As kids head back to school after the holidays Monday, health officials in B.C. are warning of a nasty flu bug sweeping the province.

While many families have already been hit over the holidays, officials say this flu frenzy, which causes fatigue, aches and a nagging cough, is the worst strain they've seen in years.

Health officials say half of all the respiratory illness samples being tested at the BC Centre for Disease Control are now testing positive for the H3N2 influenza virus.

Fraser Health's chief medical health officer Dr. Paul Buynder said this strain causes much more intense, extreme symptoms, and the season is just beginning.

"The flu season has just begun and it appears to be getting worse. We're expecting this will continue right through the winter to March," Buynder said. "We've seen a number of outbreaks... lots of deaths, particularly in long-term care units, and a number of children in the U.S. have passed away just from influenza this year."

Doctors say it’s a particularly severe flu bug that can be most harmful to the elderly and those with chronic health conditions.

With children heading back to school Monday from the holiday break, officials say thousands will be exposed to the virus.

But there are ways to protect yourself, such as getting plenty of sleep, washing hands often, eating healthy and taking vitamins, according to health officials.  

Buynder said the most important thing is to get vaccinated.

Flu shots are still available at many pharmacies, however they can take up to two weeks to build enough antibodies to fight the bug.

"Apart from that, stay home if you're sick, don't soldier on and spread it," Buynder said.

Antivirals, such as Tamiflu, are recommended for people who are at a high risk of complications and for those who are already sick.