Increasing Though Still Rare, Meningitis Cases in U.S. Are Traced to Nasty Bacteria : Health: Outbreaks of group C meningococcal diesase are being closely watched.

A bacterial infection that can cause fatal meningitis or blood poisoning is striking with increasing frequency in the United States, federal researchers report.

Outbreaks of group C meningococcal disease are still too rare to cause alarm but are among emerging threats that health experts are watching. Group C is one of three main types of meningococcal bacteria, a type of germs that live harmlessly in the noses and throats of up to 10% of healthy American adults and up to 20% of college students.

Meningococcal germs sicken people when the organisms invade the body, usually the nervous system, causing meningitis.

They can also invade the bloodstream, causing a type of blood poisoning.

About 2,600 Americans annually--mostly children under 2--suffer either from meningitis or the related blood poisoning.

Only occasionally are there outbreaks of the disease in clusters.

But since 1991, group C outbreaks have been increasing, for unclear reasons, the researchers reported in a recent issue of the Journal of the American Medical Assn.

A similar increase is occurring in Canada, researchers from that country reported in an accompanying article.

“Meningococcal outbreaks are one of the most feared public health emergencies,” said the U.S. researchers, led by Dr. Lisa A. Jackson of the federal Centers for Disease Control and Prevention. She has since joined the School of Public Health at the University of Washington in Seattle.

The disease strikes seemingly at random, sickening people who were previously healthy and killing one in seven, often within hours. A vaccine exists, but it is expensive, ineffective in children under 2 and provides only temporary immunity.

Mass inoculations are ordered when the disease can be identified while it is spreading through older populations, they said.

Such mass inoculations have been offered twice in Illinois in the past four years.

In 1992, an outbreak at the University of Illinois in Champaign-Urbana sickened nine people, killing three of them. In February, 1994, about 22,000 children in Springfield were vaccinated after 10 youngsters fell ill and two died from group C meningococcal disease over a one-year period.

To explore the nationwide pattern of group C meningococcal outbreaks from 1980 through mid-1993, the researchers searched CDC records, scoured medical literature, queried state health departments and solicited information from the only U.S. manufacturer of vaccine for group C meningococcal disease.

They found a total of 21 U.S. outbreaks involving three to 45 people each.

Only six outbreaks occurred in the first eight years of the period, while 10 occurred in the last 2 1/2 years, a “relatively dramatic increase,” the researchers said.

They speculated that a new family of genetically related group C bacteria may be responsible, but no one can be sure.

“We think it represents change in [disease] patterns we need to be aware of,” Jackson said.

“But as far as a threat to the average person, it’s really not a very big concern.”

Dr. Barry Fox, head of infectious diseases at Carle Clinic in Urbana, Ill., one of the main doctors who treated the 1991-92 campus epidemic, agreed.

“In terms of this having a potential tangible impact on the general public, the significance would be very small,” he said.