1. WEST NILE VIRUS By: Beverly M. Sorreta

2. FIRST WHAT IS A VIRUS? microscopic particle that can infect the cells of a biological organism. Viruses can only replicate themselves by infecting a host cell and therefore cannot reproduce on their own. microscopicinfectcellsorganism Viruses lie around our environment all of the time just waiting for a host cell to come along. They can enter us through the nose, mouth or breaks in the skin (see How the Immune System Works for details). Once inside, they find a host cell to infect. For example, cold and flu viruses will attack cells that line the respiratory or digestive tracts. The human immunodeficiency virus (HIV), which causes AIDS, attacks the T-cells of the immune system.How the Immune System Worksrespiratoryimmune system

4. The bacteriophage life cycle involves attachment, replication and release. Bacteriophage recognize a protein on the outside surface of the microbe, such as the flagella, a pilus, or a receptor for transport of a sugar. They bind this protein and inject their nucleic acid inside. Replication then begins inside the host cell. After replication, the virus leaves the host cell either by budding out of the host membrane, or by lysing the host cell.

5. WEST NILE VIRUS? West Nile virus is a virus of the family Flaviviridae, found in both tropical and temperate regions. It mainly infects birds, but is known to infect humans, horses, cats, bats, chipmunks, skunks, squirrels, and domestic rabbits. The main route of human infection is through the bite of an infected female mosquito.virusFlaviviridae tropicaltemperatebirdshumanshorsescatsbatschipmunksskunkssquirrelsrabbitsmosquito commonly found in Africa, West Asia, and the Middle East. It is closely related to St. Louis encephalitis virus which is also found in the United States. The virus can infect humans, birds, mosquitoes, horses and some other mammals The most severe type of disease due to a person being infected with West Nile virus is sometimes called “neuroinvasive disease” because it affects a person’s nervous system.

6. Less than 1 percent of people bitten by an infected mosquito come down with the most serious nervous-system conditions related to West Nile: West Nile encephalitis - inflammation of the brain West Nile meningitis - inflammation of the membrane surrounding the brain and the spinal cord West Nile meningoencephalitis - inflammation of the brain and surrounding membrane West Nile poliomyelitis - inflammation of the spinal cord These conditions occur when the virus is able to penetrate the blood- brain barrier and attack the brain and/or spinal cord. The immune system, in trying to fight off the infection, sends out chemical signals that cause inflammation. This inflammation can interrupt normal functioning of the brain and/or spinal cord.

9. SYMPTOMS In humans, the virus often causes only a mild infection -- characterized by fever, headache, tiredness, aches and rash -- that clears up without further treatment. But some patients develop severe infections resulting in neurological disease and even death. Symptoms of the most serious forms of West Nile virus can include: high fever stiff neck disorientation convulsions coma numbness paralysis

10. How do people get infected with West Nile virus (WNV)? The main route of human infection with West Nile virus is through the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. The virus eventually gets into the mosquito's salivary glands. During later blood meals (when mosquitoes bite), the virus may be injected into humans and animals, where it can multiply and possibly cause illness

11. Basic transmission cycle of WNV Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. Infected mosquitoes can then transmit West Nile virus to humans and animals while biting to take blood. The virus is located in the mosquito's salivary glands. During blood feeding, the virus may be injected into the animal or human, where it may multiply, possibly causing illness

13. HOW IS IT DIAGNOSED? VACCINE? The current standard for diagnosing is by testing blood or cerebrospinal fluid with the IgM antibody capture enzyme-linked immunosorbent assay (ELISA) abd IgG indirect ELISA There is no human vaccine for West Nile virus but a formalin-inactivated whole virus vaccine has been approved for use in horses

14. PREVENTION Eliminate standing water in your yard. Mosquitoes breed and multiply in pools of standing water. Unclog roof gutters. Empty unused swimming pools. Change water in birdbaths at least weekly. Remove old tires or any unused containers that might hold water and serve as a breeding ground for mosquitoes. Watch for sick or dying birds and report them to your local health department.

15. Avoid unnecessary outdoor activity when mosquitoes are most prevalent, such as at dawn, dusk and early evening. Wear long-sleeved shirts and long pants when you go into mosquito- infested areas. Apply mosquito repellent with a 10 percent to 30 percent concentration of DEET to your skin and clothing.

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