The H1N1 flu outbreak was a dominant health story of the year, and the city bore the worst of the virus's wrath in the spring. NY1's Health reporter Kafi Drexel filed the following report.

The H1N1/swine flu virus started off as a mystery illness, sickening hundreds and killing dozens in Mexico in early spring 2009. The unique H1N1 virus, never seen before this year, is made up of a combination of genes from pig, bird and human flu viruses and spreads easily from person-to-person contact, similar to regular seasonal influenza.

Before long, the virus was carried back to New York, by students from St. Francis Prep in Queens who were vacationing in Mexico. Before long, the school became the first major cluster of a global outbreak.

Health officials reassured that the new virus is no different from regular seasonal flu, but even seasonal flu can be a killer. H1N1 acts no differently, and sickens mostly children and young adults who also suffer some of the greatest complications. By comparison, it's usually the very young and very old who are most at risk from seasonal flu.

More cases were confirmed across the country and the city prompted hundreds of school closures. People with flu-like symptoms clogged emergency rooms.

Short of vaccine, usually the first line of defense with any flu, health officials reminded the public to wash hands, cover coughs and sneezes and stay home if they felt sick to help stop the spread of infection. Those with pre-existing medical conditions like diabetes, respiratory illness, pregnancy and heart disease are warned to be especially cautious.

By summer, flu activity dropped across the country, but then spiked once school children and college students return for fall classes. Academic institutions took preventive measures like having emergency flu plans in place and handing out hand sanitizer to keep germs at bay.

Less than six months after H1N1 first appeared, health officials announced a vaccine was ready. By early October, the first doses are distributed across the country and in New York City.

But the vaccine was in short supply, creating lots of confusion as to where to find it and getting it to those who needed it most first -- young children, pregnant women and those with already-compromised health.

By mid-December, more than 95 million doses of the vaccine were given out across the country, which was far fewer than the 120 million doses health officials were hoping would be ready before November.

Nearing year's end, there have been about 50 million cases of H1N1 -- about 1 in 6 people nationwide -- 200,000 hospitalizations and nearly 10,000 deaths, mostly among children and young adults. Such statistics are much higher stats than those from the regular flu season.

While there was a spike in reported deaths, flu activity is down across the country and never really peaked again in New York City the way it did in the spring. Yet that does not spot people from getting vaccinated, as they fearing a resurgence at any time.