Rural communities are experiencing a seasonal increase in cryptosporidiosis, a parasitic infection which causes abdominal pain and severe diarrhoea.
It's most commonly seen during spring, in people who have close contact with animals or are exposed to contaminated water.
Otago medical officer of health John Holmes says there have been 22 cases there compared with 14 the same time last year.
He says thorough handwashing after handling animals is the best way to avoid contracting the illness.
Dr Holmes says the spike in the number of cryptosporidium cases is likely to continue for at least another month.