The Truth About West Nile Virus
- arthuroslund2
- Sep 19
- 3 min read
While communities have good intentions, many existing policies and programs may be dangerous to children, adults and wildlife and inadequate by relying too heavily on spraying pesticides to kill adult mosquitoes.
NOT ALL MOSQUITOES CARRY WEST NILE VIRUS
There are 175 different species of mosquitoes in the U.S. and only a handful of those are vectors for disease. Only adult female mosquitoes bite and require blood meals; males feed on flower nectar.
Mosquitoes go through four stages in their life cycles – egg, larva, pupa, and adult. The complete cycle can take as little as four days or as long as one month, depending on the temperature.
West Nile virus (WNv) and St. Louis encephalitis are primarily associated with the Culex mosquitoes.
Adult Culex females live between 2-4 weeks, depending on climate, species, predation, and a host of other factors. Culex mosquitoes are generally weak fliers and do not move far from their larval habitat, although they have been known to fly up to two miles. High bite rates usually indicate breeding areas are nearby.
Mosquitoes are most active at 80°F, become lethargic at 60°F, and cannot function below 50°F.
THE REAL THREAT OF WEST NILE VIRUS
Less than one percent of those infected with WNv will develop severe illness, according to the Centers for Disease Control. The vast majority of people (about 80%) who become infected with WNv will show no symptoms and never become sick. Some 20% may experience mild flu-like symptoms within 3 - 15 days.
Brian Rogers, D.O., MPH, City of Fort Worth Health Authority states, “The risk of becoming seriously ill and dying from West Nile is extremely minimal. Fewer than 1 percent of mosquitoes in areas where the virus has been found actually carry the virus.”
The U.S. Fish and Wildlife Services states, “Contrary to media descriptions of 'the deadly West Nile virus,' [it] is rarely fatal in humans. Less than one percent of people who acquire the disease will experience severe illness. Within this small proportion, the fatality rate is about 3-15%.”
Risk for severe illness is most closely correlated with increasing age and a weakened immune system. From 2001 to 2003 there was a drop in the average age of WNv cases (which include flu-like symptoms), however the median age of fatal cases has not dropped. The rise in cases in younger people is probably due to the heightened detection of milder WNv cases.
A person who has been infected with WNv may have life-long immunity even if they show no symptoms
Among all people who become infected with West Nile virus, most have mild symptoms that do not get reported. Typically, less than 1% will actually develop severe neuroinvasive disease, according to the CDC.
Reference
Aedes species
Readily and aggressively feeds on humans any time of the day. Has a short flight range - generally 1/2 mile or less. A main identifying feature are the striped legs. Aedes species are generally container breeders, laying their eggs above the water line on the inside of tires, buckets, planters, etc. When the water level rises, as after a rain, the eggs will hatch and the larvae begin their life cycle.
Culex species
All three of the Culex species can carry West Nile Virus breed in artificial containers and in water that is polluted with organic matter, such as septic effluent. They do not fly very far, having a flight range of about 1/2 mile. Breeding sites such as ornamental ponds, tires, and unused swimming and wading pools pose a significant threat, as do malfunctioning septic systems. Sites such as these will be primary contributors to large Culex populations.
Reference
Window screening, mosquito netting and repellent are some effective ways to keep from being bitten. Mosquitoes typically come out at dawn and dusk. When dragonflies are present, they protect us from all species of mosquitoes all the time.
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