“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? Plus, what are the symptoms of pneumonia and how do you know if you have it?

Below, we answer all these questions and more.

What is pneumonia exactly?

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 your pneumonia.

Types and causes of pneumonia

The types of pneumonia are categorized based on what caused it, and there are more than 30 causes of pneumonia. Pneumonia can also be differentiated by how long you’ve been sick and how many cases of pneumonia you’ve had in a certain span of time.

Viral pneumonia

Viral pneumonia is – you guessed it – 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 COVID-19, which can be very serious.

COVID-19 pneumonia

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 those of other types of viral pneumonia, but pneumonia caused by COVID-19 is often serious and can worsen rapidly. Many cases may require hospitalization.

Bacterial pneumonia

Bacterial pneumonia is the most common form of pneumonia and can be the most severe. It’s caused by breathing in bacteria, and 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 can 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.

Aspiration pneumonia

Aspiration pneumonia is caused by accidentally inhaling liquids or solids – food, drink, vomit or saliva – into your lungs instead of swallowing or expelling them. The inhaled material then causes inflammation and infection in the lungs. This type of pneumonia often affects those with a form of cognitive impairment, whether due to a traumatic brain injury, disability or substance use disorder. It also affects the elderly and people with health conditions that affect swallowing, like stroke.

Fungal pneumonia

Fungal pneumonia is a rare but often serious type of pneumonia. It’s acquired by inhaling the fungal spores of certain fungus species that live mostly in the soil but can also be found in other indoor and outdoor settings, including the hospital. These spores then cause a fungal infection in your lungs. To treat you with the correct antifungal regimen, your doctor will need to determine exactly where you picked up the fungus that made you sick. Different species of fungus inhabit different regions in the U.S., and each requires a specific treatment.

Walking pneumonia

Walking pneumonia, also known as atypical or mycoplasma pneumonia, is a form of pneumonia known for its comparatively minor symptoms. It’s caused by the bacteria Mycoplasma pneumoniae and seen mostly in kids and adults under 40. Because walking pneumonia is so mild, many people don’t realize they have it. They’ll continue their daily activities – like going to work and school, and “walking” around (hence the name) – thinking they have a regular cold. Walking pneumonia can be easily spread in this way.

Health care-associated and community-acquired pneumonia

Based on where you caught your pneumonia, your doctor will categorize it as health care-associated pneumonia (HCAP) or community-acquired pneumonia (CAP). If you were hospitalized, stayed at a long-term care facility, or visited a dialysis center for treatment within the last three months, your pneumonia is likely health care associated. If not, then your pneumonia is community acquired. This distinction helps your doctor prescribe the right antibiotics.

Chronic and recurrent pneumonia

Any type of pneumonia can be chronic or recurrent – it depends on how long and how often you’ve had it. Pneumonia is considered chronic when symptoms persist for longer than six weeks. Pneumonia is considered recurrent if you have two cases in a single year, or if you’ve had pneumonia more than three times over your life.

Most types of pneumonia are contagious, but not all

Both viral and bacterial pneumonia are contagious because the virus or bacteria can spread from person to person, qualifying them as infectious diseases. 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 handwashing habits.

But not all types of pneumonia are spread so easily. For example, fungal pneumonia passes from the environment to people (transmitted through inhalation of fungal spores), but won’t pass 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 on someone else.

Your pneumonia symptoms can depend on the type of pneumonia you have, with bacterial pneumonia bringing on the most serious symptoms. Pneumonia symptoms can range from mild to severe and may include:

  • Rapid heartbeat and shortness of breath
  • Coughing, often clearing yellow or green mucus from the lungs
  • Feeling weak or overly tired
  • Fever accompanied by chills, shaking and sweating
  • Sharp, stabbing chest pain, especially when breathing in or coughing
  • Nausea and/or vomiting, commonly seen in infants or young children
  • Confusion, especially among people older than 65
  • Diarrhea

Can you really “catch pneumonia” from cold or wet conditions?

