West Nile encephalitis

West Nile fever is an infection by the West Nile virus, which is typically spread by mosquitoes. In about 80% of infections people have few or no symptoms. About 20% of people develop a fever, headache, vomiting, or a rash. In less than 1% of people, encephalitis or meningitis occurs, with associated neck stiffness, confusion, or seizures. Recovery may take weeks to months. The risk of death among those in whom the nervous system is affected is about 10%.A carbon dioxide-baited CDC light trap at NPSmonitoring site: The highest individual light trap total for 2010 was from a trap located in a salt marsh in the Fire Island National Seashore: around 25,142 mosquitoes were collected during a 16-hour period on August 31.Eggs of permanent water mosquitoes can hatch, and the larvae survive, in only a few ounces of water. Less than half the amount that may collect in a discarded coffee cup. Floodwater species lay their eggs on wet soil or other moist surfaces. Hatch time is variable for both types; under favorable circumstances (such as warm weather), the eggs of some species may hatch in as few as 1–3 days after being laid.Used tires often hold stagnant water and are a breeding ground for many species of mosquitoes. Some species such as the Asian tiger mosquito prefer manmade containers, such as tires, in which to lay their eggs. The rapid spread of this aggressive daytime feeding species beyond their native range has been attributed to the used tire trade. West Nile fever is an infection by the West Nile virus, which is typically spread by mosquitoes. In about 80% of infections people have few or no symptoms. About 20% of people develop a fever, headache, vomiting, or a rash. In less than 1% of people, encephalitis or meningitis occurs, with associated neck stiffness, confusion, or seizures. Recovery may take weeks to months. The risk of death among those in whom the nervous system is affected is about 10%. West Nile virus (WNV) is usually spread by infected mosquitoes. Mosquitoes become infected when they feed on infected birds, which often carry the disease. Rarely the virus is spread through blood transfusions, organ transplants, or from mother to baby during pregnancy, delivery, or breastfeeding. It otherwise does not spread directly between people. Risks for severe disease include being over 60 years old and having other health problems. Diagnosis is typically based on symptoms and blood tests. There is no human vaccine. The best way to reduce the risk of infection is to avoid mosquito bites. Mosquito populations may be reduced by eliminating standing pools of water, such as in old tires, buckets, gutters, and swimming pools. When mosquitoes cannot be avoided, mosquito repellent, window screens, and mosquito nets reduce the likelihood of being bitten. There is no specific treatment for the disease; pain medications may reduce symptoms. The virus was discovered in Uganda in 1937, and was first detected in North America in 1999. WNV has occurred in Europe, Africa, Asia, Australia, and North America. In the United States thousands of cases are reported a year, with most occurring in August and September. It can occur in outbreaks of disease. Severe disease may also occur in horses, for which a vaccine is available. A surveillance system in birds is useful for early detection of a potential human outbreak. About 80% of those infected with West Nile virus (WNV) show no symptoms and go unreported. About 20% of infected people develop symptoms. These vary in severity, and begin 3 to 14 days after being bitten. Most people with mild symptoms of WNV recover completely, though fatigue and weakness may last for weeks or months. Symptoms may range from mild, such as fever, to severe, such as paralysis and meningitis. A severe infection can last weeks and can, rarely, cause permanent brain damage. Death may ensue if the central nervous system is affected. Medical conditions such as cancer and diabetes, and age over 60 years, increase the risk of developing severe symptoms.