It's common to see a second wave of flu in the late winter or early spring in the US, but that's not exactly what's happening now, government officials said.
"I think Wave is a bit strong – mainly because it makes people think we will see a rise or a high peak of cases, as we saw in January and February," said CDC spokeswoman Kristen Nordlund opposite NBC News.
Influenza activity continues to decline, but influenza B viruses are more In recent weeks, reports have been more frequent while the proportion of influenza A viruses has decreased, Nordlund added.
Influenza B infections can be as severe as those associated with influenza A, but influenza B is usually worse in younger children. It is not clear why this is the case.
This year's vaccine protected 42 percent of people from getting B influenza so much that they could go to the doctor.
People who are already suffering from influenza A are still susceptible to the B strain. That's because your body will develop antibodies against it when you kill a flu virus, but they're useless against various flu viruses.