“Come inside or you’ll catch pneumonia!” Sound familiar? From your childhood you might recall your parents or grandparents yelling this phrase out the door to call you in from the cold or rain. But what exactly is pneumonia? And is it true that cold, wet weather can make you sick?

As you decide whether to let your own kids run through puddles, here are some facts about pneumonia to help us understand it better.

What is pneumonia?

Pneumonia is a common lung infection that causes inflammation in the air sacs of one or both of your lungs. The air sacs may fill up with fluid or mucus, leading to symptoms like chest pain, trouble breathing, fever and cough (often with phlegm).

Symptoms of pneumonia can range from mildly uncomfortable to severe, sometimes requiring hospitalization. How your body reacts greatly depends on your age, your overall health, the strength of your immune system, and the type of germ that caused the infectious disease.

Types of pneumonia and treatment

Viral pneumonia

Viral pneumonia is the most common form, and – you guessed it – it’s caused by a virus. Children and seniors catch it most often. It’s usually mild, but in some cases it can become severe. Rest and hydration are the best treatments, but antibiotics may also be used to avoid related bacterial infections. Doctors can also recommend over-the-counter medications to reduce symptoms of fever, aches and chest pain.

Viruses that can cause pneumonia include the common cold, influenza and Coronavirus 2019 (COVID-19), which can be very serious. We’ll talk more about that in a minute.

Bacterial pneumonia

Bacterial pneumonia is caught by breathing in bacteria. It’s easier to catch bacterial pneumonia after having a cold or the flu because your immune system is weaker from being sick. Other health issues like cancer, diabetes and asthma can also make it easier to catch.

Doctors primarily treat bacterial pneumonia with antibiotics, which are able to target the specific type of bacteria that caused the infection. They may also prescribe medications to help you breathe better, or suggest over-the-counter medicines to improve other symptoms, like fever and chest pain.

Symptoms of pneumonia

Symptoms can range from mild to severe and may include:

  • Quick heartbeat and shortness of breath
  • Coughing, often clearing mucus from the lungs
  • Feeling weak or overly tired
  • Chills
  • Chest pain, especially when breathing in
  • Nausea and/or vomiting
  • Diarrhea

Is it contagious?

Yes, many types of pneumonia are contagious. Both viral and bacterial pneumonia are contagious because the virus or bacteria can spread from person to person. Similar to the way influenza spreads, pneumonia germs can be transferred through coughs and sneezes that aren’t covered, touching contaminated surfaces, sharing drinks or utensils, and not practicing good hand washing habits.

But not all types of pneumonia are spread so easily. For example, fungal pneumonia is a more rare type that can pass from the environment (usually found in soil) to a person, but is not contagious between people. And as for those types that are contagious between people – it’s not always a sure thing. Due to our diverse immune systems, a germ that makes one person sick might not have the same effect someone else.

Those at higher risk for pneumonia include:

  • People over 65
  • Children under 2
  • Pregnant women
  • Smokers
  • People with underlying health conditions, like asthma, diabetes, lung disease or heart disease
  • People with weakened immune systems, including people with an autoimmune disease, HIV/AIDS or people undergoing chemotherapy
  • People who are hospitalized

What is walking pneumonia?

Walking pneumonia is a milder form of pneumonia known for its comparatively minor symptoms. Many people don’t realize they have it, so they’re out walking around (hence the name) and going to school or work like it’s a regular cold. Walking pneumonia is seen mostly in kids and adults under 40. Whether it’s viral or bacterial walking pneumonia, doctors can usually help clear it up in about a week.

When should you see a doctor?

Your primary care doctor can diagnose you with pneumonia after a physical exam. A chest X-ray might also be taken to give a clearer picture of your lungs. Call your doctor if you have:

  • Difficulty breathing
  • Persistent fever of 102 F (39 C) or higher
  • Chest pain
  • An ongoing cough, especially if you’re coughing up mucus
  • Symptoms that are getting worse

If you are in a high-risk group, it’s especially important to contact your doctor, as pneumonia can quickly develop into a life-threatening condition.

How can you prevent pneumonia?

The best way to prevent pneumonia is to build up strong immune defenses and practice good hygiene.

  • Strengthen your immune system – Fortify your immune system by getting enough sleep, eating a healthy diet and exercising regularly.
  • Get vaccinated (kids too) – Vaccines are available to help offer protection from some types of pneumonia and the flu. Consult your doctor or your child’s pediatrician for information on the best vaccine and timing for you and your family.
  • Don’t smoke – Smoking harms your lungs and hinders your immune system’s ability to fight respiratory infections.
  • Hygiene – If you’re feeling sick, stay home. Cover coughs and sneezes with your elbow, and avoid touching your face as much as possible. Wash your hands regularly with soap and water, or use an alcohol-based hand sanitizer if water is not available.

Can COVID-19 cause pneumonia?

Yes, complications from the COVID-19 virus can include pneumonia. COVID-19 is an infection of the upper respiratory tract that can cause inflammation and damage to the small air sacs in your lungs, called alveoli. Pneumonia can develop as a complication of COVID-19 when those air sacs become infected and fill up with fluid and mucus, causing chest pain, coughing and difficulty breathing.

Symptoms of COVID-19 pneumonia are similar to other types of viral pneumonia. Research shows that most people with COVID-19 who get sick experience mild or moderate COVID-19 symptoms that can be treated at home. However, some cases can be severe and require hospitalization.

So can cold or wet conditions really make you sick?

The short answer is no. Viruses and bacteria are the real culprits. But before you call up your parents or grandparents to tell them the news – there does seem to be evidence that some types of environmental stress can weaken our immune systems.

Studies have shown that lower temperatures may have a negative effect on the body’s immune response to fight disease. Additionally, breathing in cold air causes blood vessels in our upper respiratory tract to constrict in an effort to conserve heat. This might keep white blood cells from successfully reaching the mucous membrane to defend against germs.

So does this mean your kids can play outside in a snow storm and get soaked in the spring puddles? Perhaps rely on another time-tested phrase from your parents’ playbook: Everything in moderation.