180 cases of cryptosporidiosis have now been confirmed in Galway city and county.
The rate of reported infections has slackened to one per day.
The Health Service Executive has not yet published the latest results of tests to identify the source of the cryptosporidium parasite.
Test results early last week showed that in 19 of 24 confirmed cases of cryptosporidiosis, the parasite came from human sources.
Meanwhile, Galway City Council will tonight unveil a scheme that will provide local householders with bottled water at reduced prices.
Some 90,000 people in Galway city and parts of the county have had to boil and buy water in recent weeks, because of the contaminated supply.
The council has also requested that the Department of Social and Family Affairs begins a water voucher scheme to cater for social welfare recipients.
The city's Mayor, Niall Ó Brolcháin, said the move would be temporary until a clean water supply is restored in a few weeks' time.