Up to 79% of New Zealanders could ultimately catch H1N1 influenza during the epidemic, although not all will become ill, a new study from Wellington-based University of Otago researchers shows.
It is an estimated reproduction rate that is higher than that of the Spanish influenza pandemic of 1918-19, but the mortality rate is very low compared with that disaster in which thousands died, a letter in the New Zealand Medical Journal says.
The latest estimate of the virus' spread, by Associate Prof Michael Baker and Dr Nick Wilson, of the university's public health department, and Dr Hiroshi Nishiura, from the University of Utrecht in Holland, was detailed in the journal.
They give an estimate for New Zealand which suggests that a person who was ill with the new strain would on average infect almost two others.
Prof Baker said that estimate would require a high level of mixing between groups and effective public health interventions could lower that proportion.
New Zealand had a higher reproduction number than Mexico, possibly because of the winter season and large clusters of cases in certain settings, the researchers said. However, further work would be needed to produce more robust estimates for New Zealand.
The Ministry of Health's principal medical adviser, Dr David Galler, said health services would remain under pressure for some time yet, as the pandemic virus continued to spread, but the system was coping well.
The vast majority of New Zealanders who had swine flu experienced mild to moderate symptoms. "Most of them recovered without requiring medical attention within a week from the onset of symptoms."
Otago and Southland district health boards' incident controller Leanne Samuel said hospitals in the districts did not have any people with swine flu in intensive care and none had been transferred from Christchurch.
In Dunedin, doctors were coping with increased numbers of patients with flu symptoms and schools had not reported any increase in absenteeism, she said.
University of Otago pandemic response group spokesman and student services director David Richardson said Student Health was managing higher levels of students who were unwell, as was normal during the winter. The presence of H1N1 had added to this but remained well within manageable levels.
"Most students seem to be taking sensible precautions."
