Pneumonia is the most common complication of influenza and may
occur as primary influenza viral pneumonia, secondary bacterial
pneumonia, or a combination. Primary influenza pneumonia is the
most severe of the pneumonic complicators and tends to occur in
patients with underlying cardiac or pulmonary disease. It begins as
typical influenza with fever myalgia and headache and within twelve
to thirty six hours hypoxemia can develop. Sputum production is
scant. Chest x-ray reveals diffuse interstitial infiltrates. Therapy is
mainly supportive as anti-virals have been shown effective mainly
in uncomplicated infections.