The Ministry of Health's computer system has been hit by virus.
The ministry says its internal computer system contracted the mutating virus on 30 December, affecting internal mail services and forcing it to take its websites offline.
Deputy director-general of information Alan Hesketh says the virus slowed the performance of the computer network and has been particularly hard to get rid of.
He says the virus has had no impact on health services.
Mr Hesketh hopes the last of the virus will be destroyed on Wednesday, after which the ministry will review its computer security systems.