On day two, her sister was taken to a medical centre and diagnosed with pneumonia and prescribed antibiotics.
Deteriorating "rapidly", the sister was taken back to the medical centre on March 13, day eight, after her health had gone "downhill".
"It was like the lights were on but no one was home," Nikki said of her sibling.
"She was disorientated. She just said she felt miserable, I don't think she really knew what was going on."
Nikki grew confused and desperately concerned for the well-being of her sister, who fell into a semi-conscious state while being taken to hospital via ambulance.
At the hospital, she was soon placed in the intensive care unit as her breathing had become "very fast", a sign oxygen was not entering her lungs properly.
Last week, Nikki's sister was diagnosed with the H1N1 virus, also known as "swine flu".
"I was absolutely stunned with the diagnosis, [H1N1] had never crossed my mind," Nikki said. "I never thought it could be anything as serious as this. We hadn't thought about vaccination yet because it was still summer."
Now day 20, and with her sister having spent 12 days in hospital, sedated and ventilated, Nikki is gravely concerned.
"The rapidity of moving from what we initially thought was pneumonia to being desperately ill, it's shocking and scary."
Infectious-diseases physician Andrew Burns said the flu season has struck Hawke's Bay early.
"June or July is usually when we see more cases but we have been aware of cases coming into the hospital since January - some of them have been quite sick." North America had experienced a "particularly nasty" flu season and 90 per cent had been H1N1, for which 40 per cent of the US population was vaccinated. Dr Burns said in New Zealand the number was about 25 per cent.
More people needed to be aware the virus was circulating. The elderly, people with chronic health conditions or pregnant "should certainly be proactively seeking out vaccinations".
H1N1 had been included in the vaccine since 2009 and in 2010 the Ministry of Health released figures from a scientific study showing the full effect of Pandemic Influenza H1N1 in 2009. The highest rate of infection was in school-age children, with one in three affected. Almost half of those infected showed no obvious symptoms.
"We very much advocate even healthy adults should consider receiving the vaccine," Dr Burns said. "The Centers for Disease Control in America - the largest public health service - has for the last two years advocated everyone over 6 months of age should receive the vaccine."
Those under 6 months often did not respond to the vaccination and he said the best way to protect a baby was to limit contact with potentially infected people.
There was concern the high North American infection rates might be repeated in New Zealand but it was always "difficult to project".
The disease was usually contracted through tiny droplets of spittle emitted when people talked, he said. The droplets then made their way into people's mouths.
Hawke's Bay District Health Board medical officer Caroline McElnay said flu strands killed about 400 New Zealanders, directly or indirectly, each year and hospitalised more than 1000 last year.
Dr McElnay said: "While it's important that vulnerable people are protected, even healthy people can get the flu and die from it."
The Hawke's Bay District Health Board is starting its Come on the Bay Get Immunised campaign to help fight any potential epidemics this year.
