The flu lands hundreds of thousands of people in the hospital each year and kills tens of thousands. But flu that leads to pneumonia is even deadlier.

Startling statistic: Flu-plus-pneumonia ranks eighth in leading causes of death in the US.

THE FLU/PNEUMONIA COMBO

Every year, pneumonia affects more than one million Americans—and about 50,000 die. People most susceptible to pneumonia include the elderly, especially nursing home residents and individuals who have chronic health conditions such as heart or lung disease. The flu-to-pneumonia progression isn’t the only cause of pneumonia, of course, but since the combo is so deadly—and often so preventable—it’s worth special attention.

Here’s what happens: You get the flu, a contagious respiratory illness caused by an influenza virus. You get the typical symptoms—sore throat, cough, body aches, fever, headaches and chills. But the flu also makes your lungs more susceptible to a bacterial infection caused by Streptococcus pneumoniae (S. pneumoniae), the most common cause of pneumonia in adults.

When that happens, air sacs fill with pus and other liquid, making it harder for oxygen to reach the bloodstream and making it difficult to breathe. Death can come from organs that are starved of oxygen—or from a blood infection (sepsis).

Here’s how to protect yourself…

STEP ONE: GET A FLU SHOT

If you don’t get the flu, you won’t be at risk for that combination of flu virus/S. pneumoniae that is so dangerous to susceptible people. Getting a flu shot is the best way to protect yourself. It is recommended for everyone over the age of six months. While not 100% effective, it does offer substantial protection.

Why a flu shot is so important this year: It’s expected to be a worse-than-average flu season. Australia already had its worst flu season on record—and what happens Down Under often happens in North America. A bad flu year means that pneumonia cases could potentially soar. Fortunately, this year’s flu shot is a good match for the kinds of flu viruses coming our way.

STEP TWO: MAKE SURE YOU’RE UP-TO-DATE ON PNEUMONIA VACCINATION

Effective vaccines exist against S. pneumoniae, which, as described earlier, causes the vast majority of pneumonia cases in adults. Everyone age 65 and older should be vaccinated—yet only about 50% of healthy adults in this age group are. Some adults need protection before they turn 65—smokers and anyone with a chronic health condition (heart or lung disease, diabetes, asthma, etc.). For the best protection, you’ll need two different vaccines, spaced out over a year or more…

• Start with a onetime-only dose of the pneumococcal conjugate vaccine called PCV13 (Prevnar 13), which protects against 13 types of pneumococcal bacteria.

• One year later, get a dose of pneumococcal polysaccharide vaccine PPSV23 (Pneumovax), which protects against 23 strains of pneumococcal bacteria. Prevnar 13 primes your immune system so that Pneumovax works better than it would if you took it by itself.

• Based on your age and health, your doctor may advise another dose of Pneumovax five years later.

STEP THREE: WATCH YOUR MEDS

Certain health conditions and medications can affect your susceptibility to pneumonia…

• Steroids and other immunosuppressive drugs can make you more susceptible to pneumonia. These drugs interfere with the immune response, so your body can’t fight off infection as easily.

Low-dose steroids, even taken long-term, may not increase pneumonia risk, but higher doses (such as 20 mg a day) can do so in as little as two weeks. If you need a high-dose steroid to control your condition, be especially vigilant during flu season—get vaccinated, wash your hands frequently, stay away from crowds, and call your doctor at the first sign of illness such as a sore throat.

• Acid-suppressive medications, such as proton pump inhibitors including omeprazole (Prilosec), as well as histamine-2 receptor antagonists including ranitidine (Zantac), inhibit the production of stomach acids. But these acids help keep harmful gut bacteria in check.

Less acid means more potential for harmful bacteria to colonize and eventually enter the lungs. Unless your doctor prescribes these on a long-term basis (a rare occurrence), use them only for short periods of time—no more than four weeks for heartburn/gastroesophageal reflux disease (GERD), for example.

• Pneumonia occurs less often in adults who get routine dental checkups. Routine dental visits can help decrease the overall amount of bacteria in your mouth, including those that can cause pneumonia in susceptible people. Bonus: A healthy mouth reduces heart disease risk, too.

IF YOU DO GET THE FLU…

Since the flu shot doesn’t always prevent infection, be on the lookout for symptoms including feeling feverish, chills, body aches, sore throat and fatigue. If you suspect that you have the flu, call your doctor. You may be a candidate for prescription antiviral medication such as oseltamivir (Tamiflu), which can shorten your illness duration and possibly decrease the odds of it progressing to pneumonia. But you need to take it within a day or two of the first symptoms for it to be effective.

PNEUMONIA AND YOUR HEART

Adults hospitalized with pneumonia have a heightened risk for cardiovascular problems including sudden heart attack, often with no warning signs. What happens: Oxygen deprivation from a bout of pneumonia can starve cardiac muscle cells so that they function less well or even die off. One study found that within the first month of pneumonia diagnosis, the risk for stroke, heart attack or death due to heart disease grew by as much as fourfold…and remained elevated for years. Patients recovering from pneumonia also are predisposed to developing it again—another good reason to prevent it in the first place.