Infectious Diseases - Tuberculosis

Tuberculosis (TB), a communicable disease caused by the bacterium Mycobacterium tuberculosis, is spread from person to person through the inhalation of airborne TABLE 7.4 Pandemic flu planning checklist for individuals and families "Pandemic Flu Planning Checklist for Individuals and Families," in Planning Checklist, U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, January 12, 2006, http://www.pandemicflu.gov/plan/pdf/Individuals.pdf (accessed January 17, 2006)particles containing M. tuberculosis. The particles, called droplet nuclei, are produced when a person with infectious TB of the lungs or larynx forcefully exhales, such as when coughing, sneezing, speaking, or singing. These infectious particles can remain suspended in the air and may be inhaled by someone sharing the same air.

TABLE 7.4
Pandemic flu planning checklist for individuals and families
SOURSE: "Pandemic Flu Planning Checklist for Individuals and Families," in Planning Checklist, U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, January 12, 2006, http://www.pandemicflu.gov/plan/pdf/Individuals.pdf (accessed January 17, 2006)
1. To plan for a pandemic:
Store a supply of water and food. During a pandemic, if you cannot get to a store or if stores are out of supplies, it will be important for you to have extra supplies on hand. This can be useful in other types of emergencies, such as power outages and disasters. Ask your doctor and insurance company if you can get an extra supply of your regular prescription drugs. Have any nonprescription drugs and other health supplies on hand, including pain relievers, stomach remedies, cough and cold medicines, fluids with electrolytes and vitamins. Talk with family members and loved ones about how they would be cared for if they got sick, or what will be needed to care for them in your home. Volunteer with local groups to prepare and assist with emergency response. Get involved in your community as it works to prepare for an influenza pandemic.
2. To limit the spread of germs and prevent infection:
Teach your children to wash hands frequently with soap and water, and model the correct behavior. Teach your children to cover coughs and sneezes with tissues, and be sure to model that behavior. Teach your children to stay away from others as much as possible if they are sick Stay home from work and school if sick.
3. Items to have on hand for an extended stay at home:
Examples of food and non-perishables	Examples of medical, health, and emergency supplies
Ready-to-eat canned meats, fruits, vegetables, and soups Protein or fruit bars Dry cereal or granola Peanut butter or nuts Dried fruit Crackers Canned juices Bottled water Canned or jarred baby food and formula Pet food	Prescribed medical supplies such as glucose and blood-pressure monitoring equipment Soap and water, or alcohol-based hand wash Medicines for fever, such as acetaminophen or ibuprofen Thermometer Anti-diarrheal medication Vitamins Fluids with electrolytes Cleansing agent/soap Flashlight Batteries Portable radio Manual can opener Garbage bags Tissues, toilet paper, disposable diapers

Most TB (approximately 85%) occurs in the lungs (pulmonary TB). Risk of transmission is increased where ventilation is poor and when susceptible people share air for prolonged periods with a person who has untreated pulmonary TB. The disease, however, may occur at any site of the body, such as the larynx, the lymph nodes, the brain, the kidneys, or the bones. This type of TB infection, which occurs outside the lungs, is referred to as extrapulmonary. With the exception of laryngeal TB, people with extrapulmonary TB are usually not considered infectious to others.

TB does not develop in everyone infected with the bacteria. In the United States about 90% of infected people never show symptoms of TB. Nevertheless, 5% of people infected develop the disease in the first or second year after infection. Another 5% show symptoms later in life. For people with compromised immune systems, the risk of developing TB is much higher. For example, more than 10% of those infected with both TB and HIV (the virus that causes AIDS) develop full-blown TB symptoms within a year, according to Elizabeth L. Corbett et al in "The Growing Burden of Tuberculosis: Global Trends and Interactions with the HIV Epidemic" (Archives of Internal Medicine, vol. 163, no. 9, May 12, 2003).

Ancient Enemy and Continuing Threat

Each year, two million people worldwide die from TB, according to the WHO, and more than eight million people become sick with TB annually (http://www.who.int/mediacentre/factsheets/who104/en/print.html). Overall, one-third of the world's population is infected with the TB bacillus. This has increased dramatically since the HIV/AIDS epidemic swept through many countries. In 2000 the WHO estimated that at least five million adults worldwide—primarily in sub-Saharan Africa, Latin America, and Asia—had been infected with both AIDS and M. tuberculosis. Corbett et al report that TB accounts for 11% of deaths from AIDS worldwide.

After several decades of decline, TB made a comeback in the United States in the late 1980s and early 1990s. From 1985 to 1993 more than 64,000 new TB cases were reported. In 1992 the CDC reported 26,673 cases of TB, up from 22,201 in 1985. Since 1992 the number of cases has declined steadily, and by 2004 it had decreased to 14,517. (See Table 7.5.)

The decline in the total number of TB cases reported to the CDC is attributable to new public health programs that monitor the complicated drug-treatment protocols for patients with TB. The success of prevention and treatment programs varies depending on the location and population. Despite these overall national declines in TB incidence, substantial disparities exist between rates in the majority of U.S. residents and rates in two U.S. populations—foreign-born people and U.S.-born non-Hispanic African-Americans, both of which experience higher rates of TB. (See Table 7.6 and Figure 7.1.)

Treatment has become increasingly difficult because new strains of multidrug-resistant (MDR) TB have developed. If the disease is not properly treated or if treatment is not completed, some TB can become resistant to drugs, making it much harder to cure. According to the CDC, in 2003, the most recent year for which drug-susceptibility data were available, there were 114 cases of MDR TB, and it was more common in foreign-born people (1.2%) than in U.S.-born residents (0.6%; http://www.cdc.gov/od/oc/media/pressrel/fs050317.htm). The CDC also reports that in 2000, 80.8% of patients with TB completed therapy in one year or less, and 92.2% completed therapy overall.

The CDC reports in Emerging Infectious Diseases (Anthony S. Fauci, Nancy A. Touchette, Gregory K. Folkers, "Emerging Infectious Diseases: A 10-Year Perspective from the National Institute of Allergy and Infectious Diseases," vol. 11, no. 4, April 2005, http://www.cdc.gov/ncidod/eid/vol11no04/pdfs/04-1167.pdf) that researchers are using genomic (science that studies the structure and function of genes) techniques to identify key molecular pathways that could be used to develop improved TB treatments and vaccines. In 2004, for the first time in sixty years, clinical trials of two new vaccines designed to prevent TB began. Many promising new anti-TB drug candidates also are now entering the drug pipeline. Derivatives of known anti-TB drugs, such as thiolactomycin and ethambutol, are currently being screened for activity against Mycobacterium tuberculosis, and another new anti-TB drug, SQ109, is under development.

March 24 of each year has been designated "World TB Day" by the NIAID to recognize the global threat to health posed by the disease. If the disease is not controlled and treatment is not improved, it is estimated that between 2002 and 2020 approximately one billion people will be newly infected with TB, more than 150 million people will get sick from TB, and thirty-six million will die of TB, according to the WHO.