WASHINGTON — How bad is the flu this year? Media reports of deaths and potentially ineffective vaccines may indicate this is an especially dangerous flu season.

Just last week, California registered its 42nd flu-related death among people under the age of 65, according to reports. Nationwide, the federal government has reported that at least 20 children have died from influenza this season.

It’s too early to say how the 2017-2018 flu season compares to past seasons, Daniel Jernigan, a federal public health official, told attendees at a Tuesday session providing an overview of the current flu season.

Jernigan, the influenza division director of the Centers for Disease Control and Prevention’s National Center for Immunization and Respiratory Diseases, predicted a moderate- to high-severity flu season. But as of now, he said, it’s no worse than other bad flu seasons, including 2014-2015.

So what makes this year different?

One factor may be the reach of the illness. According to CDC, every U.S. state except Hawaii is now reporting “widespread” flu activity, the highest level on a scale that begins with “no activity” at the low end. That’s as of the first week of this year, the most recent for which CDC provides data.

(Centers for Disease Control and Prevention)

That’s a noticeable hike since the first week of the current flu season, which began last October. Most states during that initial week reported sporadic flu activity, and several reported no activity.

(Centers for Disease Control and Prevention)

“Certainly the virus is more widespread this year, specifically at this time,” Kristen Nordlund, a CDC spokesperson, said in an email.

According to Jernigan, the flu season is peaking earlier this year than it did last year. But there is still plenty of time left to get sick, which is why experts highly recommend getting flu shots.

Influenza has several different strains. The two most common in the United States are H1N1 and H3N2. An unusual H1N1 strain was responsible for the 2009 “swine flu” pandemic. But H3N2 is the nastier of the two, and it’s this year’s predominant strain.

The H3N2 strain is associated with more hospitalizations and more deaths than H1N1, particularly among children and older adults. CDC only requires state health departments to provide data on pediatric influenza-related deaths, of which there were 20 in the U.S. as of Jan. 6.

But that data offers only a fragmented picture for health officials, especially since the season is relatively early on. Last flu season – also an H3N2 season – the U.S. saw 110 reported pediatric influenza-related deaths, while 148 were reported in the 2014-2015 season.

As for hospitalizations, the current rate of influenza-related hospitalizations reported by CDC is 22.7 per 100,000 people. That’s consistent with past H3N2 seasons, according to Jernigan.

H3N2 is also more erratic than other strains in how it evolves biologically, according to experts, which makes it more difficult to develop an effective vaccine for it.

But that doesn’t mean the flu vaccine is ineffective.

Some reports have noted that in Australia – which has an earlier flu season and is used as a benchmark to predict trends in the U.S. – the flu vaccine was less effective this year than in past years. But the U.S. has a predominant H3N2 strain that’s different from the predominant one in Australia, David Wentworth, chief of virology, surveillance, and diagnosis in the NCIRD’s influenza division, said during the Tuesday session.

No matter what, though, the take-home message from public health experts is pretty simple: Get vaccinated.

Even if the vaccine is only 30 percent effective – which is about what CDC predicts this year – it is still significantly better than nothing, said Preetha Iyengar, a supervisory epidemiologist at the District of Columbia’s Department of Health. She added that people who are vaccinated tend to contract less severe cases if they become infected than people who aren’t vaccinated.

“There’s still a lot of flu season left to go,” said Iyengar, who noted that it’s also important to take preventive measures like washing your hands and staying home from work or school when you’re sick.

Still, she said, “The number one thing is vaccination.”