US Outbreak Of West Nile Virus Largest Ever
August 23, 2012

US Outbreak Of West Nile Virus Largest Ever

Lawrence LeBlond for - Your Universe Online

A deadly outbreak of West Nile in the United States is the largest ever recorded, with 47 deaths and thousands people infected in at least 38 states, according to estimates from the US Centers for Disease Control and Prevention (CDC).

West Nile usually peaks in mid-August, and any new infections usually take a few weeks to show up in estimates, yet the CDC is expecting cases to rise dramatically, in what is being hailed as the worst outbreak since the disease was first reported in the US in 1999.

Dr. Lyle R. Petersen, director of the Division of Vector-Borne Infectious Diseases at the CDC, said many more cases will likely occur, as the numbers of infected people have already risen substantially in the last few weeks. Just one month ago, he noted, a mere 29 cases of West Nile had been detected. As of Tuesday, 47 of the 50 states had reported indications of the virus in humans or animals. Only Alaska, Hawaii, and Vermont have yet to report any indications of the virus.

Prior to this year, the worst year for West Nile occurred in 2003 with 9,862 cases reported and 264 deaths. While the death toll this year has yet to breach 100, the high number of possible infections could likely prompt death tolls to rise dramatically over the next several weeks.

The problem is far from over. August is the prime time for mosquitoes -- and nearly all West Nile virus infections come from mosquito bites. The counts usually rise through September.

Petersen said the reason for the high number of cases this year remains unclear, but the unusually warm weather could have offered favorable conditions for the disease to transfer to humans.

Petersen said the bulk of the cases, nearly 75 percent, are in Texas, Mississippi, Louisiana, South Dakota and Oklahoma. Texas has remained the epicenter of the outbreak, with 21 of the 47 reported deaths occurring there, according to the Texas Dept. of State Health Services.

David L. Lakey, MD, Texas state health commissioner, characterized the situation as a "disaster."

“It is not just about the numbers. This disease impacts the lives of hundreds if not thousands of people, and their lives will be changed by this outbreak. Our hearts go out to them,” Lakey told WebMD´s Daniel J DeNoon.

While it remains unclear why so many people have become infected this year, the CDC is investigating one possible reason: the virus may have mutated into a more dangerous form.

Petersen said that more than half of the cases this year have become neuroinvasive, meaning the infection has spread to the brain in these patients.

Health departments are on high alert and are taking necessary steps to protect blood supply. To date, the virus has been detected in the blood of 242 donors -- donated blood is routinely screened for West Nile virus.

There is good news, however.

According to the CDC, only one in five people infected with West Nile virus gets West Nile fever. Symptoms of West Nile fever appear within two weeks after the bite of an infected mosquito. While West Nile virus has infected numerous thousands of people, only 489 cases of the fever have shown up. Yet, many cases go unreported, meaning those estimates could be low.

Illness appears suddenly, said Petersen, who was infected in 2003.

“I was out for a jog, and in one mile I went from perfectly normal to the point where I could barely walk,” he reported, adding that that is probably the norm for most people.

And the illness is generally not mild or brief. “Those who get more ill with West Nile fever will be laid up in bed for days or a week, followed by a period of just feeling awful. And there can be a fatigue syndrome where people remain fatigued for weeks or months. It lasts longer than we used to think,” Petersen said.

He noted that these people are the lucky ones compared to those who get the “neuroinvasive disease.” Those with neuroinvasive West Nile can wind up with encephalitis or meningitis and can become paralyzed. So far this year, 629 cases have been reported with 58 reported cases of paralysis.

“The meningitis or encephalitis can cause paralysis that affects one or more limbs. It can also affect breathing. It is one of the more severe and dreaded complications,” Petersen said. “With meningitis, symptoms include headache, stiff neck, eye pain, and fever. Encephalitis, infection of the brain itself, causes cognitive problems, where people can't think properly. It can also cause coma, along with all the symptoms of meningitis as well.”

And in some people, West Nile virus doesn´t go away, according to a report last month from researchers at Baylor University. It can hide away in the kidneys and over the course of years, it can lead to kidney disease that worsens over time.

People with neuroinvasive West Nile were most likely to have long-lasting infection and kidney damage. But this also happened to about 9 percent of those with mild or no symptoms as well. Petersen noted that these findings have yet to be confirmed in other lab settings.

It is important to know some basic facts about West Nile and who is most at risk.

In areas where mosquitoes carry the virus, only about one in 500 mosquitoes is infected, according to the Connecticut Mosquito Management Program.

Of those who do get bit by an infected mosquito, about 80 percent do not get sick, according to the CDC. About 20 percent will have mild symptoms. Severe illness occurs in less than 1 percent of those who are bitten. Severe illness leads to coma, paralysis and death.

You can protect yourself from mosquitoes by using a repellent with DEET. Also, dress in long pants and long sleeves for added protection. Mosquitoes are most active at dusk and dawn so taking extra precautions during these times is key to avoiding an infectious bite. Standing water is a breeding ground for mosquitoes and should be avoided. Drain kids´ pools and birdbaths to further protect yourself.

People most at risk for West Nile infection are those 50 and older; this group of people are also at risk for developing the most severe illnesses and should take extra care in avoiding mosquitoes, according to the CDC.

The most important thing is to seek medical attention if you have severe headaches or confusion, which could be a sign of an infection. Severe illness usually requires hospitalization. Milder cases improve on their own and do not necessarily require medical attention.