Dr Lance Jennings of the National Influenza Specialist Group said this flu season was more severe than last year's.
"Most of the South Island and the Wanganui region are above average at the present time," he said.
"We're approaching the levels that we saw in 2011 and 2012, but it's not as bad as what we've seen in some other years."
The circulation of new strains of influenza was probably behind the increase in cases, he said.
The season was currently peaking and would likely come to an end at the end September, he said.
The Tairawhiti District Health Board had the highest number of reported GP consultations, with a total of five cases, or 486.4 per 100,000 registered patients.
This was followed by the South Canterbury District Health Board, with 24 cases, or 262.2 per 100,000 registered patients.
Meanwhile, the Waikato District Health Board had no reported consultation rates.
Tairawhiti District Health Board's medical officer of health, Margot McLean, said although recently released figures showed that Tairawhiti had the highest consultation rate for influenza-like illness, figures were based on small numbers.
"The apparently extremely high rates in Tairawhiti are based on very small numbers, so we can't rely on those rates as suggesting we are experiencing anything abnormal for this time of year," Dr McLean said.
"Flu rates are higher than the last two years, but similar to those seen in 2012. But rates may not have peaked yet."
Meanwhile, head of Tairawhiti's Emergency Department, Dr Johan Peters said they were seeing the normal number of patients for this time of year.
"The numbers coming through are not putting undue strain on our resources and are quite within our capacity to cope."
Dr McLean said influenza was a serious virus and could be life-threatening, especially for people who already had existing serious health conditions.
"People at risk of complications are advised to get vaccinated if they have not done so already. Vaccinations are available until the end of August."
Dr McLean said symptoms of influenza could come on suddenly and could include fever, chills, muscle aches, runny nose, cough and stomach upsets.
"People who are unwell with influenza should stay away from work and school, and seek medical advice if they are concerned, either by contacting Healthline or their medical centre.
"It is important that people with flu symptoms avoid visiting people in hospital or rest-homes, as they could spread the infection to people who are at risk of serious complications."
-- additional reporting Catherine Gaffaney
