West Nile virus cases start earlier, are more severe this year

West Nile virus was first identified in the United States in 1999 in New York. Since then, it has spread throughout the country, peaking with almost 10,000 cases in 2003. The virus is the leading cause of mosquito-borne disease in the contiguous United States. Each year, there are several thousand cases of West Nile virus and around 100 deaths on average.

Although most people infected with West Nile virus do not experience any symptoms, around 20% will experience a fever, headache, body aches, joint pain, vomiting, and diarrhea. A small portion of people infected with the virus (less than 1%) will develop severe symptoms that affect their nervous system, such as encephalitis or meningitis. Adults ages 60 and older and those with underlying medical conditions have an increased risk of severe illness.

As of June 30, CDC reported at least 48 cases of West Nile virus, of which 38 cases were severe. This is the highest number of cases for this time of year since 2004. Usually, an average of 10 cases of West Nile virus are reported by the end of June. 

How to stay safe from West Nile virus this summer

Currently, there are no vaccines or disease-specific treatments for West Nile virus. Instead, CDC recommends patients treat the infection by resting, drinking plenty of fluids, and taking over-the-counter medications. Those with more severe symptoms may need to be hospitalized.

According to Daniel Pastula, chief of neuro-infectious diseases and global neurology at the University of Colorado-Anschutz and the Colorado School of Public Health, the best protection against West Nile virus is vigilant prevention.

Some tips to reduce the risk of mosquito bites include:

• Eliminating sources of standing water around your home and yard, since they can be breeding grounds for mosquitoes
• Treating water that can't be dumped, like ponds and storm drains, with larvicides called mosquito dunks
• Using traps to capture adult mosquitoes
• Cooling your home with air conditioning instead of opening windows, if possible
• Repairing any damaged window screens
• Wearing insect repellent registered with the Environmental Protection Agency when outside, particularly around sunrise and sunset when mosquitoes are most active
• Wearing long pants and long sleeves when outside

Pastula also called for the federal government to provide more financial support for local mosquito control programs, as well as fund development for a West Nile virus vaccine. So far, the only West Nile virus vaccines are for horses. Although some vaccines for humans have had promising results in early-stage clinical trials, none of them have been tested in late-stage human trials.

"Improving support and funding for vaccine development, particularly West Nile virus, is incredibly important to help reduce the burden of disease," Pastula said.