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Although rare, tetanus is still a life-threatening disease in the U.S., largely because of inadequate vaccination and wound care prophylaxis, CDC researchers said.

The majority of patients developed the disease as a result of an acute wound, but only about a third of them sought medical care, according to Tejpratap Tiwari, MD, of the CDC, and colleagues.

And even when they did, over 96% didn't receive appropriate prophylaxis, they reported in Morbidity and Mortality Weekly Report.

These factors may have contributed to an overall fatality rate of about 13%, which Tiwari said is still high although it has fallen significantly over the last century.

"Inadequate tetanus toxoid vaccination and inadequate wound prophylaxis remain the most important factors associated with tetanus," he and colleagues wrote.

Clostridium tetani, a spore-forming, Gram-positive bacillus, is ubiquitous in the environment, found in soil and animal excrement.

In the U.S., tetanus cases have been on the decline since the turn of the 20th century, largely due to use of tetanus antitoxin for wound management. Numbers have fallen even more significantly since 1947, the first year of national reporting, because of the introduction of tetanus vaccination in the 1930s and 1940s.

Since that year, cases have declined more than 95% and deaths fell more than 99%.

To monitor tetanus infection during the past decade, the researchers looked at reports from the National Notifiable Diseases Surveillance System (NNDSS) between 2001 and 2008.

They found a total of 233 cases of tetanus during that time.

Outcomes data were available for 197 cases, and, among those, the fatality rate was 13.2%.

The risk of death was highest among patients ages 65 and up (OR 9.6, 95% CI 3.6 to 25.0).

The vast majority of tetanus cases -- 71.7% -- had an acute wound before disease onset. Nearly 80% of these wounds were punctures, or were contaminated, infected, or devitalized wounds that were considered tetanus prone.

However, only 36.5% of these patients sought medical care -- and even when they did, just over 96% didn't receive the appropriate prophylaxis to prevent tetanus infection.

The researchers said prophylaxis is not always optimal "at least in part because tetanus can result from seemingly trivial wounds that would not trigger suspicion of tetanus risk," and because "clinical determination of tetanus-prone wounds is not exact."

Vaccination status was available for 92 patients, and just over 40% of them never received any dose of the vaccine. About a quarter received one dose, and another quarter received four doses or more.

The researchers said this suggests that physicians should review tetanus vaccination status during visits to make sure that tetanus booster status is up-to-date -- especially for older adults, injection drug users, diabetics, and those with chronic wounds.

Tiwari said children should receive a complete series of vaccine at ages 2, 4, 6, and 18 months, and then again between ages 4 and 6. An additional booster dose should be given between ages 11 and 12, and then every ten years after.

Overall, however, incidence of the disease remained low -- at 0.10 per 1 million population overall, and at 0.23 among those ages 65 and up.

The researchers noted it was higher among Hispanics -- nearly twice as high as the incidence among non-Hispanics -- but this was largely attributable to 16 cases among Hispanic injection drug users.

They said the study may be limited by underreporting in the database.

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