Plunket is asking parents to protect their babies from anyone with a cough after the Ministry of Health declared a national outbreak of the highly contagious illness whooping cough.

More than 1300 people have contracted it so far this year.

While infants are most vulnerable, the majority of cases in 2017 have affected older children and adults.

Plunket says whooping cough can have serious complications, and is often spread by family members or friends.

National clinical advisor Karen Magrath said the community has a role to play in fighting this outbreak, and people should make sure they're well before visiting a baby.