Health officials are warning there has been an outbreak of whooping cough in the Hope area of the Fraser Valley, east of Vancouver.

There have been 20 cases reported since August, including 15 since December, according to a statement issued by the Fraser Health Authority on Wednesday morning.

The health authority is asking healthcare professionals and members of the public in the Hope area to be alert for the signs and symptoms of Pertussis, or whooping cough.

"It has been many years since British Columbia has had an outbreak of Pertussis so there is very little natural immunity," said Dr. Paul Van Buynder, the Fraser Health Authority's chief medical health officer, in the statement.

Buynder is advising residents to ensure all the vaccines of all family members are up to date.

"The best protection against Pertussis is to get vaccinated. Pertussis in very young children can lead to hospitalization and even death," he said.

"The vaccine that most people get when they are infants only offers protection for four to 10 years, so there are many people without adequate coverage."

The preliminary results of a recent U.S. study suggested the vaccine against whooping cough falters after only about three years.

Free booster shots for adults

The Fraser Health Authority is offering a free booster vaccine to adult residents of Hope who are in regular contact with young children. Adults in that category who have not had a booster in the last five years are asked to contact the Hope Public Health Unit at 604-860-7630, their doctor or health care provider to receive the free vaccine.

"Whooping cough, which is also called Pertussis, causes very severe coughing that may last for months. It is very contagious and can be a severe illness in those without adequate immunizations," said the statement.

"Whooping cough spreads easily through the air when an infected person coughs, sneezes, or laughs, putting bacteria into the air. After the bacteria infect someone, symptoms appear about seven to 14 days later."

Officials say early symptoms include sneezing, runny nose, a low fever and a mild cough, but gradually progress to "longer spells of coughing that often end with a whoop or crowing sound when the person breathes in."

An outbreak of whooping cough was detected in the West Kootenay region in Feb. 2010. The cases were largely amongst children who were not immunized.