Emerging Infectious Diseases are diseases that are new, re-emerging, or drug-resistant and the incidence in humans has increased within the past two decades or whose incidence threatens to increase in the near future. Factors that contribute to the emergence of new infectious diseases are microbial adaptation and change, widespread usage of antibiotics, economic development and land use, international travel and commerce, human demographics and behavior, and technology and industry. One emerging infectious disease that has been re-emerging is the West Nile Virus.
Disease and Pathology
West Nile virus is an emerging infectious disease because it keeps re-emerging; showing an increase in incidence and it has spread to different geographic areas by modern transportation. This virus was first identified in 1937 in Uganda, Africa and it has existed in Africa and the Middle East for decades, if not centuries. But in 1999, it landed in Queens, New York, via an unknown route. The infection then proceeded to move across the country and since then has spread to 48 states, Canada, Mexico, and many other countries.
Encephalitis is a severe symptom and the most common symptom in hospitalized West Nile Virus patients, affecting 50% to 84% of patients; it manifests with behavioral or personality changes such as irritability, confusion, or disorientation that can evolve into stupor and even a coma, with mental status changes persisting for up to several weeks. Although very serious symptoms rarely occur in infected people, about 20% of infected people do have milder symptoms, which include, fever, headache, body aches, nausea, vomiting and sometimes swollen lymph glands. The majority (80%) of infected people have no symptoms. Symptoms of West Nile fever will generally last a few days, although even some healthy people report having the illness last for several weeks, so it is an acute infection. The symptoms of severe disease (encephalitis or meningitis) may last several weeks, although neurological effects may be permanent. Complications from mild West Nile virus infection are very rare, but complications from severe West Nile virus infection include brain damage, permanent muscle weakness, and death. West Nile Virus has more severe long-term sequelae in older people than in younger people. These sequelae may be attributed to the severity of the patients' West Nile Virus infection, general effects of hospitalization, or the aging process itself.
Once a patient is infected, the virus multiplies in the tissues and lymph nodes near the site of entry, moves to the blood via lymphatics, infects the central nervous system, and becomes localized in the CNS. 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. Specific types of neuroinvasive disease include: West Nile encephalitis, West Nile meningitis, and West Nile poliomyelitis....