Scientific creativeness, discovery, and hard work produce the vaccines. The health community provides leadership in disseminating the news. Responsible parents assume the job of having their children vaccinated. And the cases tumble.
The data above are graphed on a logarithmic scale so that details at low incidence rates are still visible too. This form of presentation understates the great change that has taken place — shown in the small chart to the left (for measles) using ordinary scale. These diseases — affecting hundreds or tens of thousands of children, now affect two or three hundred — or none. Smallpox is not shown at all. It virtually disappeared before 1950. But in the area of health, it appears that victory should not be declared too soon or too confidently. Bacteria are resilient, and people sloppy.
As we point out in Chapter 3, Prevention, as of 1999, 4% of children were not immunized against diphtheria, 8% were not vaccinated against measles, and 10% were not protected from polio. But the interesting trend and indicator, shown in the graphic, is the "contrarian" movement of pertussis, whooping cough. After a period of long decline, cases of pertussis began to climb again after 1981 in a pattern that professionals refer to as the "reemergence" of the disease.
One of the important actors in the control of diseases is the virus or the bacterium that causes it. In Australia, Canada, and in The Netherlands — all countries with highly vaccinated populations — the disease has reemerged. A comprehensive study in The Netherlands (see Mooi in source), has shown that adaptations of the bacterium, Bordetella pertussis, have permitted it to increase its circulation in the population. Pertussis is an endemic disease, meaning that it is always present in the population. Vaccination had evidently reduced its prevalence but adaptation has allowed it to "expand" again and to infect more people. In the U.S. the growing incidence of the disease may have other causes — possibly other adaptations. It has increased substantially among adolescents and adults. No vaccines specific for these age groups have been developed. Thus the battle continues (see Todar in source).
A brief note about the diseases shown in the graphic. Diphtheria is an infection that attacks the respiratory tract. The bacterium, Corynebacterium diphtheriae, produces a toxin that can damage the nerves and the heart. Recovery is slow. Diphtheria is a serious disease —it has a 10% death rate.
A virus causes measles, also known as rubeola. After a person is vaccinated or has the disease, he or she becomes immune. People are feverish, cough, and have inflamed eyelids. Measles produces a rash. A serious complication of the disease — which happens in about 1 case out of 3000 — is encephalitis, an inflammation of the brain.
Mumps is another viral disease. It causes painful swelling of the salivary or parotid glands. Parotid glands are those located between the ear and the jaw and also produce saliva. This is a childhood disease (children 2 to 12) but can also affect adults. Those affected gain lifetime immunity.
Pertussis, whooping cough. The disease gets its common name because, during convulsive coughing, one of the symptoms of the disease, children make a sound as they breathe in. Severe cases of the disease, when left untreated, can have a poor outcome. About 1 to 2% of children die of the disease.
Polio, formally poliomyelitis, infantile paralysis, is a viral infection with variable outcomes depending on the form of the disease. Polio is classified into subclinical, nonparalytic, and paralytic types. Subclinical polio may produce no symptoms or relatively mild symptoms of discomfort, fever, headache, and sore throat for about three days. Nonparalytic polio lasts from one to two weeks, has symptoms similar to but more intense than the subclinical variety, and causes considerable muscular pain, stiffness, and rashes. Of greatest concern is paralytic polio. It can lead to death, usually because the patient cannot breathe. More usually, a permanent disability is more likely than death.
Rubella, also known as German measles, is another viral disease. It has relatively mild symptoms but, in some special cases, can lead to serious results. Rubella produces a rash. It is less contagious than measles. The same vaccine, MMR, is used to immunize children against measles, mumps and rubella — hence its name. Children have few symptoms. The most dangerous outcome is for babies born to unvaccinated mothers who have ru- bella during early pregnancy. About a quarter of such babies develop congenital rubella. The disease damages the embryo and can result in heart defects, which may be repairable later, and in nervous system problems which are not reversible.
Source: Centers for Disease Control and Prevention. Summary of notifiable diseases, United States, 1999. MMWR 1999 and earlier years. Kenneth Todar, "Bordetella pertussis and Whooping Cough." University of Wisconsin-Madison. Online. Available: http://www.bact.wise.educ/Bact330/lecturebpertussis. Frits R. Mooi, Inge H.M. van Loo, and Audre King, "Adaptation of Bordetella pertussis to Vaccination: A Cause for its Reemergence?" National Institute for Public Health and the Environment (RIVM) Bilthoven, The Netherlands, http://www.cdc.gov/ncidod/eid/vol7no3_supp/mooi.htm.
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