Is pneumonia contagious?

What are the risk factors for pneumonia?

• Age under 2. Risk factors in infants include premature birth, zinc or vitamin A deficiency, lack of measles immunization and non-exclusive breastfeeding ^[1].
• Age over 65
• Acute viral infection, such as influenza (the flu) or measles
• Chronic health conditions, such as asthma, chronic obstructive pulmonary disease (COPD), alcoholism, liver cirrhosis, malnutrition, teeth or gum infection (periodontitis), sickle cell anemia, diabetes mellitus, congestive heart failure, weak immunity (HIV/AIDS, removed spleen, cancer, leukemia), neurological diseases with impaired cough reflex, cystic fibrosis or being in wheelchair or bedridden
• Hospital stay, especially when being on a mechanical ventilator in the intensive care unit, or after a major surgery (mainly brain, neck, chest or upper abdominal surgery) ^[33]
• Smoking tobacco ^[4], cocaine (crack) or marijuana (weed) ^[5]
• Drugs: prolonged steroid therapy ^[33,34,35], chemotherapy, immunosuppressant therapy associated with organ transplantation, proton pump inhibitors
• Crowded environments (college dorms, daily care units, nursing homes, military), mostly during winter and early spring (bacterial and viral pneumonia) or late summer or autumn (Mycoplasma pneumonia) ^[30]
• Living near big hospitals or hotels with cooling towers (Legionnaires’ disease)
• Exposure to bird/bat droppings
• Pregnancy ^[2]
• Genetic susceptibility ^[6]
• Other references: ^[1,7,8,9,26]

There is insufficient evidence about low body temperature (hypothermia) ^[10] or exposure to cold and dry air ^[3,11,12,13] as risk factors for pneumonia.

How can you get viral pneumonia?

Viral pneumonia usually develops as a complication of flu, bronchitis or rarely an infection of upper respiratory tract, such as common cold, mainly in young children, older adults and individuals with weak immunity ^[2].

If you are healthy and you are in close contact with someone who has viral pneumonia, you will more likely get the flu or other viral diseas rather than pneumonia ^[2,29].

How can you get bacterial pneumonia?

If you have poor immunity, flu, viral pneumonia or you are in intensive care unit on mechanical ventilation, you can get bacterial pneumonia by inhaling bacteria from your own nose or throat ^[22,26] or by being in prolonged and close (<3 feet or 1 meter) contact with someone who has bacterial pneumonia and coughs and sneezes ^[14,30].

If you are otherwise healthy, it is not very likely you will get pneumonia after being in contact with someone who has bacterial pneumonia ^[17].

Intravenous drug users can get pneumonia from the Staphylococcus aureus bacteria, which normally live on their skin and which–during a drug injection–enter the blood and from there the lungs ^[26].

A spread of the microbes from other infected internal organs (bowel, kidney, liver, heart valves) to the lungs can also cause pneumonia.

How can you get atypical (walking) pneumonia?

You can get atypical pneumonia by inhaling bacteria, such as Mycoplasma pneumoniae or Chlamydophila pneumoniae, when you are in close contact with someone who has atypical pneumonia and coughs and sneezes. Mycoplasma may not be very contagious, but outbreaks of pneumonia in crowded settings can occur ^[18,19].

The bacterium Legionella, which causes atypical pneumonia called Legionnaires’ disease, is not spread from person to person but by aerosolized water from cooling towers, air conditioners, hot tubs, whirlpools and showers, mainly in the buildings with complex water systems, such as hospitals and hotels ^[21]. The infection can occur year round but more commonly during the summer ^[32].

How can you get fungal pneumonia?

Fungi, such as Coccidioides and Histoplasma, which can cause pneumonia, rarely spread among otherwise healthy individuals but you can inhale them from the bird, bat and rat droppings in the soil, especially in the farms in the Mississippi River and Ohio River Valley and southwestern United States ^[25].

If you have a weak immune system, for example, due to HIV/AIDS or chemotherapy, you can get fungal pneumonia by inhaling the fungi, such as Candida, that normally live in your own mouth or from Pneumocystis jirovecii that normally lives in your lungs (opportunistic infection) ^[16,27].

How can you get aspiration pneumonia?

Aspiration means the entrance of fluid or solid material into your lungs. This can happen if you have an impaired gag reflex due to a neurological disease or if you vomit while unconscious, for example, while being severely drunk. When the material you have aspired is contaminated by bacteria (usually from your own mouth), you can develop bacterial pneumonia ^[31].

There is a chance that you get bacterial pneumonia when you are in close contact with someone who has developed aspiration pneumonia and coughs and sneezes.

