Comparing West Nile, Malaria, Plague, and Yellow Fever

Introduction to Four Vector-Borne Diseases

This paper examines four significant infectious diseases: West Nile virus, malaria, plague, and yellow fever. It discusses the history and distribution of each disease in the United States and worldwide, and compares them based on their relative impact — including health, economic, and social consequences — to determine which is most significant individually and overall.

West Nile Virus: Rapid Spread and Growing Threat

West Nile virus only appeared in the United States in 1999, but it has become a widely feared disease since then. The virus is contracted by humans through infected mosquito bites, and it can be deadly in people with weakened immune systems, such as children and senior citizens. Symptoms of the disease can be minor, such as headaches and a low-grade fever, but can escalate to confusion, muscle weakness, high fever, and severe headache (Editors, 2004). Symptoms typically appear 3 to 14 days after a bite. More serious symptoms include brain swelling, coma, numbness, vision loss, and disorientation, though these are far less common. Some infected individuals show no symptoms at all. West Nile can kill those with weaker immune systems, and severe cases have a significant impact on individual health.

By 2002, the disease had "exploded" across the nation, and in 2003 it was detected in mosquitoes in every state in the 48 contiguous states except Oregon and Washington. According to the Centers for Disease Control and Prevention (CDC), there were 9,858 human cases of the disease in 2003 and 262 deaths — down slightly from 284 deaths in 2002 (Editors, 2004). This spread began from a single dead crow discovered in New York City in 1999. The virus is extremely common wherever mosquitoes breed and live, making it very difficult to control. It can also be transmitted through blood transfusion and from mother to unborn child.

There is no known cure for West Nile virus. For mild cases, people recover as the disease runs its course. The CDC was working on a vaccine at the time of writing but did not expect it to be ready for several years (Editors, 2004). For more severe cases, treatment often includes hospitalization with intravenous fluids, breathing assistance, and nursing care (Editors, 2004).

The economic impact of this disease has been substantial. Treatment costs are less of a concern than the heavy spraying of mosquito-infested areas in attempts to control the spread. Precise cost estimates for nationwide mosquito-spraying programs are unavailable, but the financial burden on many communities is considerable. The disease was on the rise in the United States and around the world, and researchers expected it to continue expanding. As one panel noted, "During 1999–2002, the virus extended its range throughout much of the eastern parts of the U.S.A., and its range within the western hemisphere is expected to continue to expand" (Campbell et al., 2002, p. 1).

The virus can infect a wide variety of animals, including birds, "horses, bats, chipmunks, skunks, squirrels, and even alligators" (Ward, 2003, p. B01), which facilitates its rapid spread across entire continents. Often, the host dies from the disease. The social impact is difficult to measure precisely, but outdoor activities are frequently curtailed during the months the disease is most active — June through October, peaking in September (Ward, 2003, p. B01). In areas prone to mosquitoes, residents are urged to stay indoors during these months or apply insect repellent containing DEET (N,N-diethyl-meta-toluamide). The CDC also recommends draining standing water around the home to reduce mosquito breeding sites. West Nile virus is particularly alarming because it can spread so quickly and is often difficult to detect early.

Malaria is a disease that has made a significant comeback worldwide. Once thought to be nearly eradicated, it has returned as a major threat — particularly in Africa — partly due to concerns about the environmental impact of pesticide use and mosquito-spraying programs. Like West Nile virus, malaria is contracted from the bites of infected mosquitoes, usually females. The mosquitoes acquire the disease from the blood of infected individuals they bite (Editors, 2004). One of the key challenges in controlling malaria is that mosquitoes have developed resistance to the malaria parasite, enabling them to transmit the disease without succumbing to it themselves (Tenenbaum, 2002, p. 760).

Malaria: A Resurgent Global Killer

The symptoms of malaria include alternating fever and chills. "Malaria may also cause renal or pulmonary failure; cerebral malaria, which usually afflicts children and pregnant women, can cause coma, generalized convulsions, and death" (Tenenbaum, 2002, p. 760). The most severe outcome is death, but what makes malaria especially dangerous is that it is often a silent disease. The malaria parasite can remain in a person's body for years without being detected. The CDC notes, "Two types of parasites have dormant liver stages that can remain silent for years. Left untreated, these liver stages may reactivate and cause malaria attacks ('relapses') after months or years without symptoms. Another type, if left untreated, has been known to persist in the blood of some persons for several decades" (Editors, 2004). The fear of undetected malaria — and the risk of unknowingly infecting others — represents a serious public health concern.

Although malaria was thought to have been eradicated in the United States for decades, there were 1,337 cases and eight deaths reported in the U.S. in 2002 (Editors, 2004). Globally, the picture is far more alarming. As one writer observed, "Today, malaria is resurgent in many tropical regions, especially Africa. According to the World Health Organization, each year it infects more than 300 million people and kills at least 1 million, mostly children" (Tenenbaum, 2002, p. 760). There is currently no vaccine against malaria, though the disease can be treated effectively if caught early. Travelers to malaria-endemic regions can take preventive medication, and health professionals should be consulted about the most appropriate drug regimen for each individual.

The economic impact of malaria is staggering given the sheer number of victims it claims every year. While many of the world's poor die at home from the disease, many more require hospitalization, with costs including treatment, medication, and blood transfusions. In addition, large expenditures go toward mosquito eradication programs. Ironically, the cost of medications themselves is quite low: the CDC notes that "the average cost for potentially life-saving treatments of malaria are estimated to be U.S.$0.13 for chloroquine, U.S.$0.14 for sulfadoxine-pyrimethamine, and U.S.$2.68 for a 7-day course of quinine" (Editors, 2004). Many developing countries, however, simply lack the resources to treat or eradicate the disease, and as a result their citizens — especially children — continue to die in large numbers.

The CDC reports that "in areas of Africa with high malaria transmission, an estimated 990,000 people died of malaria in 1995 — over 2,700 deaths per day, or 2 deaths per minute" (Editors, 2004). These figures are difficult to comprehend but illustrate that malaria remains one of the deadliest diseases on the planet. The disease can lie undetected for years and is a persistent killer. Its implications are clear: malaria must be controlled and eradicated urgently to prevent further loss of life.

The plague inspires widespread fear because of its historical association with the "Black Death" that swept through Europe in the 1300s, killing millions. Although the plague is far less prevalent today, its long and devastating history makes it one of the most psychologically frightening diseases in human memory. The most common form is the bubonic plague, contracted through the bites of infected fleas that live on rats or other rodents. It can also be transmitted through direct skin contact with infected tissue — for example, by handling a dead animal — or through droplets inhaled from the cough or sneeze of an infected person (the pneumonic form).