West Nile Virus in 2012: A Year to Remember

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Posted on November 12th, 2012 by Sharon Gripp in General

It is November and we can finally say good-bye to Pennsylvania’s West Nile Virus season. 2012 will be remembered for the early horse detection in March and the record number of positive detections since surveillance started in 2000.Unfortunately for the human victims of West Nile Virus, some may be living with the serious effects of encephalitis for many years.

Final 2012 Surveillance Numbers for Pennsylvania

West Nile Virus was first found in the United States in 1999 in New York City. Surveillance was then started in Pennsylvania for the 2000 season. After a high detection rate in 2003, West Nile virus seemed to simmer down. In 2010 positive detections in mosquito samples exceeded 1,000; however, the other detections in humans, birds, and veterinary seemed to remain stable. All that  changed in 2012, when positive mosquito detections exceeded 3,400! Human and veterinary detections were the 3rd highest and bird detections was 4th highest since 2000. The data in the table below came from the surveillance reports on Pennsylvania’s West Nile Virus Control Program website.4

Year Positive Counties Humans Birds Mosquito Samples Veterinary
1999 WNV is found for the first time in the USA in New York.
2000 19 0 37 (46 Pools) 1
2001 17 3 361 43 7
2002 63 62 1,437 674 97
2003 67 237 546 954 546
2004 46 15 46 163 9
2005 33 25 23 276 0
2006 48 9 55 234 2
2007 25 9 10 223 1
2008 37 14 14 518 2
2009 33 0 10 279 2
2010 37 28 20 1,057 7
2011 59 6 49 1,262 12
2012 52 48 135 3,410 51

What Happens If I Get Bitten by an Infected Mosquito?

First, the good news. Most people (80%) who do get infected with West Nile Virus will NOT develop any kind of illness. The vast majority of the those that do develop an illness get West Nile Fever. Symptoms include fever, headache, tiredness, and body aches, occasionally a skin rash, and swollen lymph glands. West Nile Fever symptoms generally only last a few days but can linger on for several weeks.2

Less than 1% of the people infected with the West Nile Virus will develop the severe disease called West Nile encephalitis or meningitis, or West Nile poliomyelitis. These symptoms include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. People over the age of 50 and some immunocompromised persons are at the highest risk for getting severely ill if infected with West Nile Virus. The symptoms of encephalitis or meningitis may last several weeks, and neurological effects may be permanent.1, 2

This year, Pennsylvania had 48 human cases. Twenty-two cases were classified as West Nile Fever and twenty-six cases were encephalitis/meningitis. Unfortunately, 4 people died from the disease. Across the country,  5,054 people were infected with West Nile Virus; Texas was hit the worse with almost 1,700 cases.3, 6

Pennsylvania Activities and National Standing

The Pennsylvania West Nile Virus Control Program completed 75,183 mosquito control events and took 28,621 samples. This was certainly a busy year! The Program also received 2,056 complaints and provided over 156 educational events. The public also reported 697 dead birds.5

Nationally, Pennsylvania was in the top 3 in number of positive detections for mosquito, veterinary, and bird samples. However, the effort of all the West Nile Virus partners throughout the state and the broad public participation kept the human case count at 18th and not in the top 2 or 3. 5, 6

We all hope 2012 was an unusual year and not the norm for future years. For right now, it is good to see winter coming so we can finally say good-bye to all those mosquitoes!

Until next time,
Be Safe!

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References:

1 Centers for Disease Control and Prevention. Cases of West Nile Human Disease.

2 Centers for Disease Control and Prevention. Symptoms of West Nile Virus.

3 Pennsylvania West Nile Virus Control Program. 2012 West Nile Human Summary Data.

4 Pennsylvania West Nile Virus Control Program. Surveillance Data and Maps.

5 Pennsylvania West Nile Virus Control Program. “West Nile Virus 2012 Summary.” News Release. October, 11, 2012.

6 U.S.Geological Society. West Nile Virus Disease Maps.