During the few past weeks, many people in California have fallen sick with the flu. But, so far, the season has proved milder than in recent years. Experts have come up with several reasons behind the lower impact of flu this season.

Health experts added that the existing vaccine is quite good for the flu strains and the virus is probably not spreading at a fast pace because of unusually warm weather. It is also possible that the outbreak hasn’t peaked so far.

Dr. Robert Schechter, medical officer with the immunization branch of the California Department of Public Health, said that it’s difficult to know where we are, if we are in the eye of the storm or the storm has gone.

Previous three flu seasons have peaked in December. However, February is usually the peak of the season, which can stay till May.

According to data released on Friday, since the starting of the flu season in October, 16 people in California, below 65, have lost their lives due to serious health issues. Last year, by this time of the season, death toll had reached 29, and 243 deaths two years back. Influenza B is another probable explanation for the low case numbers this season.

During each winter flu season, people get infected by viruses A and B, but B strains generally cause less severe illness.

As per the state data, so far in this season, 45% of Californians, who have suffered from the flu, had got infected with Influenza B, in comparison to 6% previous year and 7% the year earlier.

The Federal Centers for Disease Control and Prevention said that a similar trend has been noticed across the nation, with 32% of Americans diagnosed with flu in the present season have tested positive for Influenza B, in comparison to 6% and 9% in the last two years, respectively.