From the WebMD Archives

April 2, 2019 -- Spring is here, but flu season remains and is probably going to last several more weeks, the CDC says. It has issued a health advisory, reminding doctors that flu activity remains high in the U.S.

As of March 23, flu activity was widespread in 34 states and Puerto Rico.

"While the latest FluView Influenza Surveillance Report showed that influenza activity has decreased since the previous week, flu activity remains relatively high for this time of year, '' says Fatimah S. Dawood, MD, a pediatrician and medical officer in the CDC's influenza division.

The influenza A (H3N2) viruses have been reported more often than the A (H1N1) pdm09 viruses for the past 3 weeks across the country, she says, although other A and B viruses are also causing illness.

From October to mid-February, the H1N1 viruses were predominant, but since late February, H3N2 viruses have become more common.

The influenza A (H3N2) viruses may be associated with severe disease in adults age 65 and up, the CDC says, so antiviral medications should be started in them and other high-risk people as soon as possible after illness begins, without waiting for laboratory confirmation, Dawood says.

Early estimates suggest this year's flu vaccine, overall, is about 47% effective, Dawood says. It is generally less effective against the influenza A (H3N2) than other virus types.

As a result of continuing flu cases, doctors are reminding people it's not too late to get the vaccine. "We are told to vaccine through the spring because the cases keep coming," says Len Horovitz, MD, a pulmonologist at Lenox Hill Hospital, New York. "People think the flu virus has to come in cold weather," he says. But this year, ''flu season is not tapering off as many people expect by March or April."

The CDC reports an increasing number of influenza A (H3N2) cases, as well as continued circulation of influenza A (H1N1) viruses, and low levels of influenza B viruses.

From October to mid-February, H1N1 was predominant, but since late February, H3N2 has become more common.

The flu vaccine is generally less effective against the influenza A (H3N2) than other virus types.

This year's season ''started a little bit later," Horovitz says. But "there is no [set] finish line to the flu season and no starting line."

As of March 23, the CDC has received reports of more than 15,000 laboratory-confirmed hospitalizations due to flu and 77 flu-related pediatric deaths for the 2018-2019 season.

If Flu Strikes

If flu strikes, antiviral medications are recommended by the CDC regardless of whether a person got a flu shot. The antivirals reduce illness and severe complications, research shows. Most people with the flu have mild illness and do not need medical care or antiviral drugs. The CDC says if you get sick with flu symptoms, in most cases, you should stay home and avoid contact with other people except to get medical care. If, however, you have symptoms of flu and are in a high-risk group, or are very sick or worried about your illness, contact your doctor.

The medicines work best when treatment is started early, within 48 hours of symptoms starting.

Some studies have shown a benefit to starting the antivirals for patients who are hospitalized or young children with fevers if the medicine is started even 3 to 5 days after symptoms begin, some research suggests.

Four antivirals are approved by the FDA for use during the 2018-2019 flu season. They are:

  • Oseltamivir phosphate (generic or Tamiflu)
  • Inhaled zanamivir (Relenza)
  • Intravenous peramivir (Rapivab)
  • Baloxavir marboxil (Xofluza)

Not Too Late to Vaccinate

"I would tell people to still get vaccinated at this point in time," says Aaron Glatt, MD, chair of medicine and hospital epidemiologist at South Nassau Communities Hospital in Oceanside, NY.

For those who got vaccinated very early in the season, is a second vaccination a good idea? "I don't normally tell people to get a second," Glatt says. But he tells high-risk patients (or their parents) to ask their doctor about that.

Among those at high risk for flu are:

  • Adults age 65 and older
  • Children younger than 5, and especially under age 2
  • Those with asthma or other lung problems
  • Those with cardiovascular conditions (except high blood pressure alone)
  • Those with other chronic conditions (kidney, liver, or blood disorders; diabetes; brain disorders; spinal cord problems; or peripheral nerve issues)
  • Those with cerebral palsy, epilepsy, stroke, intellectual disability, developmental delay, or muscular dystrophy
  • Those with a suppressed immune system
  • Those younger than age 19 on long-term aspirin therapy
  • American Indians and Alaska Natives
  • Those with a body mass index (BMI) above 40
  • Residents of nursing homes or other chronic care facilities
WebMD Health News Medically Reviewed by Neha Pathak, MD on April 02, 2019


Fatimah S. Dawood, MD, pediatrician and medical officer, CDC influenza division.

Morbidity & Mortality Weekly Report: "Interim Estimates of 2018-19 Seasonal Influenza Vaccine Effectiveness—United States, February 2019."

CDC Health Advisory: "CDC reminds clinicians to have a high suspicion for influenza and recommends rapid antiviral treatment of high-risk patients with suspected influenza."

CDC FluView, March 23, 2019.

Len Horovitz, MD, pulmonologist, Lenox Hill Hospital.

Aaron Glatt, MD, chair of medicine and hospital epidemiologist, South Nassau Communities Hospital, Oceanside, NY.

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