The Fraser Health Authority has stockpiled 50,000 doses of whooping cough vaccine in case the growing eastern Fraser Valley outbreak spreads to other communities.

The whooping cough outbreak began in Hope in December, and spread to Chilliwack and Agassiz. So far, just over 100 cases have been reported, and one child has been sent to the hospital, said Fraser Health Authority spokesman Roy Thorpe-Dorward.

A few cases have also been diagnosed in Maple Ridge, Langley and Surrey. No one has died.

The 50,000 doses of vaccine will be readily available in case the alert needs to be expanded, Thorpe-Dorward said.

"We're hopeful that the effort we've made in Fraser Valley east will contain to those communities," he said. "Thus far, we haven't seen any significant cases developing outside those areas, but we'll continue to monitor the situation along with the provincial health officer."

Whooping cough -- named after the "whooping" sound that people with the sickness make when they are gasping for air after a coughing fit -- or pertussis, is a bacterial infection of the breathing tubes, and can be spread by coughing or sneezing. Coughs can last up to two months, and are usually treated with antibiotics. While the illness can seem like a nuisance to adults, it can be deadly for children under the age of one.

Thorpe-Dorward said cases of whooping cough occur across the province every year, but the health authority hasn't seen this number of cases in some time. Most adults receive vaccination as children, but the immunization wears off after four to ten years.

"Adults don't have any natural immunity," said Thorpe-Dorward. "If they were vaccinated as a child, they probably no longer have immunity, so cases of whooping cough creep in here and there."

Vaccination clinics have been running in Hope, Agassiz and Chilliwack for the past few weeks, and will continue into next week. Adults who have not had a booster vaccine in the last five years are encouraged to visit a clinic and get the free shot, and to make sure their children are fully protected.