And, the seasonal flu can "shift and mutate" each year, which is why there are various flu vaccines available.
As of December 29, New Brunswick had 579 lab-confirmed cases, 577 of them influenza A and two of influenza B. Of those, 71 people were hospitalized, 15 were admitted to the ICU and there were three deaths.
During the last week of 2018 in Missouri, 653 cases of influenza were confirmed through laboratory testing.
Children less than two years old and adults older than 65.
Dr. Walshak says it's not too late to get the flu shot.
Data shows that the number of flu cases are likely to spike in the coming weeks.
Flu season lasts until May.
Moore said physicians at CHEO are seeing cases of RSV (respiratory syncytial virus) and other viruses as well as some flu.
By the end of October 2018, 185 pediatric deaths from flu complications were reported to the CDC, with 80 percent of deaths occurring in children who hadn't been vaccinated against influenza.
Peak flu season is starting now, and doctors say to get ready for a potentially extended season.
"We want to make sure that we get a handle on this before it gets worse".
While H1N1-predominant seasons tend to be milder overall at the population level compared to those characterized primarily by H3N2, individuals who get hit with either strain won't detect much of a difference - both bring on fever, cough, general malaise and achy muscles and joints, she said from Vancouver.
The hospital has not set a date when they anticipate to lift the restriction, but said that they will continue monitoring news about the flu season and then assess whether it will be safe to welcome children visitors back. At the time, the Advisory Committee on Immunization Practices for the CDC recommended the nasal for eligible children ages 2-8.
"While most people will get better themselves from flu, anyone who is concerned about their condition should telephone their GP or an out of hours medical service so they can arrange to be treated in a way that does not put others at risk", he explained.
The policy also urges visitors to wash or sanitize hands frequently while at the hospital to prevent getting the flu or potentially spread any illness.
It also highlights the need for influenza vaccine effectiveness estimates and the importance of the U.S. Influenza Vaccine Effectiveness Network in providing updated information for committee recommendations, he said.