In its weekly flu report, issued Friday, CDC officials said they saw a decline in overall influenza cases for the week ending March 17. The decline was particularly apparent for the A-strain of the virus, which has been dominant since the flu season started in October.
However, officials noted that they’ve seen more reports of the flu virus’s B-strain, which has been slowly overtaking reports of influenza A. For the week ending March 17, influenza B made up about 58 percent of the week’s total flu reports.
The virus strain, while different, can pose just as many health problems as the A-strain, according to the CDC.
"We know that illness associated with influenza B can be just as severe as illness associated with influenza A," CDC spokeswoman Kristen Nordlund told CNN. "We also know that influenza B tends to be more severe for younger children."
Officials said five children were confirmed to have died of influenza during the week ending March 11. Two of the deaths were associated with the influenza B virus. Overall this flu season, 133 flu-related pediatric deaths have been reported.
Officials recommend that unvaccinated people get the flu vaccine, as influenza viruses continue to circulate. Last month, officials said the vaccine “usually (works) better” against influenza B and H1N1 viruses than it does against the H3N2 virus most common this flu season.
Norlund told CNN that the second wave of influenza cases was not unexpected.
"We often see a wave of influenza B during seasons when influenza A H3N2 was the predominant virus earlier in the season,” she told the news network. “Unfortunately, we don't know what the influenza B wave will look like."