So far this year, there have been 104 confirmed viral gastroenteritis outbreaks in the state's early childhood education and care sector.
The five-year average for the same period is 63 outbreaks.
Victorian Chief Health Officer Brett Sutton said children needed to be taught and reminded of the importance of handwashing.
"Gastroenteritis can spread quickly," Professor Sutton said.
"With the COVID-19 pandemic, disinfecting hands with alcohol-based hand rubs has become routine, but these are less effective for gastro bugs.
"Handwashing with soap and water is still the best personal hygiene method to minimise the chance of spreading the virus."
Another upsurge of viral gastro late last year saw 56 outbreaks in the six weeks to mid-December.
At the start of 2021, 389 cases were detected in childcare settings up to the end of April – four times higher than the average for that time of year.
Gastro symptoms include nausea, vomiting, diarrhoea, fever, abdominal pain, headache, and muscle aches.
They can take up to three days to develop and usually last between one or two days. In rare cases, it can develop into a more serious illness.
Infants or children in early childhood services or schools, as well as staff who develop vomiting or diarrhoea, should stay at home for at least 48 hours after their symptoms have stopped.
If symptoms are severe or they persist, people should see a GP for advice and testing.
Anyone recovering from gastroenteritis should avoid visiting hospitals, early childhood services, and aged care facilities to avoid spreading the infection to those most vulnerable.
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