2012 One Of The Worst Years For West Nile Virus In US History
October 5, 2012

2012 One Of The Worst Years For West Nile Virus In US History

Lawrence LeBlond for redOrbit.com - Your Universe Online

Newly released West Nile virus data suggests 2012 is on par to becoming one of the worst years for the virus in US history. As of October 2, all 48 contiguous US states have reported infections in people, birds or mosquitoes. And of the 3,969 cases of the disease infecting humans, 163 have resulted in death, according to the US Centers for Disease Control and Prevention (CDC).

This year´s outbreak is the largest through the first week of October since 2003. According to CDC figures, there were 9,900 WNV infections and 264 deaths in 2003. For the current year´s outbreak, 51 percent of the cases seen were classified as neuroinvasive disease (leading to meningitis and encephalitis); the remaining 49 percent (1,959 cases) were classified as non-neuroinvasive disease (commonly known as West Nile fever).

A spokesperson for the CDC told CBSNews.com that it is hard to predict how many more cases will be identified throughout the remainder of the year. The disease usually peaks in August and cases generally begin to fall thereafter.

About 80 percent of people who become infected with the virus will go on without any symptoms, but 20 percent may develop a fever, headache, vomiting, rash and other relatively mild symptoms. But about 1 in 150 will go on to develop severe neuroinvasive illness, with high fever, stiffness in the neck, convulsions, vision impairment, coma and even death. People most at risk are those over 50 and those with compromised immunity.

So far this year, 70 percent of the cases have been confined to just eight states--Texas, California, Louisiana, Mississippi, South Dakota, Michigan, Oklahoma and Illinois; a third of all cases have been reported from Texas.

Dr. Lyle Petersen and Dr. Marc Fisher of the CDC noted in this week´s issue of NEJM that it is likely West Nile virus will remain unpredictable for the foreseeable future. While reports this year are about the same as those reported in 2002, the doctors said it is six times the number seen in 2011.

“Until this year´s resurgence, many experts questioned whether West Nile virus would remain a substantial public health concern,” Petersen and Fischer wrote. However, the knowledge the CDC has on viruses similar to WNV suggests it “will cause sporadic cases and unpredictable outbreaks big and small for decades to come,” they added.

“Thus, generating long-range predictions regarding West Nile virus outbreaks will be a formidable, if not impossible, task,” they said.

There are no treatments and no vaccine for West Nile. The sporadic and widespread nature of the disease makes it difficult for researchers to conduct trials that would include enough people to prove a treatment is effective, the duo explained.

Currently the best options for protecting yourself, your family and your pets is to remain indoors during peak hours when mosquitoes are most active, typically at dusk and dawn. If you do go outside, wear long sleeve shirts and also use an insect repellent with DEET.

Mosquitoes breed in standing water and it is a also a good idea to remove any objects from your house that can be potential breeding cesspools for mosquitoes, i.e. old tires, birdbaths, open garbage cans or buckets.