Reports of influenza-like illness are on the rise in Massachusetts and across most of the United States, as what is typically the peak of flu season approaches.
Rates of reporting of influenza-like illness — defined as having a fever of over 100 degrees Fahrenheit and a cough, sore throat, or both — were highest in a cluster of suburbs west of Boston roughly between the I-95 and I-495 belts and in the western part of the state, as of the week ending Jan. 21, the latest data from the state Department of Public Health.
Sandwiched between those two regions, communities in central Massachusetts and metro Boston had lower reports of influenza-like illness.
Statewide, the 2016-17 flu season so far has seen higher rates of influenza-like illness reports and higher rates of hospitalization than last year’s season, but lower rates than two seasons ago, data show.
Though the timing of flu is unpredictable and can vary season to season, state officials said the worst is likely yet to come, as flu activity tends to peak in February.
“Over the last few weeks we’ve seen increased activity . . . [and] we expect it to pick up and peak in the next couple of weeks,” said Dr. Al DeMaria, state epidemiologist and medical director of the state’s Bureau of Infectious Disease and Laboratory Sciences.
“We’re still waiting for it to take off, but it’s definitely high enough now to tell us we’re into the flu season,” he added.
Last season, 2015-16, flu activity peaked later than usual, in March.
The year before that, the 2014-15 season, saw high numbers of people infected with the illness, which experts said they believed was related to a flu vaccine that turned out to be a poor match for the virus in circulation that season.
(Each year, months before the start of the flu season in the United States, health authorities examine which strains are circulating elsewhere in the world and make their best judgment about the types of flu likely to strike and include those strains in that year’s vaccine. It can take several months to produce large quantities of influenza vaccine.)
This year, “so far, it looks like it’s a good match,” said DeMaria, noting that it’s still early in the season.
At best, vaccination reduces the risk of contracting the flu by about 50 to 60 percent, recent studies have shown, according to the Centers for Disease Control and Prevention.
“It’s still the best thing you can do to protect yourself,” DeMaria said.
And, “it’s not too late to get a flu shot.”
Officials said that people who haven’t been vaccinated already can contact their health care provider, local board of health, or nearby pharmacy to get vaccinated.
Nationwide, influenza activity was considered to be “widespread” in 37 states, including Massachusetts, as of the week ending Jan. 21, the latest data tracked by the CDC.
The flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs, the CDC says. Symptoms can include fever or feeling chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, and fatigue.
It can cause mild to severe illness, and can lead to death, officials say.
Each year, the flu sickens millions of people in the United States, sending hundreds of thousands of them to hospitals, and thousands, if not tens of thousands, die, the CDC says.
People most at risk for serious complications include young children, pregnant women, people 65 years and older, and people with chronic medical conditions, such as asthma, diabetes, or heart disease.
The best way to prevent catching the virus is to get a flu vaccination each year, the CDC says.
The agency also recommends staying away from people who are sick, covering coughs and sneezes, and frequent handwashing.