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Health scientists are closely monitoring flu cases, as they wait for the annual seasonal peak of illnesses to arrive.
Being the middle of winter, July is traditionally when flu infections reach their highest.
However, this year is different, the number of flu cases being reported are at very low levels.
Public health organisations staged extensive promotions to publicise the flu vaccine this year, in the wake of a flu season in the northern hemisphere where there were moderate to high levels of the disease and an increase in hospitalisations and deaths.
The number of flu cases so far in New Zealand was "unseasonably low", the ESR’s latest flu monitoring report said.
Only Auckland and Waitemata had high levels of flu — all others, including Southern, were continuing to report low rates.
However, those rates had shown a small increase, and ESR strategic health intelligence manager Lisa Oakley said infection rates could change quickly.
"Although the numbers that we are seeing are still low compared to previous years, our surveillance is telling us that they may start to rise soon," Dr Oakley said.
Following expected trends, children under 5 years old had the highest rate of flu-like symptoms but, again, much lower than last year, the ESR said.
New Zealand is not alone in having low flu rates — most southern hemisphere countries, barring South Africa, have reported lower than normal numbers of cases of the disease.
The low rates should not deter people from getting a flu injection, which was the best protection against catching the disease, Dr Oakley said.