Arbovirus infection targets children

If you think that West Nile virus (WNV) is the most common cause of neuroinvasive arboviral disease in juveniles, think again.

Even though WNV is the most common cause of neuroinvasive arboviral disease in the United States, La Crosse virus (LACV), named for the town in Wisconsin in which it was first identified, is the virus most responsible for arboviral disease among children, according to a report from the Centers for Disease Control and Prevention (CDC).

With WNV, the highest incidence of neuroinvasive disease occurs among seniors aged 70 years or older and then among adults in general, but neuroinvasive disease caused by LACV overwhelmingly occurs in children aged younger than 16 years.

In fact, of the 130 LACV cases reported by the CDC from 81 counties in 14 states in 2011, 95% occurred in children aged younger than 18 years (median age, 8 years).

To make matters worse, 89% of the cases were considered neuroinvasive (up 73% from 2010), 91% required hospitalization, and 1 was fatal. The highest incidences of neuroinvasive disease occurred in West Virginia, Ohio, and North Carolina. Those 3 states combined reported 78% of the cases.

Both WNV and LACV are among a family of arthropod-borne viruses transmitted to humans primarily through the bites of infected mosquitoes and ticks. Other viruses in the group include Powassan virus, which is transmitted by ticks, and St. Louis encephalitis virus, Eastern equine encephalitis virus, Jamestown Canyon virus, and Western equine virus, all of which are transmitted by mosquitoes.

Because no specific treatment exists, experts say that physicians often do not order the tests required to identify LACV; the diagnosis is listed as aseptic meningitis or viral encephalitis of unknown etiology, leading to underreporting.

There is no vaccine for LACV, so to avoid infection, children should be counseled to reduce playing outdoors, particularly in early evening hours, to wear long shirts and pants while outside, and to apply mosquito repellent to exposed skin.

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