NE507: Mosquitoes, Disease & Public Health
Statement of Issues and Justification
Infectious diseases are on the rise worldwide and account for a quarter of all human mortality and morbidity despite extraordinary medical advances. Diseases once thought to menace only remote tropical inhabitants are now spreading everywhere, fueled by international travel.The mosquito could be considered the most dangerous creature on earth. Diseases transmitted by mosquitoes have killed more people than all the wars in history. Each year there are 300 - 500 million cases of malaria reported, resulting in up to 2.7 million deaths, mostly children. By contrast, the AIDS virus afflicts <6 million people annually.
Arboviruses are the most significant cause of mosquito-borne disease in the U.S. Arboviral infections often result in encephalitis, a brain inflammation which can result in death or severe neurologic after-effects. U.S. mosquitoes transmit several serious endemic encephalitic viruses including St. Louis, LaCrosse, and eastern and western equine encephalitis. There are no vaccines, antibiotics, or treatments for viral encephalitis. Mitigation centers on controlling mosquitoes that transmit the diseases.
The introduction and rapid dispersal of mosquito-borne West Nile virus (WNV) has effectively demonstrated the infectious threat poised by arboviruses. WNV is merely the latest in a series of infectious viruses of national public health significance to be introduced into the United States. This virus swept across the country following its appearance in New York in 1999, and the disease is now endemic in the continental 48 states. The outbreak constituted the largest documented epidemic of mosquito-borne meningoencephalitis in the history of the western hemisphere. Although principally a disease of birds (explaining its swift dispersal), nearly 24,000 people in the U.S. have become infected with WNV with 900 deaths recorded to date. The elderly and children are at particular risk of developing serious illness.
The U.S. will continue to experience the arrival of new arboviral diseases. Consider chikungunya virus, a deadly infectious disease that causes crippling arthritic damage to survivors. The virus has infected more than 1.5 million people in the Indian Ocean region in a massive eruption over the past 24 months. Nearly a dozen U.S. states have reported cases of infected travelers returned from Asia and East Africa. Ultimately infectious patient will meet competent vector and the disease will undergo establishment, amplification, and dispersal. The U.S. not only is a travel and immigrant destination for large numbers of South Asians, but also has a highly competent vector -- Aedes albopictus. Or consider dengue, the predominant mosquito-borne viral disease affecting humans. The disease is now endemic in >100 countries and infects 100 million persons each year with 2.5 billion at risk. The World Health Organization has reported a 30-fold incidence increase in dengue over the past 50 years. Dengue reemerged in Hawaii in 2001; four cases were reported in Philadelphia this year. Although these viruses have been spread inadvertently, their introduction as agents of bioterrorism is a very real threat.
The economic impact of mosquito-borne illness is also devastating. The cost of treating WNV infections has been immense, with Louisiana estimating $70 million for 2002 alone. The estimated cost per human case of eastern equine encephalitis (EEE) is $3 million. EEE and WNV both threaten the nations multi-billion dollar equine industry. The mortality rate of horses infected with WNV is 34 percent; the rate for those with EEE is 100 percent. In 2000, the estimated loss in New Jersey due to equine cases of WNV was $6 million. Tourism, which increases human exposure to mosquitoes, is similarly impacted by outbreaks of mosquito-borne disease. This was effectively demonstrated in 1959 in New Jersey, when 21 people died during an EEE outbreak, resulting in tourism coming to a near standstill.
The lessons learned from WNV and the threat posed by additional new and emerging arboviruses serve as an impetus for bolstering U.S. vigilance against insect-borne diseases, particularly when we consider their potential to be used by terrorists. The U.S. requires research and outreach capabilities that provide answers to preventing and controlling outbreaks of arboviruses and other pathogens transmitted by mosquitoes.
Back to Top