Southern District Health Board medical officer of health Dr Marion Poore said there was usually an increase in such illnesses in spring, with most cases in farm workers or young children living on farms where they came in contact with newborn animals.
While the illnesses did not usually require treatment other than re-hydration, careful hygiene was needed to prevent spreading.
Two infectious diseases increasing in prevalence were cryptosproridium and Salmonella brandenburg.
Cryptosporidium was a parasitic infection most often seen in people who had close contact with animals or who were exposed to contaminated water. Increases were noted during the calving season.
So far this year, there had been 38 cases notified, 11 of them in the Dunedin City Council area, which possibly reflected the city's rural surroundings.
Last year, 51 cases were notified, eight higher than for the previous year.
Since the beginning of August, there had been 10 notifications of Salmonella brandenburg, compared with three in the corresponding period last year.
Some of these cases had been associated with outbreaks of the disease on sheep farms.
Last year, slightly more than half the 36 cases of this illness notified throughout the country came from Otago and Southland, with 75% of them occurring between September and November.
The best way to prevent either infection was with "good old-fashioned soap and water", Dr Poore said.
Hand sanitisers could be useful in situations where it was not possible to wash hands, but they were not effective where dirt was visible, or people could feel "pilling" of dirt on their skin.