Infectious Diseases

by Food and Drug Administration (FDA)

In the late 1960s, after seeing such deadly diseases as smallpox, polio, and rheumatic fever get tamed by vaccines or antibiotics, Surgeon General William H. Stewart declared that it was time to close the book on infectious diseases and pay more attention to chronic ailments such as cancer and heart disease.

This commonly held belief that the war on infectious diseases could be won has been shattered by a score of new or reemerging diseases that have surfaced in epidemics scattered across the globe over the last 15 years, with some occurring within just the last year or two.

The new epidemics, combined with a deeper understanding of disease dynamics and the tricks microbes have up their sleeves, have shaken the medical community and led to a less rosy outlook. An article in the Jan. 17, 1996, issue of the Journal of the American Medical Association reported that infectious disease is now the third leading cause of death, after heart disease and cancer. Deaths from infectious disease rose 58 percent between 1980 and 1992, according to the article by Robert W. Pinner, M.D., of the national Centers for Disease Control and Prevention, and colleagues. Most of the increase is from AIDS cases. Yet even without AIDS cases, the death rate from infectious diseases rose 22 percent.

Some infectious disease experts wager future epidemics will take a greater toll on human life than those in the past, despite medical advances made over the past century. We are increasingly more vulnerable to infectious diseases, these experts point out, because of the growing proportion of people residing in urban areas, which act as magnets for epidemics. In 1800, less than 2 percent of the world's population lived in urban communities. By the year 2000, however, that fraction is expected to rise to 50 percent, according to the National Academy of Sciences.

Air travel, in addition, allows diseases to spread between cities on opposite ends of the globe in a matter of hours.

Prominent on the list of new or reemerging diseases that have health officials concerned are invasive strep infections, tuberculosis (TB), hantavirus pulmonary syndrome, malaria, and dengue. The Food and Drug Administration is responsible for insuring the safety and effectiveness of the drugs and vaccines used to curb infectious diseases.

Deadly Strep

Changes in the Streptococcus bacterium that give it more punch are credited with causing recent outbreaks of "flesh-eating" strep and streptococcal toxic shock syndrome (strep TSS). The latter disorder killed puppeteer Jim Henson in 1990.

Both these infections are caused by invasive strep — a type of Streptococcus that more readily spreads in the body than the types that cause strep throat. Studies by Dennis Stevens at the Veterans Affairs Medical Center in Boise, Idaho, suggest invasive strep is armed with two powerful toxins. In the body's furious attempt to rid itself of one of the toxins, the immune system can foster the destruction of infected muscle tissue or the sheath that covers the muscle (the flesh-eating manifestation) or prompt the body to go into shock, which is often fatal, or both. Damage also is wreaked by the other toxin, an enzyme that destroys tissue by breaking down protein.

Invasive strep usually enters the body through minor injuries, such as deep bruises, punctures, or chicken pox blisters. Only rarely is the deadly form of strep acquired through person-to-person contact. People with invasive strep usually don't complain of a sore throat, but rather often have flu-like achiness and fatigue that is followed by a number of symptoms, including pain in one region of the body, cough and difficulty breathing, or painful skin that is red, hot and swollen and gradually purples and forms blisters. This can be accompanied or followed by confusion, low blood pressure, and coma.

The antibiotics penicillin, erythromycin and clindamycin are the drugs of choice for treating invasive strep infections; the earlier treatment is begun, the better the outcome. Surgical removal of infected tissue, possibly including limb amputation, may be necessary. Researchers are currently testing a vaccine for invasive strep.

CDC estimates that about 15,000 cases of invasive strep infections occur each year in the United States, and studies by Stevens and others suggest one out of three people with invasive strep die. The infection can kill in less than a week.

Like most diseases, invasive strep is not new; China experienced an epidemic of flesh-eating strep in 1924, and strep infections were a major cause of death in Chicago and other cities in this country in the middle of the 19th century. It's not known for certain whether invasive strep currently is on the rise in this country. At this point, however, it is still considered a rare disease.

Tuberculosis

After a comforting steady decline since the 1950s, TB incidence in the United States began to climb in 1985, setting off alarms in the medical community. According to CDC, in 1994 there were 24,361 cases of TB in the United States — about 2,000 more cases than in 1984.

TB's comeback in this country is tied to the rising numbers of people whose immune systems are weakened by HIV infection, cancer and chemotherapy, or the drugs taken following an organ transplant. A resurgence of the disease is also being fostered by increasing poverty and drug abuse, as well as by increasing numbers of immigrants to this country with TB.

Well-known to the ancient Egyptians, TB is caused by airborne bacteria expelled from the lungs when a person with active TB coughs, sneezes or speaks. Repeated exposure to these droplets can infect another person's lungs.

The immune defenses of healthy people usually prevent TB infection from spreading beyond a small area of the lungs by creating a barricade around the bacteria. This walled-up infection is called latent TB and may be present throughout a person's life. People with latent TB test positive on the TB skin test. About 10 to 15 million people in this country have latent TB.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.