Four elderly residents have died and a nursing home is in lockdown amid a flu outbreak in New South Wales. 

The Marco Polo Aged Care Services at Unanderra, south of Wollongong, has been quarantined since June 10, with five residents taken to hospital, twenty staff diagnosed with the flu and 15 isolated at the centre.

Manager Robert O'Shae says the facility is managing the outbreak in consultation with the NSW public health unit and families have been asked not to visit the centre as it tries to control the situation.