There have now been 55 reported cases of a "nasty" strain of stomach bug hitting Hawke's Bay.
The cause of the Cryptosporidium, or Crypto, outbreak is not yet known, but health officials say it appears to be from more than once source.
A public notification on Monday alerted to 45 cases but yesterday that has risen to 55.
Hawke's Bay District Health Board Medical Officer of Health Nicholas Jones said the outbreak was potentially spreading through day care centres, drinking untreated water, and swimming in pools, lakes and rivers.
Crypto is contracted from a parasite found in the gut of cattle and other animals and is passed to humans through contact with animals, contaminated water or food, or direct contact with human waste.