West Nile Affecting Many US States

West Nile virus infections reported this summer causing neuroinvasive disease in some cases

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Preventing a mosquito's bite can sometimes mean more than preventing an annoying itch. A new official update provided insight into this summer's cases of one mosquito-borne illness.

West Nile virus, which is spread by infected mosquitos, often causes no symptoms, but it can be deadly for some patients.

The Centers for Disease Control and Prevention (CDC) reported that 82 West Nile infections have been discovered in people across the US so far this year.

"Wear long clothing to help protect your skin from mosquitos."

According to the latest update from the CDC, 37 states and the District of Columbia have reported cases of West Nile virus so far this year in either humans, birds or mosquitoes.

Eighty-two human cases of the illness have been reported in 18 states. California has reported the most cases (19), followed by Arizona (13), South Dakota (12) and Louisiana (11).

According to the CDC, between 70 and 80 percent of people who are infected with West Nile do not experience any symptoms. Many of these patients likely do not realize they are ill.

In about 1 out of 5 West Nile patients, symptoms like fever, aches, vomiting, diarrhea, joint pain, and weakness develop and may linger for weeks to months.

In less than 1 percent of West Nile virus cases, neuroinvasive disease develops. This can include conditions like encephalitis (swelling of the brain) or meningitis (swelling of the membranes around the brain and spinal cord). The CDC noted that symptoms of neuroinvasive West Nile virus may include a high fever, stiffness in the neck, disorientation, seizures, paralysis or coma. The patient dies in an estimated 10 percent of these cases.

Of the reported cases so far in 2014, 39 (47 percent) were considered neuroinvasive disease. The remaining 43 (53 percent) were considered non-neuroinvasive. Four cases have lead to deaths — two in Arizona and one each in Louisiana and Missouri.

The CDC recommends a number of methods to help prevent mosquito bites and protect against West Nile virus and other illnesses carried by the insects, including wearing long sleeves, pants and socks when possible.

The CDC also suggests using certain insect repellents outdoors.

"Repellents containing DEET, picaridin, IR3535, and some oil of lemon eucalyptus and para-menthane-diol products provide longer-lasting protection," the CDC noted on its website. "To optimize safety and effectiveness, repellents should be used according to the label instructions."

The CDC reported that most people in the US who become ill with West Nile are infected between the months of June and September. In most cases, people become ill between two and six days after being bitten by an infected mosquito — although this "incubation period" can be longer in some cases.

Review Date: 
August 11, 2014
Last Updated:
August 12, 2014