The measles outbreak in B.C.’s Fraser Valley has been declared over, health officials in the province said Monday.

The outbreak was the largest in decades, with more than 400 cases over a four-week period earlier this spring.

Dr. Paul Van Buynder, Fraser Health’s chief medical health officer, said there has been a vast reduction in the number of transmissions and new cases.

While occasional cases of measles may be seen, “the outbreak response in Fraser Health is now coming to a close,” Buynder said in a statement Monday. 

The outbreak began on March 8 after several children in a Christian elementary school in Chilliwack, B.C. contracted the virus. The community has traditionally low immunization rates.

The virus spread about a week later into the general population in the Fraser East region, including Abbotsford, Mission, Agassiz, Harrison Hot Springs and Hope.

Other cases were later reported near Vancouver, at the Burnaby campus of the British Columbia Institute of Technology, and in Whatcom County, Washington, after an American resident contracted the virus while in B.C.

Buynder said the size and speed at which the outbreak spread “resulted in more cases of measles than the province has seen in the past 15 years, and was the largest outbreak in almost 30 years.”

He added that National Immunization Awareness Week, which takes place from April 26 to May 3, is an important time to remind parents that vaccinations are “your best shot at protecting your children from these preventable illnesses.”