Flu activity has surged nationally and in Massachusetts, reaching the highest levels recorded in recent years.

The Centers for Disease Control and Prevention announced on Friday that the country has not experienced this level of flu-like illness since the swine flu pandemic of 2009. Only four times since the agency began collecting data in 1997 has the United States endured a higher level of flu.

“It’s a very bad year,” Dr. Al DeMaria, medical director of the Massachusetts’ Bureau of Infectious Disease and Laboratory Sciences, said of the flu activity in this state. “It’s bad in two respects: It started much earlier than usual, and, after the holidays, we’ve seen a resurgence.”


Since 2007, the earliest year of available state data, Massachusetts has seen higher rates of flu-like activity during only three other stretches, in late 2012, during the 2009 swine flu pandemic, and in early 2008.

The statewide surge for the week ending Jan. 20 marked a significant spike from the previous two weeks, in which such reports declined, according to data released by the state Department of Public Health on Friday. Hospitalizations associated with the virus also increased.

“It’s an indication that flu season is not over yet — and that there is still plenty of reason to get a flu shot if you haven’t done so already,” state health officials said.

Massachusetts Department of Public Health

DeMaria said the season ramped up quickly, just in time for the December holidays. When rates subsequently dropped for two straight weeks, he and others thought the season may have peaked. But the most recent data suggest a strong resurgence.

“It might be related to people coming back together after the holidays and being in more situations where the virus can spread,” like going back to work and school, DeMaria said.


The latest announcement marked the first time this season that the state has declared flu activity in Massachusetts to be “high,” one of 39 states nationally with that designation. In previous weeks, officials had described flu activity in Massachusetts as “moderate.”

Flu activity has also been classified as geographically “widespread,” both in this state and nationally, meaning the virus has infected people in many different regions.

Massachusetts Department of Public Health

As bad as the problem may be in Massachusetts, it appears worse on the national level.

Since the federal government started collecting data 21 years ago, the United States has seen higher rates of flu-like activity just a handful of times: twice in 1999, in late 2003, and finally in the swine flu pandemic of 2009.

The deaths of seven children nationwide were associated with the flu in the week ending Jan. 20, according to reports submitted to the CDC. That brought the total number of flu-associated pediatric deaths in the United States this flu season to 37.

That figure is believed to understate the true total because of lag time in reporting deaths. CDC officials said in a conference call on Friday that they expect by season’s end, the toll will approach, if not exceed, the 148 pediatric deaths reported during the 2014-15 season.

They noted that hospitalization rates for people between 50 and 64 years old have also been unusually high this season, which could cause some strain on the economy because many people in that age range tend to hold higher-paying managerial roles.


Some parts of the country, particularly the West Coast, have been hit hard by the flu so far, while other areas, such as the Northeast, are beginning to catch up, Dr. Daniel B. Jernigan, director of the CDC’s influenza division, said according to a transcript of the call with reporters Friday.

The timing and duration of the flu season varies each year. Historically, the most common month for flu activity to peak has been February, which could suggest that the worst is yet to come.

But as officials have suggested, this flu season got off to an earlier start than normal and it can be hard to predict when it will start to taper off.

US Centers for Disease Control and Prevention
US Centers for Disease Control and Prevention

Matt Rocheleau can be reached at matthew.rocheleau@globe.com. Follow him on Twitter @mrochele.