The short answer is no. Viruses and bacteria are the real culprits. But keep in mind – 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 snowstorm and get soaked in the spring puddles? Perhaps rely on a time-tested phrase from your parents’ playbook: Everything in moderation.

Diagnosing pneumonia

If you think you have pneumonia, make an appointment with your primary care doctor. You can also visit urgent care if needed. Because there are so many types of pneumonia, and the symptoms can vary so much from one person to the next, your doctor has to be thorough when diagnosing your pneumonia. Your doctor will use these three key factors to diagnose pneumonia:

Medical history

To determine where and why you got pneumonia and whether it’s viral, bacterial or fungal, your doctor will ask you questions about:

  • Your job
  • Recent or chronic illnesses, and whether you were hospitalized
  • Recent trips you took both inside and outside the U.S.
  • Recent contact with anyone who seemed sick
  • Recent exposure to animals, especially birds

Physical exam

Your doctor will perform a physical exam during the diagnostic process for pneumonia. They’ll listen to your lungs with a stethoscope and, if you have pneumonia, they might hear a crackling, bubbling or rumbling sound as you inhale. They will also check for a blue tint to your lips or fingernail beds, which tells them you’re not getting enough oxygen.

Diagnostic testing

Your doctor may conduct the following tests to determine whether you have pneumonia, as well as the type and severity:

  • Chest X-ray – If you have pneumonia, a chest X-ray will show the area and pattern of inflammation and infection in your lungs.
  • Blood test – Your doctor may order one or more blood tests to gather more information about your type of pneumonia.
  • Blood oxygen measurements – Pneumonia prevents oxygen from spreading throughout your body by way of your blood. Using a small device called a pulse oximeter clipped to your finger, your doctor can measure the level of oxygen in your blood.
  • Sputum test – If you’ve been coughing up mucus, your doctor may take a sample for testing.

Ways to 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 – Pneumococcal vaccines are available to offer protection from many types of bacterial pneumonia, as well as meningitis and sepsis. However, this vaccine can’t prevent other types of pneumonia. Consult your doctor or your child’s pediatrician for information on the best vaccine and the best timing for you and your family. And make sure to get your flu shot every year, as the flu can be a common cause of pneumonia.
  • Don’t smoke – Smoking harms your lungs and hinders your immune system’s ability to fight respiratory infections.
  • Practice good 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. If someone in your home has just recovered from pneumonia, give common areas like the bathroom and kitchen a deep, disinfecting clean.

Pneumonia treatment and when to get immediate medical attention

If you have pneumonia, your doctor may send you home with a prescription for antibiotics and instructions to aid in your recovery, like getting plenty of rest, drinking fluids and taking over-the-counter pain relievers and fever reducers. Don’t take cough suppressants, as coughing helps empty your lungs of fluid and mucus.

Most people get better from pneumonia in about 2-4 weeks. However, certain people are more susceptible to becoming seriously ill. The following groups have the most risk of catching pneumonia and may require more intensive pneumonia treatment at the hospital:

  • 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 those with an autoimmune disease, HIV/AIDS or people undergoing chemotherapy

If you’ve been recovering at home, call your doctor right away or visit urgent care if you have:

  • Some difficulty breathing
  • A persistent fever of 102 degrees Fahrenheit (39 degrees Celsius) or higher
  • Severe chest or stomach pain
  • An ongoing cough, especially if you start coughing up bloody mucus
  • Symptoms that haven’t improved after 2-3 days of taking antibiotics
  • Worsening symptoms

Head to the emergency room or call 911 right away if someone with pneumonia is:

  • So short of breath that they’re gasping and can’t speak
  • Suddenly confused and disoriented
  • Exhibiting blue-tinged lips, tongue, fingers or other areas of skin

Stay well in any weather

Though pneumonia is often associated with fall and winter, it can also strike in the summer months. That’s why it’s important to practice pneumonia prevention year-round: wash your hands frequently, stay up to date on your vaccinations and the yearly flu shot, and keep your immune system strong with a healthy diet and regular exercise. But if you find yourself or a family member coming down with pneumonia, we’re here to help.