Bloomfield said he didn't have a timeframe for when New Zealand will experience community spread.
"We are watching very closely as to whether we have any community spread. We also want to act before we see any evidence of widespread community outbreak.
"We've seen a big increase in the number of tests being done, only a few of those cases are testing positive, but it does give us a good idea of whether there's wider community transmission. We're testing people with wider influenza symptoms and it's not at this point been Covid-19.
"There's a lot of work going on to confirm our labs have everything they need to conduct the tests, get the results out quickly, identify the positive results and contact trace."
Bloomfield said some of the earlier cases will have now recovered but they all needed to stay self-isolated for 14 days once they have recovered.
Some elective surgery is being postponed so staff can be upskilled on how to care for people who are ventilated.
"This is not a time for panic," Ardern said yesterday. "It is a time for preparation."
Ardern urged anyone who had arrived back in the country in the past fortnight to go into self-isolation, even if they arrived before the requirement for self-isolation.
Bloomfield told Newstalk ZB earlier today that there's been a big increase in testing over the past two to three days.
Bloomfield said 500 or 600 tests are now being done each day.
He said the positive tests have only been from those who've returned from overseas.
The increase in cases parallels a ramping up of testing from about 600 in the past six weeks.