WASHINGTON — The incidence of tetanus has declined precipitously in recent decades, as have deaths from the toxin, but the elderly, diabetics, and injection-drug users are still at risk, according to research presented at the National Immunization Conference, sponsored by the Centers for Disease Control and Prevention.
Pamela Srivastava of the CDC's National Immunization Program, reported the results of an epidemiologic look at tetanus from 1972 to 2001. During that period, 1,842 cases of tetanus were reported to the CDC, Ms. Srivastava said.
Tetanus occurs from exposure to Clostridium tetani, a bacterium that releases a toxin initially causing headache, fever, sore throat, muscle spasms, and stiffness in the neck, arms, and legs. Left unchecked, the toxin will spread and lead to the characteristic “lockjaw,” as well as rigidity of other muscles. C. tetani can live for years in soil and feces. Infection usually comes through wounds. Historically, tetanus occurred more frequently in the southeast, and primarily in the summer, but most regional differences have disappeared, and there is not as much seasonal variation, either, she said.
The incidence of the infection has been on the decline in the United States, dropping 59% from 1972 to 2001. During that time, the case fatality rate decreased by 64%, she said.
Vaccination history was reported for 932 of the 1,842 cases. Among those, 644 (49%) were unvaccinated, and the case death rate was 28%. Among the 172 (18%) who had received one or two doses of vaccine, the death rate was 17%. Among the 114 persons (12%) who had received three or more doses, the death rate was 4%.
The number of cases and death rates were highest among people aged 60 or older, in whom the incidence was 0.78 per million and the death rate was 40%. She hypothesized that there was a low prevalence of immunity and high incidence of tetanus in the elderly, at least early in the study period, because they more likely had not received a primary immunization series. The incidence in the elderly declined some from 1991 to 2001.
Patients with diabetes were at increased risk for dying from tetanus. From 1987 to 2001, diabetic patients accounted for 13% of all cases and 29% of all deaths. Of the diabetics with tetanus, 44% died, Ms. Srivastava said.
There may be more people at risk, because a surprising number of tetanus cases come from nonacute, or chronic wounds, she said. About 16% of all the cases reported were from nonacute wounds; 76% were from acute wounds, and the rest from other sources.
Tetanus also has been steadily increasing over the decades in injection drug users. From 1992 to 2001, there was a threefold increase from previous decades, driven partly by an epidemic among users in California. During that decade, they accounted for 12% of all adult cases, Ms. Srivastava said.
Tetanus is not a high-cost disease in this country, costing only about $12 million a year, but it is severely disabling, and 78% of those affected are hospitalized. That argues for making sure vaccinations are up to date, she said.