Mosquitos and Ticks Spread Illness to Thousands Last Year

West Nile virus and other tick and mosquito borne illnesses caused cases of neuroinvasive disease

(RxWiki News) The buzz of a mosquito or the itch of its bite can be annoying, but in some cases, that bite may become a serious matter. A new study examined illnesses caused by infected bugs.

The study looked at instances of arthropod-bone viruses, or arboviruses, which are typically spread through the bites of mosquitos or ticks. One such virus is the West Nile virus.

This study found that West Nile virus caused over 2,000 illnesses in the US last year.

"Empty standing water from around your home to reduce the presence of mosquitos."

This study was led by Nicole P. Lindsey, MS, of the Centers of Disease Control and Prevention's (CDC) National Center for Emerging and Zoonotic Infectious Diseases

According to Lindsey and colleagues, arboviruses can sometimes lead to neuroinvasive disease, or cases in which the illness causes serious complications like meningitis or encephalitis. In these situations, the area around the brain and spinal cord becomes inflamed, sometimes causing death.

To examine rates of arboviruses in the US last year, Lindsey and team analyzed data that was reported to the CDC from health departments across the US during 2013.

Of the 3,141 US counties, 830 (26 percent) in 47 US states and the District of Columbia reported instances of arboviruses.

The researchers found that a total of 2,605 cases of arboviral diseases were reported in the US last year, 1,383 (53 percent) of which were neuroinvasive. Lindsey and and team estimated that there were 0.44 cases of neuroinvasive arbovirus for every 100,000 people in the US last year.

According to these researchers, the vast majority (90 percent) of arbovirus patients became ill during the period of July through September. Of the arbovirus patients, 1,494 (61 percent) had to be hospitalized and 119 (5 percent) died.

West Nile virus was by far the most commonly reported arbovirus, with 2,469 cases reported during 2013. Of these cases, 51 percent were considered neuroinvasive cases. Lindsay and and team estimated that in 2013 there were 0.40 cases of neuroinvasive West Nile for every 100,000 people. The researchers noted that this was a decrease from the rate of 0.92 cases for every 100,000 people seen during 2012, when an outbreak occurred in several states. 

La Crosse virus, also a mosquito-borne illness, was the next most commonly reported arbovirus. This condition was tied to 85 cases in the US last year.

Other reported arboviruses included Jamestown Canyon virus, which is mosquito-borne and caused 22 illnesses; Powassan virus, which is carried by ticks and caused 15 illnesses; and eastern equine encephalitis virus, which is spread by mosquitos and caused eight illnesses.

"[West Nile virus] and other arboviruses continue to cause serious illness in substantial numbers of persons annually," wrote the study authors. "Maintaining surveillance remains important to help direct and promote prevention activities."

CDC recommended steps like the use of insect repellent and protective clothing to prevent mosquito bites.

This study was published June 20 in CDC's Morbidity and Mortality and Weekly Report. No conflicts of interest were reported.

Review Date: 
June 20, 2014