The gastro outbreak in Havelock North is estimated to have cost the Hawke's Bay District Health Board $380,000.
More than half of that figure, $216,000, was due to staff sickness, chief executive Kevin Snee said.
The next biggest item was additional costs in treating patients in intensive care, which was put at $66,000.
More than 5000 people were hit by gastric illness in August because of contamination of Havelock North's water supply.
The Government is conducting an independent inquiry into what happened and the inquiry panel is expected to report their findings by the end of March.