A whooping cough outbreak in the Fraser Valley appears to be spreading into Metro Vancouver with 38 confirmed cases detected across the region in January, health officials say.

Vancouver Coastal Health that's more than three times the usual number of cases for this time period, and as a result it is now offering free vaccines to pregnant women, their partners and for anyone with children under 18 months.

"Since the outbreak in the Fraser Valley began in December, we’ve been closely monitoring the incidence of whooping cough in our region." said Dr. Patricia Daly, the chief medical health officer for Vancouver Coastal Health.

"Because the number of cases has risen over the last week in the Vancouver Coastal Health region, we are stepping up measures to protect residents."

The health authority says whooping cough causes coughing fits that can turn into severe illness and may last for months. It spreads easily through the air when an infected person coughs, sneezes, or laughs. It can be a very serious illness, even fatal, in young infants.

The free vaccine is available through family doctors’ offices, public health clinics and some pharmacies. Details are avaliable by calling HealthLink BC at 8-1-1.

The Fraser Health Authority began offering the vaccine free last month, after seeing 140 cases in the region.