Displayed in the chart on the previous page are those countries with the highest TB rates per 100,000 people15. The United States was added to the chart for comparison. Excluding the United States, the only country in the chart to see a drop in the TB rate was the Democratic Republic of the Congo. Surprising, since all other African countries on the list saw their TB rates increase. In 2001, the WHO warned that TB cases in Africa were expected to double by 2010, partially due to the rise in HIV-positive cases. The chart bears this out. Between 24% and 67% of the TB cases in the African countries shown were also HIV-positive. South Africa's rate, for example, more than doubled from 1996 to 2000. By 2000, 60% of its TB cases also were HIV-positive.
This contrasted sharply with most of the other countries in the chart — where the percentage of TB with HIV-positive cases were between 0% and 1.4%. This suggests that other factors caused the numbers of TB cases to increase. Another factor could be the higher incidences of multidrug-resistant (MDR) TB. MDR TB may be more difficult to cure and may spread more rapidly if not treated promptly. In many of the non-African nations, more than 2% of their TB cases are MDR. In Afghanistan, for example, 7.3% of TB cases are MDR. Other factors contributing to the rise in TB rates are poverty (and associated poor health conditions), war (impeding the access to health care), and under- funding of health care programs.
Although the number of active TB cases in the United States has declined in the past nine years to just under 16,000, TB still remains a health threat. NIAID estimates that in 2002 10 to 15 million people in the U.S. are infected with TB. About 10% of them will develop an active case in their lifetime.
Why are so many infected and why is there an increasing risk of active cases developing? One reason is the HIV/AIDS epidemic. Those with HIV or AIDS have impaired immune systems which leaves them susceptible to developing an active case of the disease. Another reason is the number of foreign-born people living in the U.S. who come from areas where there is a high incidence of TB. About half of the TB cases are in this population. Poverty, injection drug use, and homelessness leave people susceptible to the disease. Crowded shelters and prisons have high incidences of TB transmission. As the population ages, health declines, and more people move into long-term care facilities. Those infected with the disease long ago are more likely to develop active cases and are more likely to spread the disease to others.
How does the U.S. compare to other North American and European countries? The table on the next page shows that in 2000, the U.S. rate was lower than many rates in other industrialized countries — quite an improvement since 1900, when the U.S. rate was 194 per 100,000 people.
TB Rates per 100,000 People for Selected North American and European Countries, 2000
| Hungary | 31.0 |
| Mexico | 16.0 |
| Germany | 11.0 |
| France | 10.0 |
| United Kingdom | 10.0 |
| Canada17 | 6.2 |
| Italy | 6.0 |
| United States | 5.8 |
| Sweden | 5.0 |
Sources: World Health Organization. Global Tuberculosis Control: WHO Report, 1998, 2001, and 2002. Retrieved July 11, 2002 from http://www.who.int. Division of Tuberculosis Elimination. Centers for Disease Control and Prevention . Reported Tuberculosis in the United States, 2000. Retrieved July 9, 2002 from http://www.cdc.gov. Howard Njoo, et. al. Health Canada. Tuberculosis in Canada-1996, 1998. National Institute of Allergy and Infectious Diseases. "Focus on Tuberculosis: Ancient Enemy, Present Threat." Retrieved July 8, 2002 from http://www.niaid.nih.gov/newsroom/focuson/tb02/tb.htm. World Health Organization. "HIV Causing Tuberculosis Cases to Double in Africa," April 23, 2001. Retrieved July 9, 2002 from http://www.who.int. World Health Organization. "Fact Sheet 104: Tuberculosis," April 2000. Retrieved July 8, 2002 from http://www.who.int. Centers for Disease Control and Prevention. "Achievements in Public Health, 1900-1999: Control of Infectious Diseases." Morbidity and Mortality Weekly Review, July 30, 1999. Retrieved July 3, 2002 from http://www.cdc.gov/mmwr/preview/mmwrhtml/mm4829a1.htm. National Institute of Allergy and Infectious Diseases. National Institutes of Health. "Fact Sheet: Tuberculosis," March 2002. Retrieved July 15, 2002 from http://www.niaid.nih.gov/factsheet/tb.htm.
1 Source: "Empedocles (fl. 450 BCE.)" The Internet Encyclopedia of Philosophy. Retrieved July 16, 2002 from http://www.utm.edu/research/iep/e/empedocl.htm.
2 The nutrients in a body of water increase, which leads to a reduction in the amount of oxygen in the water. As a result, fish, animal, and plant life are adversely affected.
3 1980-1994 asthma prevalence rate is based on 1970 population. The rate from 1995-1999 is based on 2000 population. Data from 1981-1994 were reported in 3-year intervals. The percentage of people with asthma went from 3% in 1980 to 5.5% in 1996.
4 Source: CDC.
5 An estuary is a body of water formed along the coast when fresh water from rivers flows into and mixes with salt water from the ocean. Estuaries provide an essential habitat for more than 75% of commercial fishing in the U.S. Some famous estuaries: Chesapeake Bay and Puget Sound. Source: "What is an Estuary?" Retrieved June 26, 2002 from http://www.estuaries.org/estuarywhat.html.
6 Nitrates are found in sewage and fertilizers and phosphates are found in detergents and fertilizers.
7 See the panel entitled "Air Pollution" for more information on the health affects associated with lead.
8 Cadmium accumulates in the kidneys and at very high levels can cause kidney failure. The average human daily intake of cadmium is 10 to 25 micrograms per day, far below the tolerable level of 60 to 70 micrograms per day recommended by the World Heath Organization. Source: http://www.cadmium.org.
9 Cholera is an illness caused by a bacterial infection of the intestine. Outbreaks in the U.S. are limited to travelers who were exposed to the disease in Asia, Africa, or Latin America and those that eat infected seafood they brought back to the U.S. Schistosomiasis is caused by parasitic worms that penetrate the skin. An estimated 200 million people are infected worldwide; however, the disease is not found in the U.S.
10 Plasmids (small, independently replicating DNA) with the resistant gene become incorporated into the genome of the other bacteria.
11 51% of counterfeit drugs uncovered by the World Health Organization contained no active ingredient. 17% contained the wrong ingredient. 11% contained weaker than the recommended concentration of the active ingredient. And some actually contained poisons that could lead to severe disability and death. Only 4% of counterfeit drugs contained the same quantity and quality of the drug as the legal equivalent. Source: World Health Organization.
12 Causes diarrhea, abdominal pain, and fever that may last 2-5 days. In people with suppressed immune systems, it can lead to a potentially fatal blood infection.
13 A quote by Lester Crawford, acting director of the FDA.
14 A quote by Senator Bill Frist of Tennessee at a Senate subcommittee hearing on public health.
15 The 1996 data for Zimbabwe, Cambodia, Kenya, and Mozambique are actually for 1999. These countries were selected from a list of the top 22 countries with the highest number of TB cases. These 22 countries account for 79.1% of the TB cases worldwide.
16 Ranked 10 in the number of TB cases in 2000. This rate is from the Country Profile section of the report Global Tuberculosis Control: WHO Report 2002. In the same report, the European regional section states the rate for Russian Federation as 95.
17 The most recent year available was 1996.
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