Flu season is coming. The U.S. Centers for Disease Control and Prevention and local doctors recommend getting flu shots by Halloween — sometimes known as the "Say Boo to the Flu" campaign.

The severity of flu season is difficult to predict, said Dr. Brian Metzger, medical director of infectious diseases at St. David's HealthCare, but "we're due for a little bit of a larger season," he said.

The flu didn't circulate at a wide level the past two years, which means we have a higher number of people who don't have the immunity and could be more susceptible to it, he said.

Last flu season was delayed, but we saw a spike in cases in the spring, in part because people started socializing again and stopped wearing masks, some doctors say.

"We pushed it off," Dr. Ryan McCorkle, an emergency room physician at St. David's Medical Center, said in the spring. "We saw some (cases), but not very many."

McCorkle said in April that his emergency room was seeing 10 cases of flu to every one case of COVID-19. 

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The CDC releases weekly flu surveillance reports. For the week ending Sept. 17, it noted that Texas had a moderate number of cases. Most of the rest of the country had a low or minimal case rate.

In recent weeks, Travis County has been seeing some influenza A and B strains. Surrounding counties have seen flulike illnesses mostly, according to the Texas influenza activity map. Austin Public Health will begin its flu surveillance Oct. 1.

Immunologists are looking at the flu season in Australia to predict what ours will be like. During our summer, Australia had that country's worse flu season in five years. Those cases have hurt children and teens especially. Flu, in general, moves from Asia and Australia to Europe and then to North America.

Flu symptoms include cough, congestion, vomiting, diarrhea, fatigue, aches and fever.  Those are the same symptoms that can come with other respiratory viruses, including COVID-19 and respiratory syncytial virus.

Call your doctor to be tested to see which virus you have. Then stay at home until you are no longer contagious, typically 24 hours without a fever.

Most people can treat flu at home with over-the-counter cold and flu medications. If they are within the 48-hour window of first symptoms, they can get Tamiflu or a similar medication that can often help shorten the illness.

If they are experiencing severe flu symptoms, the emergency room can help with fluids, anti-nausea or anti-diarrheal medications, breathing treatments or steroids for a cough.

It's all the things we've been doing for COVID-19: Handwashing. Avoiding crowded areas. Getting vaccinated. Staying at home when we're sick.

Mask wearing during cold and flu season in large gatherings might make sense, because "it's a pretty simple precaution," McCorkle said. "No one likes having the flu." 

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Austin Public Health recommends that anyone 6 months or older get a flu shot by the end of October.

"Now is not the time to let our guard down," Austin-Travis County Health Authority Dr. Desmar Walkes said earlier this month. "Everyone, especially children and seniors, need flu protection. This time last year we were fighting the COVID-19 delta variant, and we protected our most vulnerable from COVID-19 and flu with a combination of masking and vaccine. Let’s do it again."

It typically takes about two weeks to reach maximum effectiveness. Flu shots usually are effective for six to nine months.

You can get a COVID-19 vaccination or booster at the same time as your flu shot. COVID-19 vaccinations are free for everyone. Flu shots generally are free for people who have insurance and are available at most pharmacies and primary care physicians' offices.

If you don't have insurance, Austin Public Health has vaccine clinics with reduced rates or even free vaccinations for those who cannot pay. The Far South Clinic, 405 W. Stassney Lane, and the St. John Clinic, 7500 Blessing Ave., are both open from 10 a.m. to 1:30 p.m. and 3 to 7 p.m. Mondays, from 8 a.m. to 12:30 p.m. and 2 to 5 p.m. Tuesdays through Thursdays, and from 8 to 11:30 a.m. Fridays. On the first Saturday of each month, the Far South Clinic is open from 8 a.m. to noon. The third Saturday of the month, the St. John Clinic is open from 8 a.m. to noon. You can make an appointment by calling 512-972-5520. 

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Having the flu weakens the immune system, making it hard to fight the next virus or bacterial pneumonia. That's when people end up in hospitals.

"The flu does take a toll on the immune system," said Dr. Shyam Sivasankar, pediatric emergency medicine physician at St. David's Children's Hospital.

When people have a respiratory illness such as the flu, they could have hypoxia, or less oxygen in the blood. That's hard on the heart, which could affect the heart muscle and trigger a heart attack in adults.

A 2020 study published in the Annals of Internal Medicine looked at adults who were hospitalized for the flu from 2010 to 2017 during flu seasons. One in 8 had what they called "an acute cardiovascular event," such as a heart attack or other sudden heart disease. 

A 2018 study found that people were six times more likely to have a heart attack within a week of having the flu. 

Inflammation from the flu also can cause plaque that has built up in the arteries to break off and trigger a heart attack. People also can experience inflammation of the heart muscle (myocarditis) or the lining around the heart (pericarditis). 

The flu also can weaken the body, causing sepsis or a secondary infection from bacteria or another virus. The elevated stress response of the body trying to fight the influenza virus can weaken the heart muscle. 

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The flu shot is available for ages 6 months and older. Doctors say it is most important for anyone for whom getting the flu would be more likely to become life-threatening. That includes elderly people; anyone who has asthma, diabetes or an immune deficiency; pregnant women; anyone who is morbidly obese; and anyone who is caring for someone with any of these conditions. If there is a vaccine shortage, these are the people who will be given priority to receive a shot.

Check with a doctor if you have a question about whether you can get a flu shot. Children ages 6 months to 3 years sometimes will receive a different form of the shot or half the dosage.

Kids 8 and younger need two shots one month apart the first time they get a flu shot to build up immunity. People ages 9 and up don’t need to get two shots even if they’ve never had a flu shot, said Dr. Leighton Ellis, pediatric department chair for St. David’s Children’s Hospital. The CDC assumes that at some point they’ve been exposed to the flu and have some natural immunity to it if they’ve made it to age 9.

For adults 65 and older, a high-dose flu vaccine is available; it is designed to improve their immunity to the flu. Immunity in older adults starts to wane more quickly, usually around six months. Kids’ immunity lasts 12 to 18 months, and typical adults usually have about 18 months of immunity. (That doesn’t mean adults should skip the shot one flu season because strains of the flu change each year and the shot is for that year’s strains.)

That high-dose vaccine is especially important for people who have had a bad bout of the flu despite getting the flu shot in the past.

The side effects for all of these are similar, and typically it’s irritation at the site of the shot.

Sometimes people who are allergic to eggs have been told not to get a flu shot, but that is no longer true. If you previously had a severe allergic reaction to a flu shot, check with your doctor and have your shot given in a doctor's office, where you can be monitored afterward.

"I can't think of a patient that shouldn't get the flu shot," said Dr. Vivek Goswami, a cardiologist at Austin Heart.

For people afraid of needles, a nasal spray vaccine is available for ages 2 to 49. FluMist, though, is not for everyone. It is a live virus, not the inactive virus in the flu shot. It is not for pregnant people or anyone with asthma, immune suppression or a history of cancer. It also shouldn’t be given with other vaccines.

Ellis shared a few of her tips for getting a shot:

• Use a cold spray or a numbing spray on the area.

• Use the Buzzy Bee (a cold, buzzing device that distracts from the area where pain is being felt) on the arm.

• Blow a breath out at the same time the shot is going in.

• Use electronic devices to distract, such as playing games on a phone.

• Engage in an unrelated conversation during the shot.