Police authorities are trying to contain an outbreak of whooping cough at the New Zealand Police College in Porirua.

College spokeswoman Toni Barlow said four people had been diagnosed with whooping cough, with 34 more recruits put into isolation and taking antibiotics as a precaution.

The 34 were among 200 new recruits who began training at the beginning of the year.

One of the four had now recovered. Ten staff complaining of symptoms had also been sent home as a precaution.

Whooping cough may be fatal in children and the elderly, but is not normally dangerous to healthy adults.

Children are vaccinated against the illness, but the vaccination may wear off during adulthood.

Ms Barlow said communal diseases were to be expected in an institution where up to 600 people could be present daily, and 400 may be in residence.

"We're taking precautions. Anyone with a sniffle is being treated with antibiotics right now. Whooping cough in adults is relatively mild and more difficult to diagnose," she told NZPA.

Symptoms include a persistent dry cough that can be worse at night. The illness may last several weeks.

The affected police recruits were still able to study and training courses were continuing as normal, Ms Barlow said.