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Refers to pneumonia caused by a virus.
Viral pneumonia occurs in about 200 million people a year which includes about 100 million children and 100 million adults.
Viruses are one of the two major causes of pneumonia, along with bacteria.
Less common causes of pneumonia are fungi and parasites.
Viruses are the most common cause of pneumonia in children.
Bacterial infection is a more common cause of pneumonia in adults.
Viral pneumonia symptoms include: fever, non-productive cough, runny nose, and systemic symptoms of myalgia, and headache.
Symptoms vary with different viruses.
Common causes of viral pneumonia are:
Influenza virus A and B.
Respiratory syncytial virus.
Human parainfluenza viruses, in children.
Less common viruses causing pneumonia are:
Adenoviruses
Metapneumoviruses
Severe acute respiratory syndrome virus-SARS coronavirus
Middle East respiratory syndrome virus-MERS coronavirus.
Hantaviruses
Viruses that primarily cause other diseases, but sometimes cause pneumonia include:
Herpes simplex virus (HSV)
Varicella-zoster virus (VZV)
Measles virus
Rubella virus
Cytomegalovirus (CMV)
Smallpox virus
Dengue virus
The most commonly identified agents of pneumonia in children are respiratory syncytial virus, rhinovirus, human metapneumovirus, human bocavirus, and parainfluenza viruses.
Usually, a virus will reach the lungs by traveling in droplets through the mouth and nose with inhalation.
Most respiratory viruses are spread via aerosol transmission or airborne particles, less than five μM that remain suspended in air, bypass surgical masks, and directly access the lower respiratory tract via inhalation, and are typically not spread by short-lived, respiratory droplet or by fomites.
The virus then invades the cells lining the airways and the alveoli.
The viral invasion often leads to cell death either through direct killing by the virus or by self-destruction through apoptosis.
Viruses invade cells in order to reproduce.
Additional damage to the lungs occurs when the immune system responds to the infection, as white blood cells activate a cytokines which cause leaking of fluid into the alveoli.
Bacterial pneumonia often complicates viral pneumonia.
The best prevention against viral pneumonia is vaccination against influenza, adenovirus, chickenpox, herpes zoster, measles, and rubella.
Viral pneumonia where influenza A or B are thought to be causative agents, may benefit from treatment with oseltamivir or zanamivir.
Respiratory syncytial virus (RSV) has no specific treatment, but ribavirin in indicated for severe cases.
Herpes simplex virus and varicella-zoster virus infections are usually treated with aciclovir, and ganciclovir is used to treat cytomegalovirus.
There is no known effective treatment for pneumonia caused by SARS coronavirus, MERS coronavirus, adenovirus, hantavirus, or parainfluenza pneumonia.
Viral pneumonia care is mainly supportive.