Infectious Disease

Illness caused by microbes, or germs, including viruses, bacteria, and certain multicellular organisms. New and reemerging infectious diseases pose a rising global health threat and will complicate U.S. and global security in the coming years. These diseases endanger U.S. citizens at home and abroad, threaten U.S. armed forces deployed overseas, and exacerbate social and political instability in key countries and regions in which the United States has significant interests.

Infectious diseases are a leading cause of death, accounting for one-quarter to one-third of the estimated 55 million deaths worldwide in 2002. The spread of infectious disease results from human behavior—changing lifestyles and land-use patterns, increased trade and travel, and inappropriate use of antibiotic drugs—as well as from mutations in microbes.

In the past 30 years, 20 previously well-known diseases, including tuberculosis (TB), malaria, and cholera, have reemerged or spread into new geographic areas, often in more virulent and drug-resistant forms. During the same time period, at least 30 previously unknown disease agents have been identified, including HIV, Ebola, hepatitis C, West Nile virus, and hantavirus, for which no cures are available.

Four of the seven biggest killers worldwide—TB, malaria, hepatitis, and, in particular, HIV/AIDS—continue to spread. They are also increasingly becoming resistant to drugs, making treatment ever less successful. HIV/AIDS and TB are likely to account for the overwhelming majority of deaths from infectious diseases in developing countries by 2020. The other major killers—acute lower-respiratory infections such as pneumonia and influenza, diarrheal diseases, and measles—appear to have stabilized in most areas, although the infection rate remains high.

The risk from infectious disease remains comparatively low in the United States, but diseases originating outside U.S. borders are often introduced by international travelers, immigrants, returning U.S. military personnel, or imported animals and foodstuffs. West Nile virus is an example of a disease that originated outside the United States and within a few short years of its introduction has become endemic in large parts of the country.

The threat from a previously unknown pathogen remains very real in the United States. In addition, HIV/AIDS, hepatitis C, TB, and new, more lethal variants of influenza are threatening or continue to threaten larger segments of the population. Hospital-acquired infections and foodborne illnesses also pose a danger. A risk from bioterrorism also exists, as shown by the anthrax attacks following the September 11 terrorist attacks.

Development of an effective global surveillance and response system to detect infectious disease is probably at least a decade away. Reasons for this delay include inadequate coordination and funding at the international level and lack of capacity, funds, and commitment in many developing and former communist states. Although overall global health care capacity has improved substantially in recent decades, the gap between rich and poor countries in the availability and quality of health care continues to widen.

The relationship between disease and political instability is indirect but real. A persistent infectious-disease burden aggravates and, in some cases, may even provoke economic decay, social fragmentation, and political destabilization. These effects are of particular concern in developing nations that have been hardest hit by the increase in infectious disease, especially HIV/AIDS, and in some of the former communist countries.

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