Canadian and U.S. health authorities are seeing more flu cases than usual for this time of the year, which could signal a fast and furious start to the influenza season.
Influenza activity usually peaks in January or later. But the pandemic H1N1 virus strain kept its footing in the northern hemisphere through the summer - and one study is now predicting that it could peak in October, well before most people are vaccinated.
The Canadian government indicated Thursday that flu activity this week slightly decreased, but cases are still higher than expected. The U.S. Centers for Disease Control and Prevention found that six states, including Alabama, Florida and South Carolina, reported widespread flu activity in the last week of August.
"Any widespread influenza activity in August is uncommon," the CDC said in its Morbidity and Mortality weekly report.
"Clinicians and public health officials should be aware that these recent increases might signal an early start to the 2009-10 influenza season, with pandemic H1N1 influenza viruses predominating at least initially."
Canada has ordered 50 million doses of vaccine for all those who want and need it. David Butler-Jones, the country's chief public health officer, has indicated that the vaccine could be ready as early as October if the swine-flu virus quickly turns more severe.
"I think the next week or two, now that kids are back in school, we'll have a clearer sense of whether this is going to be continued sporadic cases and small outbreaks, or whether this will be the harbinger of the next wave," he told reporters in a conference call Thursday.
A study published in Science Express, the online edition of the journal Science, found the current pattern of pandemic spread is similar to the Asian influenza pandemic of 1957-58, where substantial spread was expected to begin in early September with the epidemic peaking in mid-to late-October.
"In this case, child-first, phased vaccination would need to start as soon as possible, and no later than mid-September to be effective for mitigation," said Ira Longini, one of the authors of the study and a professor of biostatistics at the University of Washington School of Public Health.
Dr. Butler-Jones said if the pandemic hits hard in the next month, there's no reason to panic because influenza doesn't come in only one wave.
"Even if we see lots of disease in September and we're not able to immunize till later in the fall, it's still going to be important to do so," he said.
Further, Canadian health officials are hopeful that the guidelines in place, including infection prevention strategies, will slow the spread of the virus.
"It's not just a vaccine strategy. It's not just an anti-viral strategy. It's not just about education. It is in fact a package. That all these measures can do several things, one of which is to slow down the spread and to smooth out that curve so that we will hopefully see a later peak and have far more people immunized in advance of that," Dr. Butler-Jones said.