There’s far less sneezing, wheezing and coughing in the air this year — flu season is largely missing in action across North America.

The U.S. Centers for Disease Control and Prevention has reported the lowest influenza infection rate in 30 years of tracking flu activity, as well as the slowest recorded start to the flu season.

FluWatch in Canada and Google Flu Trends confirm those trends, said Dr. Peter Lin, a Toronto family doctor and commentator on CBC’s Metro Morning radio show.

"Normally, the flu season would have peaked by now," Lin said. "Right after Christmas and New Year’s we usually see a bump in flu numbers because people have gathered for the holidays, but that hasn’t happened at all this year."

Dr. Peter Lin says a mild winter has contributed to a drop in flu activity this year. (Peter Lin)

For example, he said, compared with the flu pandemic of 2009-2010 when 40 regions across Canada were reporting flu outbreaks, this year there are five a week, typically in schools and nursing homes.

"In 2009 when they graphed it, it looked like the Rocky Mountains and this year it’s just small nubs," Lin said.

The infection rate on swabs of people exhibiting flu-like symptoms is also down to just 10 per cent this year from a high of 40 per cent in 2009. That means most people who think they have the flu just have a cold.

Five reasons why there is less flu this year:

A mild winter

"The influenza virus likes the cold, dry air because that dries out our lung lining so it can get into cells easier. The virus needs our machinery to make copies of itself inside our bodies," Lin said. The unseasonably warm weather also means people are spending less time indoors exchanging germs, so there is less chance of spreading the virus.

More sun equals more vitamin D

Also known as the sunshine vitamin, vitamin D is believed to play a role in boosting the immune system. With more sun this winter and people spending more time outdoors, our bodies may be better able to fight off the flu.

"In tropical areas, flu activity is highest during the rainy season when there is less sun and less vitamin D," Lin said.

Lots of people got their flu shots

More than 36 per cent of Americans have been vaccinated against the flu this season, while in Canada it’s more than 40 per cent. "It’s the concept of herd immunity," Lin said. "If you have enough people vaccinated, the virus has a lot harder time gaining a foothold."

Flu viruses are unchanged

The main flu viruses circulating this year have been around for a couple of years, so many people, particularly those who have been vaccinated, were already exposed to them and built up a natural immunity, Lin said.

Flu awareness campaigns are working

People got the messages about frequent hand-washing, doing fist bumps instead of shaking hands, staying home when they’re sick, and sneezing into their arms, which all help to reduce the transmission of flu.

"Because everybody did their little bit, that’s how we got rid of the pandemic and if we keep doing those simple things we can help prevent another pandemic," Lin said.

The most important thing people can do to avoid spreading the virus is not touching their face with their unwashed hands, Lin said: "The virus gets on your hands and when you bring it up to your face, you breathe it in and gets into your lungs where it incubates."

Flu season not yet over

However, while numbers are down overall, cases are starting to pick up in two American states —California and Colorado.

"We have started to notice a few more cases in just the last week, so we’re not necessarily out of danger yet," said Lin, who came down with flu himself recently.

It’s hard to predict what will happen next year, and Lin warns against complacency.

Scientists have recently discovered the flu virus in bats, which means it could mutate into a new strain. If people forgo the flu shot this fall and become lax about other precautionary measures based on this year's lackluster flu season, our herd immunity will be lost, Lin said.