Health officials in Erie County, New York, said Saturday that a rare, travel-related case of diphtheria may have exposed people at schools in the West Seneca Central School District, The Buffalo News and WIVB reported.

Notices went to families at four schools: Clinton Primary, Northwood Elementary, Winchester-Potters Elementary and East Middle School, WIVB reported. "Based on an abundance of caution, we are working with district leadership to inform students, staff and families," the county health department said, according to The Buffalo News.

Families should watch for symptoms through Oct. 18. Signs include a sore throat, fever, swollen glands in the neck, a thick gray coating in the throat and skin sores. Anyone who gets sick should call a doctor, mention the possible exposure and stay home until cleared. In a letter to Northwood families on Friday, the principal said the risk of infection is "extremely small."

The county is checking student vaccine records with school nurses. It may send more notices to students who are not fully vaccinated. A county spokesperson said the case is in an Erie County resident. She had no details Saturday on which form of the illness it is, The Buffalo News reported.

Diphtheria is a serious infection caused by bacteria. It spreads through droplets from coughs and sneezes or by touching infected skin sores. One form attacks the throat and can make it hard to breathe. The other affects the skin. "The good thing to know is that this is a vaccine-preventable disease," Dr. Karl Yu of the University at Buffalo told WIVB. The danger is "fairly minimal for anyone who is routinely vaccinated," he said.

A century ago, diphtheria was a common cause of death among American children. Routine shots for children began in the 1940s. Today, kids get five doses of the DTaP vaccine by age 6 and a booster around age 11 or 12. Adults are told to get a booster every 10 years. The county says just 10 cases have been reported in the U.S. in the past 20 years. The last confirmed U.S. case of the throat form was in 1997, The Buffalo News reported, citing the CDC.

What we know: One travel-related case was confirmed in an Erie County resident, and families at four West Seneca schools were told to watch for symptoms through Oct. 18.
What we don't: Which form of diphtheria the patient has, or whether anyone else has been infected.