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Influenza May Lead to Viral Pneumonia

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Pneumonia related image Photo: Getty Images

Pneumonia is a lung infection that causes difficulty in breathing, with cough and fever. The National Institutes of Health provide details on their PubMed web site. The infection can be caused by a variety of pathogens, including viruses, bacteria, and fungi. Bacterial pneumonia is usually the most serious type, and is treated with antibiotics. However, viral pneumonia can also cause serious illness and death.

Ordinary cases of influenza (the flu) can progress to pneumonia. Dr. Jordi Rello of University Hospital, Tarragona, Spain, and Dr. Aurora Pop-Vicas of Memorial Hospital of Rhode Island, Pawtucket, Rhode Island, provided a review.

Uncomplicated influenza is characterized by inflammation and fluid accumulation in the larynx, trachea, and bronchi. Severe infections can spread deep into the lungs, with damage to the bronchial mucosa, capillaries, and alveoli (air sacs). Autopsies show heavy viral loads in the periphery of the lungs in patients who died of influenza pneumonia.

During a flu epidemic, pneumonia and acute respiratory distress syndrome account for most of the severe illness and death attributed to the influenza infection. Rello and Pop-Vicas wrote, “Pneumonia may occur as a continuum of the acute influenza syndrome when caused by the virus alone (primary pneumonia) or as a mixed viral and bacterial infection after a delay of a few days (secondary pneumonia).”

Lab tests are needed to determine the type of pathogen, so that appropriate drugs can be prescribed. Chest X-rays show extensive fluid in the lungs. Computed tomography (CT) scans can help clinicians distinguish viral pneumonia from bronchiolitis and interstitial pneumonias, which are less serious.

“The majority of patients with primary influenza pneumonia require ventilatory support,” Rello and Pop-Vicas added. The lung infection interferes with oxygen uptake and may cause low oxygen levels in the blood. Patients who progress to acute respiratory distress syndrome are hospitalized and treated with a breathing tube and mechanical ventilation.

Other viruses can cause viral pneumonia as well. Dr. Luiz Tadeu Moraes Figueiredo of the University of Sao Paulo, Brazil, reported that 1,200 viruses are known to infect the respiratory tract. Not all cause disease. However, several common viruses can cause pneumonia even in immunocompetent individuals:

1. Influenza A and B
2. Parainfluenza
3. Respiratory syncytial virus (RSV)
4. Adenoviruses

In immunocompromised individuals, rhinovirus, coronavirus, hantavirus, and metapneumovirus can cause pneumonia opportunistically.

Treatment for viral pneumonia depends on the type of virus. Oseltamivir and zanamivir are effective against influenza, while ribavirin is effective against RSV, parainfluenza, and adenovirus.


1. PubMed Health. Pneumonia. Web. August 23, 2011.

2. Rello J et al, “Clinical review: Primary influenza viral pneumonia”, Critical Care 2009; 13: 235. http://www.ncbi.nlm.nih.gov/pubmed/20085663

3. Figueiredo LTM, “Viral pneumonia: Epidemiological, clinical, pathophysiological and therapeutic aspects”, J Bras Pneumol. 2009; 35(9): 899-906. http://www.ncbi.nlm.nih.gov/pubmed/19820817

Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.

Reviewed August 30, 2011
by Michele Blacksberg R.N.
Edited by Jody Smith

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