Studies of influenza virus infection in newborn ferrets.

Influenza virus infection by the intranasal route was found to be invariably fatal in newborn ferrets. Some obviously died of influenza pneumonia; others died of aspiration pneumonia or showed only minimal or non-specific changes in the lungs. All, however, had severe lesions in the upper respiratory tract, and it is suggested that obstruction of airways and oesophageal passages, in combination with feeding difficulties, played a major role in causing death. The relevance of the findings to the pathology of cot deaths in human infants is briefly discussed.