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Jun 18, 2006
West Nile Virus
by SirGan
 West Nile virus is one specific virus that is causing mosquito-borne illness that mainly affects birds, humans and horses. It is being transmitted through mosquito bites! There is no specific treatment for West Nile Virus infection or vaccine to prevent it. This condition is very strange because most people with West Nile virus have no symptoms and never know that they've been infected while others, especially older people or people with underlying medical conditions, can develop very serious condition which is leading to inflammation of the brain or inflammation and infection of the membranes surrounding the brain and spinal cord. West Nile Virus has spread rapidly across North America, affecting thousands of birds, horses, and humans, since it was discovered in the Western hemisphere. It is unknown whether West Nile encephalitis will present a serious health risk to the United States in the future.Incidence and spreadingAccording to the U.S. Centers for Disease Control and Prevention (CDC), over 15,000 people in the U.S. have tested positive for WNV infection since 1999, including over 500 deaths. Many more people have likely been infected with WNV, but have experienced mild or no symptoms.
The West Nile virus was first detected in the Western Hemisphere in 1999 and has since rapidly spread across the North American continent into all 48 continental states, seven Canadian provinces, and throughout Mexico. In addition, WNV activity has been detected in Puerto Rico, the Dominican Republic, Jamaica, Guadeloupe and El Salvador.
Transmission of the virusWest Nile Virus is transmitted to humans only through mosquito bites. Mosquitoes become infected when they feed on infected birds that have high levels of this virus in their blood. Infected mosquitoes can then transmit the virus when they feed on humans or other animals. Important fact is that West Nile Virus is not contagious from person to person and there is no evidence that a person can get infected by handling live or dead infected birds.
Symptoms of West Nile feverAlthough most people experience no symptoms what so ever, still, there are some symptoms that could be considered typical for the West Nile fever! Common signs and symptoms of West Nile fever include:
In less than 1 percent of infected people, the virus causes a more serious neurological infection, such as:
Signs and symptoms of these diseases also include:
Mechanism of the conditionThe real truth is that the exact mechanism of the disease is simply unknown! And although the mechanism is unknown, most experts from this field believe that the West Nile virus probably enters the host's bloodstream, multiplies and moves on to the brain, crossing the blood-brain barrier. What happens then? Once the virus crosses that barrier and infects the brain, an inflammatory response occurs and symptoms arise.
When all this happen? Well, several researches done in the past have showed that this virus transmission occurs mostly during warm weather, when mosquito populations are active. The incubation period ranges from 3 to 14 days.
In rare cases, it can be spread through other routes, including:
Although most people don’t know anything about this, it is a fact that some people have developed West Nile virus after receiving a transplanted organ or blood products. Although donated organs are not yet screened for West Nile virus, blood donor screening for West Nile was the routine now.
There is no doubt- congenital infection is possible! In 2002 in New York, a woman in her last trimester of pregnancy contracted West Nile virus and her baby was born five weeks later was also infected with West Nile virus!.
Infection via breastfeeding is possible but experts at the Centers for Disease Control and Prevention claim that such cases are extremely rare and should not affect any woman's decision to breast-feed her baby.
Some laboratory workers involved in West Nile surveillance and research have contracted the disease from infected animals.
Risk factors for developing West Nile feverOverall risk of contracting West Nile virus depends on several factors:
Several researches done in the past have came to the one conclusion- West Nile virus follows a seasonal pattern that begins in late spring, with the peak time for infection occurring in late summer and early fall.
People should know that every visit to the country where mosquito-borne viruses are common, especially the East Coast and Midwest, increases risk of West Nile virus.
If person work somewhere outdoors, logically he or she has a greater chance of being bitten by an infected mosquito.
The course of the disease could vary significantly. Some recover in two weeks and some develop really serious health problems. Among those more likely to develop severe or fatal infections are:
Diagnosis of West Nile Virus infectionThe fact is that anyone who has symptoms of severe illness such as mental status changes, high fever, neck stiffness, sensitivity to light, or confusion should go to the hospital's emergency department immediately.
Diagnosis of West Nile Infection isn't so complicated! Diagnosing West Nile virus infections is generally done through a combination of observing signs and symptoms along with specialized molecular biologic testing for the virus itself. Doctor can confirm the presence of West Nile virus in patient’s body by analyzing a sample of blood or the cerebrospinal fluid. Signs of the disease include:
Confirmatory diagnosis of West Nile virus infection is also done by a DNA test called polymerase chain reaction (PCR) or viral culture of fluid around the spinal cord.
Other tests:
The most common way to diagnose meningitis, as one of the possible complications of West Nile Virus infection, is to analyze the cerebrospinal fluid surrounding brain and spinal cord. A needle inserted between the lower vertebrae of your spine is used to extract a sample of fluid for laboratory analysis.
In some, but not all, cases, a computerized tomography (CT) or magnetic resonance imaging (MRI) scan can reveal brain inflammation and swelling.
The bottom line is that the most accurate way to diagnose this infection is serology, a test to detect the presence of antibodies against West Nile virus in CSF or serum. This is considered the gold standard for diagnosis.
Treatment of West Nile feverGood thing about all this is that most people recover from West Nile virus without treatment.
Prevention of infectionThis is not only the problem of an individual but the state problem! Efforts to detect and contain the virus include:
What can an individual do to reduce the risk of the infection? Well, there are some tips that showed beneficial:
There are also several other prevention measures! Some of those are:
Vaccine
Unfortunately- a vaccine is available to protect horses from West Nile virus but no vaccine is yet available for humans.
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