West Nile Cases Continue to Spring Up, Despite Mosquito Season Drawing to a Close

The Centers for Disease Control and Prevention (CDC) has reported that 47 states and the District of Columbia have seen West Nile virus activity in either people, birds or mosquitoes, as well as 875 human cases of West Nile virus this season, as of September 19, 2017. Of these cases, 338 were non-neuroinvasive infections and 537 were neuroinvasive infections, such as meningitis or encephalitis. In 2016, the United States saw 2,038 human cases of West Nile virus, compared with 2015, when the US saw 2,175 cases. It will be months until the CDC has preliminary totals for 2017, as new infections can continue to occur through the fall months.

On September 19, the Illinois Department of Public Health (IDPH) reported the state’s first West Nile death of the season. The case involved a resident of Kankakee County who died after testing positive for the virus earlier in the month. So far, the CDC has reported 26 human cases of West Nile in Illinois this season, whereas last year, the IDPH says they saw a total of 155 human cases of West Nile, resulting in 6 deaths. The Aedes and Culex mosquito species that primarily transmit the virus will remain active as the weather stays warm, and can cause new infections well into autumn.

“Although we will soon start seeing cooler weather, West Nile virus is still a concern,” said IDPH director Nirav D. Shah, MD, JD, in a recent statement. “It’s important for everyone to continue taking precautions like using insect repellent, wearing long sleeve shirts and pants, and staying indoors between dusk and dawn.”

In California, the County of Los Angeles Department of Public Health recently announced in a report that in the week ending on September 15, there were 16 new human cases of West Nile documented in the county, while a case reported in the previous week resulted in death. That case involved an area resident with an underlying health condition, who developed a neuroinvasive form of West Nile virus following infection. Los Angeles County has seen an increase in the number of cases resulting in illness compared with the previous 5 years, notes the report. In the area of Los Feliz and Glendale, which has reported 12 cases of West Nile, officials from the Greater Los Angeles County Vector Control District (GLACVCD) announced that they will be going door-to-door on September 20th to warn area residents about the dangers of the virus and educate them on how to prevent infection. “It may seem silly to some people to worry about mosquito bites,” said the GLACVCD’s Levy Sun, in a recent press release. “But no one forgets when they or a family member becomes sick with West Nile virus.”

Elsewhere in the country, the South Carolina Department of Health and Environmental Control confirmed that the state has seen 19 human cases of West Nile virus this season, including the first case this year in the city of Myrtle Beach, which was reported on September 15th. In Texas, where the Houston area is still recovering from Hurricane Harvey, the Department of State Health Services reported on September 19th that they are conducting aerial spraying in an effort to control the mosquitoes carrying viruses such as West Nile and Zika following record-breaking flooding.