It's flu shot time, and health officials are bracing for a potentially miserable fall and winter.
The Southern Hemisphere, especially Australia, was hit hard over the past few months with a flu strain that's notorious for causing severe illness, especially in seniors.
And in the U.S., small clusters of that H3N2 flu already are popping up.
"We don't know what's going to happen but there's a chance we could have a season similar to Australia," Dr. Daniel Jernigan, influenza chief at the U.S. Centers for Disease Control and Prevention, told The Associated Press.
The worrisome news came as the government urged Americans Thursday to make sure they get a flu shot before influenza starts spreading widely. Health and Human Services Secretary Tom Price got his own jab to publicize the importance, saying, "There's no reason not to get protected."
The CDC's Jernigan cautioned there's no good way to predict how bad the upcoming flu season will be. An H3N2 strain caused infections in Canada and the U.S. last year, too.
Sometimes watching what happens in the Southern Hemisphere is a good predictor of what to expect in the Northern Hemisphere and sometimes it isn't, said Dr. Michelle Murti, a public health physician at Public Health Ontario who conducts influenza surveillance.
"I think it's an important signal and something we need to be aware of," Murti said in an interview Friday.
"The message that I think we would want to be taking from that is a reminder that flu season is quite severe."
H3N2 is "the bad actor," said Dr. William Schaffner of Vanderbilt University and the National Foundation for Infectious Diseases. "If you needed another reason to get vaccinated, there it is. Best get that protection."
Murti said that typically H3N2 can be more severe than other strains among those over age 65 who are at higher risk of complications. In Canada, there tend to be more outbreaks in long-term care facilities when H3N2 is the predominant strain.
World Health Organization flu advisers meeting in Australia recommended updating future vaccines for the Southern Hemisphere to strengthen H3N2 protection.
Flu does constantly evolve, forcing new vaccines to be brewed each year to match the strains specialists expect to cause most illness. In the U.S., CDC's Jernigan said this year's shots aren't perfect — but that the H3N2 strain travelling around the globe hasn't significantly changed, so the vaccine remains a pretty good match.
"It's the best tool we have right now for preventing disease," he said in an interview.
The Public Health Agency of Canada's first Fluwatch report of the 2017-18 season says flu activity remains at inter-seasonal levels across the country, with a few regions reporting sporadic or localized activity. The majority of influenza A virus subtypes were A(H3N2).
"The 2017-18 flu vaccines available in Canada this year contain the same components as those recommended by the World Health Organization for the Northern Hemisphere," a spokesperson for the Public Health Agency of Canada said in an email.
Across Canada, Murti said flu vaccines are now being shipped to distributors. Most provinces and territories start their annual flu vaccine campaigns toward the end of October.
Murti recommended those at high risk of influenza complications get vaccinated. This includes:
Those who live or work with any of the above should also be vaccinated.
The effectiveness of influenza vaccines varies from year to year, ranging from 40 per cent to 60 per cent, Murti said
To prevent flu, public health officials also recommend:
The start of Canada's flu season tends to peak anywhere between November and January, Murti said.With files from CBC's Amina Zafar