ATLANTA (GA) – Although West Nile Virus warnings typically being sounding in early spring with the arrival of the season’s first mosquitoes, health officials say most human infections actually occur in late summer and early fall. Data from the Georgia Department of Human Resources, Division of Public Health, show that over 90% of insect-borne human infections – such as West Nile Virus (WNV) – in Georgia occur in the months of August, September, and October.
"Of course, it’s important to remember that there is potential for West Nile Virus any time mosquitoes are present," said Dr. Stuart Brown, Director of the Division of Public Health. "But late summer and early fall seem to be the times that people are most at risk of becoming infected."
Still, health officials say, predicting where and when West Nile Virus might show up is difficult. Active mosquito surveillance in the five metro Atlanta counties – Fulton, DeKalb, Gwinnett, Clayton, and Cobb – have found larger mosquito pools than usual for this time of year. However, while infected mosquitoes have been found in metro counties as early as May in previous years, this year the first WNV-infected mosquitoes were found in metro Atlanta only last week, when WNV-infected mosquitoes were detected in three Fulton County sites. The WNV team at the Fulton County Department of Health and Wellness has responded by treating problem areas with larvicide and providing source reduction information to people living in affected areas. There has been only one human case of WNV reported in Georgia this year, in Paulding County.
"Because of the human case, we knew there were infected mosquitoes in the state, we knew West Nile Virus was here," said Dr. Rosmarie Kelly, Medical Entomologist with the Division of Public Health. "Even though it has been slower to show up in mosquitoes closer to Atlanta this year, the increased numbers of mosquitoes we’re seeing should be a signal to people to protect themselves. This is the time of year we typically begin to see an increase in human cases of West Nile Virus."
West Nile Virus is spread to humans by the bite of an infected mosquito. In Georgia, Culex quinquefasciatus, the southern house mosquito, is associated with most WNV infection, however many species of mosquito have been known to carry and transmit the virus to humans – including the Asian Tiger mosquito, other Culex species, and some of the floodwater species that can appear after heavy rains.
According to the US Centers for Disease Control and Prevention (CDC), up to 80% of people infected with WNV will have no symptoms, while 20% may suffer from flu-like illness characterized by fever, headache, muscle aches, and vomiting. Approximately one in 150 human infections will result in severe illness such as encephalitis (swelling of the brain), and can include high fever, stiff neck, disorientation, paralysis, and in rare cases, death. While deaths from WNV are rare (since 2001 there have been only 13 deaths in Georgia from WNV), paralysis and other neurological impairments resulting from severe WNV infection can be long lasting or permanent.
Health officials emphasize it is important for people to understand all the risks of West Nile Virus in order to make informed decisions about protecting themselves and their families.
"The risk of any one individual becoming infected and suffering severe illness continues to be very low," said Brown. "But if you don’t protect yourself, if you don’t take steps to reduce your exposure to mosquitoes, you are putting yourself at risk for any range of symptoms associated with West Nile Virus – because it is impossible to predict how the virus will affect one individual to the next, who may have no symptoms, and who might become very, very ill."
To reduce your exposure to mosquitoes and reduce your risk of West Nile Virus, the Department of Human Resources recommends the following:
Use insect repellent containing DEET. Repellents with 35% DEET are effective for adults, while repellents with 10% DEET are usually recommended for children; do not use repellents on children younger than two months of age. Always read and follow the directions on the package when applying insect repellents.
If you will be camping or spending long periods of time where mosquitoes are generally present, Permanone may be sprayed on clothing. Permanone should not be used on the skin; read package instructions carefully.
Wear light-colored, weather and environment-appropriate clothing.
Empty standing water in and around your yard and home. Old tires, children’s toys, flower pots, uncovered boats, and uncovered garbage cans can all collect water and provide areas for mosquitoes to breed. Refresh water in outdoor pet dishes daily, and change the water in birdbaths every three to four days (twice weekly). Use larvicides in ponds or other sources of standing water that cannot be emptied.
Keep grass cut and hedges trimmed; make sure rain gutters are clean and free of leaves and other debris that can cause them to clog and hold water.
Limit outdoor activities at dusk and dawn when mosquitoes are most active, and avoid prolonged outdoor activities where large numbers of mosquitoes are generally present.