everything to know about pneumonia

Hollywood icon Diane Keaton died after a battle with pneumonia, her family confirmed late Wednesday.

Sources close to the Oscar-winning actress said her health took a dramatic turn in the months before her death at the age of 79 on Saturday.

Here’s everything you need to know about the common — but potentially deadly — illness that claimed her life.

What is pneumonia?

It’s a lung infection that causes the air sacs to swell and fill with fluid or pus, making it hard to breathe and easy to get dangerously sick.

It’s a common condition, affecting about 25 out of every 10,000 adults in the US, with rates increasing significantly as people age. That amounts to millions of cases annually.

What causes pneumonia?

Pneumonia can be caused by several organisms, but the biggest culprits are viruses and bacteria, according to the American Lung Association.

Viral pneumonia usually comes from bugs like the cold, flu, COVID-19 or RSV. Most cases are mild and clear up faster than bacterial pneumonia — but some can become severe.

Bacterial pneumonia can strike on its own or follow a viral infection, and it’s generally more common and serious than viral pneumonia. The leading cause is a bacteria called Streptococcus pneumoniae (pneumococcus), which normally lives in the upper respiratory tract.

While pneumonia itself isn’t contagious, the viruses and bacteria that cause it are. You can pick them up by touching infected surfaces or breathing in droplets from coughs and sneezes.

Fungus can also cause pneumonia, although it’s a much less common source. It’s usually acquired by inhaling fungal spores from the environment, rather than from contact with an infected person.

Who’s at risk?

Pneumonia can affect anyone, but the most vulnerable are kids under 2 and adults over 65 due to their weak or aging immune systems, according to the Mayo Clinic.

People with compromised immune systems — like those with HIV/AIDS, cancer patients on chemo or radiation or organ transplant recipients — also face a higher risk. The same goes for anyone recovering from a recent respiratory virus.

If you’re staying in the ICU or on a ventilator, your chances of being diagnosed increased.

Lifestyle habits can affect your chances, too. Smoking and heavy drinking make you more vulnerable, as does breathing in pollution or toxic fumes.

What are the symptoms?

Bacterial pneumonia can hit suddenly or creep in slowly. It can cause:

• High fever
• Fatigue
• Shortness of breath
• Rapid heartbeat
• Chills
• Chest or stomach pain
• Loss of appetite
• Cough that brings up yellow, green or bloody mucus .

Viral pneumonia usually develops over several days. It can cause:

• Fever
• Dry cough
• Headache
• Muscle aches
• Extreme fatigue

Babies and young children may not show typical signs. Instead, look for trouble feeding, nonstop crying, limpness, pale skin, noisy breathing, vomiting, fussiness or coughing.

Is pneumonia deadly?

It’s the top reason that US children end up in the hospital, and for adults, its the second leading cause of hospital stays — trailing only behind childbirth, according to the American Thoracic Society.

Some cases are mild, but pneumonia can be brutal. Recovery can take weeks, and complications like respiratory failure, fluid buildup, lung abscesses and bloodstream infections can turn deadly.

Every year, about 1 million adults in the US land in the hospital with pneumonia — and roughly 50,000 don’t survive.

Can you prevent it?

Vaccines are one of the best defenses against pneumonia. Shots targeting the bacteria and viruses that cause the infection can lower your risk of getting it, and if you do get sick, they can help keep it from turning severe.

Beyond vaccines, simple healthy habits help, including quitting smoking, cutting back on booze, eating right, exercising and getting plenty of rest.

Treat any other infections or health issues that could weaken your immune system is also a crucial part of staying ahead of pneumonia.