Rarely, you can get pneumonia after inhaling dust from the skin or feathers of cats, cattle, sheep, goats (Q fever, anthrax pneumonia) or birds (bird flu, psittacosis).

How long does contagiousness in pneumonia last?

It is not known for how long does contagiousness in pneumonia last. In general, a person less likely spreads microbes after the onset of antibiotic treatment or after a drop of high temperature, that is usually after 2-10 days ^[15,24].

Can pneumonia spread from a mother to her baby?

During delivery, a newborn can contract the bacterium Chlamydia trachomatis from the vaginal canal of the infected mother and develop pneumonia ^[20].

Pregnant women are at increased risk of getting pneumonia ^[2]. Some viruses that cause pneumonia in mothers, for example, Influenza A virus (H1N1 – pandemic flu, but less likely H3N2 – seasonal flu) ^[28] , HIV and Varicella-zoster virus (chicken pox), can cross the placenta and cause pneumonia or other complications in the unborn babies ^[23].

• References

  1. Rudan I et al, 2008 Epidemiology and etiology of childhood pneumonia  PubMed Central
  2. Mosenifar Z, Viral Pneumonia, overview  Emedicine
  3. Liu Y et al, 2014, Temporal relationship between hospital admissions for pneumonia and weather conditions in Shanghai, China: a time-series analysis  PubMed Central
  4. Allmiral J et al, 2014, Community-acquired pneumonia among smokers  PubMed
  5. Marijuana: facts for teens  National Institute on Drug Abuse
  6. Waterer GW et al, 2005, Genetic susceptibility to pneumonia  PubMed
  7. Pneumonia  Encyclopaedia Britannica
  8. Pneumonia – What Increases Your Risk  WebMD
  9. Types of pneumonia  National Heart, Lung and Blood Institute
  10. Pio A et al, 2010, Avoiding hypothermia, an intervention to prevent morbidity and mortality from pneumonia in young children  PubMed
  11. Davis RE et al, 2015, Cold, Dry Air is Associated with Influenza and Pneumonia Mortality in Auckland, New Zealand  PubMed
  12. Davis RE et al, 2012, The Impact of Weather on Influenza and Pneumonia Mortality in New York City, 1975–2002: A Retrospective Study  PubMed Central
  13. Davis RE et al, 2015, Cold, Dry Air is Associated with Influenza and Pneumonia Mortality in Auckland, New Zealand  PubMed
  14. Healthcare Infection Control Practices Advisory Committee (HICPAC), Part III: Precautions to Prevent Transmission of Infectious Agents  Centers for Disease Control and Prevention
  15. Davis CP, Is pneumonia contagious?  MedicineNet
  16. Bennett NJ, Pneumocystis jiroveci Pneumonia Overview of Pneumocystis jiroveci Pneumonia  Emedicine
  17. Pneumonia  Kidshealth.org.nz
  18. Lastings DL et al, 2015, Mycoplasma pneumoniae Outbreak in a Long-Term Care Facility — Nebraska, 2014  Centers for Disease Control and Prevention
  19. Mycoplasma pneumonia infection, causes and transmission  Centers for Disease Control and Prevention
  20. Oba Y, Chlamydial pneumonias  Emedicine
  21. Legionella (Legionnaires’ Disease and Pontiac Fever)  Centers for Disease Control and Prevention
  22. Koenig SM et al, 2006, Ventilator-Associated Pneumonia: Diagnosis, Treatment, and Prevention  PubMed Central
  23. Rodriguez J et al, 1992, Pneumonia complicating pregnancy  PubMed
  24. Mycoplasma Infection (walking pneumonia, atypical pneumonia)  New York State Department of Health
  25. Healthcare Infection Control Practices Advisory Committee (HICPAC), 2007 Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings  Centers for Disease Control and Prevention
  26. Kamangar N, Bacterial pneumonia  Emedicine
  27. Mandanas RA, Fungal Pneumonia Overview of Fungal Pneumonia  Emedicine
  28. 2010, Transplacental transmission of influenza virus: What do we know? Bioline International
  29. Falsey AR et al, 2006, Viral Pneumonia in Older Adults  Clinical Infectious Diseases
  30. Mycoplasma Infection (walking pneumonia, atypical pneumonia)  New York State Department of Health
  31. Swaminathan A, Aspiration pneumonitis and pneumonia  Emedicine
  32. Cunha BA, Legionnaires disease  Emedicine
  33. Arozullah AM et al, 2001, Who Gets Pneumonia after Surgery?  Annals of Internal Medicine
  34. McKeever T et al, 2013, Inhaled corticosteroids and the risk of pneumonia in people with asthma: a case-control study  PubMed
  35. Almirall J et al, 2008, New evidence of risk factors for community-acquired pneumonia: a population-based study  European Respiratory Journal