For most people who contracted swine flu it was a mild illness, but for others, the virus resulted in hospitalisation and an ongoing battle for life.
Whether next winter will bring a second wave of the pandemic is unknown, but the Ministry of Health warns it is still important people maintain good hygiene habits.
As the first wave of swine flu (H1N1 A) subsides in the Southern Hemisphere, Bruce Munro looks at its impact on the region.
Swine flu victims have spent up to five weeks on ventilators in Dunedin Hospital's intensive care unit (ICU).
As the first wave of swine flu (H1N1 A) subsides in the Southern Hemisphere, doctors, including Dunedin Hospital ICU consultant Dr Matthew Bailey, are starting to get a better understanding of how the new virus affects people.
In a small group of otherwise healthy people, swine flu seems to cause the body to attack itself, necessitating the use of ventilators to keep the person breathing, Dr Bailey says.
"In my experience it is quite a nasty, virulent disease. But we are talking about how it affects a very small sub-group," he said.
Since swine flu reached the South in April, Dunedin Hospital has had at least five patients on ventilators who were most likely being treated as a result of contracting swine flu.
One patient died.
Another patient, Terri Gordon-Davis (39), has been on a ventilator for more than 37 days (read her story on page 2).
Because people received treatment as soon as they were admitted to hospital, it had been difficult to confirm whether all the suspected cases in ICU were indeed swine flu, Dr Bailey said.
"One absolutely, one likely, three we're quite suspicious it was swine flu, and there were maybe some others."
"The vast majority of people get better without requiring treatment, but for a small group it causes long-term lung injury."
While there was not yet a lot of data, the impact of swine flu "seems to be driven more by how a person responds to the disease than the disease itself".
For the most seriously affected group, the patients' inflammatory system attempted to destroy the invading organisms and irreparable tissue, but then, rather than the body switching to rebuilding and recovery, the destructive phase continued and "seems to get out of control".
"The swelling produces fluid in the lungs, which makes it hard for the oxygen to move into the blood," Dr Bailey said.
Most of the patients had been on ventilators for between four days and three weeks.
Mrs Gordon-Davis was still on a ventilator after five weeks in ICU.
"We haven't had enough cases to follow long term to know, but we hope and expect the severe patients will get fully better."
The other distinctive aspect of swine flu was that those severely affected tended to be young, healthy people, Dr Bailey said.
At least half were either pregnant or overweight, but would not normally have required hospital treatment.
