virus.
With the Memorial day weekend coming up, and a long summer ahead, it is important to remember the 5 `Ds’ of prevention:
