Introduction | What It Is and How It's Transmitted | Prevention | Humans and West Nile | Animals and West Nile | Research and Surveillance | Resources About West Nile Virus
Courtesy of www.redcross.org.
Since West Nile virus made its U.S. appearance in 1999, scientists have been working to find ways to protect humans and animals from infection.
Microbiologists and other scientists conduct basic and applied research to better understand the virus, environmental factors that influence disease emergence, and the disease in humans. They seek new tests to screen blood for West Nile virus and diagnose infected people, more targeted treatments, vaccines to prevent the disease in humans and animals, and better tracking and control methods for mosquitoes.
Efforts to develop and approve a test to screen donated blood have moved quickly following the discovery that West Nile infection could be acquired via blood transfusion. In July 2003, U.S. blood banks began using a new test that detects the genetic material of West Nile virus using nucleic acid amplification testing.
The test will not only reduce the risk of West Nile virus transmission by blood transfusions, but help public health officials monitor the extent of the disease. Data compiled from the blood screening process will be shared with public health departments, providing what the American Association of Blood Banks calls "unprecedented real-time surveillance" of human West Nile virus activity.
In July 2003, the U.S. Food and Drug Administration approved a clinical test to diagnose West Nile virus encephalitis. An estimated one in 100 to 150 people infected with the virus develop encephalitis or meningitis.
West Nile virus courtesy of NIAID.
Currently, the only vaccines against West Nile are for animals. An experimental vaccine has been widely used in horses since 2002. This vaccine has been used at some zoo and animal parks to protect a variety of animals.
Another experimental vaccine, which is based on recombinant DNA, has been used on endangered birds.
Development of a human vaccine has been under way since 1999. National Institute of Allergy and Infectious Diseases (NIAID) scientists have developed an experimental West Nile vaccine that has shown promise in monkeys.
The candidate vaccine, which uses a dengue virus as a backbone to carry West Nile virus genes, will be tested in Phase I clinical trials in humans in late 2003. Another experimental vaccine developed by the biotechnology company Acambis uses a similar approach with a yellow fever vaccine virus backbone. It has also shown promise in animal studies, and is expected to undergo initial clinical trials in humans in 2003.
Currently, there are no drugs to treat West Nile disease. Scientists believe, however, that drugs can be developed to treat the disease because infection is typically not chronic and because antiviral drugs have been found effective in lab experiments against related flaviviruses.
NIAID funds a project to develop novel therapeutic agents against West Nile virus. More than 550 drug candidates have been screened, with about 3% identified as showing promise for additional testing in animals. The institute has also established two research centers in New York and California to focus on West Nile and related viruses.
Tracking infection of humans, birds, and other animals is critical to learning more about the disease and how it spreads. Monitoring and surveillance allows scientists to develop and test strategies to control West Nile.
Microbiologist Chris Carlson prepares to examine a dead crow. Courtesy of South Dakota Public Health Laboratory.
To track and predict the spread of the virus, scientists rely on tools ranging from the everyday reporting of a dead crow or bird in your backyard to literally out-of-this-world techniques such as satellite imagery.
Here on earth, local public health officials collect or count dead crows and other birds affected by the virus, and track reports of infections in horses, other animals, and humans. They may also trap mosquitoes for testing to determine the prevalence of West Nile virus infection. Early detection of West Nile virus activity allows local health officials to rapidly implement emergency response plans and control mosquitoes.
Local and state public health departments share their data with with the Centers for Disease Control and Prevention (CDC), which provides real-time data on West Nile virus activity across the nation.
CDC publishes daily maps of West Nile activity in humans, animals and mosquitoes.
CDC's national electronic surveillance system called ArboNet helps states track West Nile and other mosquito-borne viruses. CDC also funds university programs that train postgraduate scientists in arbovirology and medical entomology to increase the number of scientists who know about diseases that are carried by mosquitoes and other vectors of infections.
Far above earth, NASA scientists collect and analyze temperature and vegetation data from satellites to help monitor and predict the spread of West Nile virus. Mosquitoes and birds that carry the virus thrive under specific environmental conditions. As temperature and precipitation levels change throughout the year, these conditions "migrate". Scientists and health officials combine public health data with satellite data to determine areas that might be at increased risk for West Nile virus.
NASA tracks land surface temperatures (left) and combines disease control data with satellite data to determine areas at risk for West Nile virus (right).
Controlling mosquitoes is critical to controlling West Nile virus. Because the virus can be transmitted from a female mosquito to her offspring, preventing mosquito eggs from hatching is especially important. Scientists are looking for environmentally sound ways to eliminate mosquitos.
The two most commonly used larvacides today are methoprene and Bacillus thuringiensis israelensis (BtI). A naturally occurring soil bacterium, BtI breaks down quickly and may require frequent treatments. Methoprene, first registered by the Environmental Protection Agency in 1975, mimics the action of a growth-regulating hormone in order to prevent maturation of mosquito larvae. Some scientists are concerned that mosquitoes may develop resistance to one or both pesticides.
Some scientists are working to develop biodegradable insecticides that will kill insect larvae. For example, Insect Biotechnology, Inc. has developed an insect hormone that turns off the digestive enzymes mosquitoes need to grow and develop.
Introduction | What It Is and How It's Transmitted | Prevention | Humans and West Nile | Animals and West Nile | Research and Surveillance | Resources About West Nile Virus
Oct. 8, 2003
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