Two reports of pneumonia associated with ECHO virus type 9, infection in two adult siblings are presented. Other manifestations of this infection consisted of aseptic meningitis in the brother (J. P.) and hepatitis in his sister (C. P.).
These patients were afflicted consecutively with febrile illnesses, and ECHO 9 virus was isolated from the pharyngeal secretions of both patients. A significant increase of the homologous neutralizing antibody was demonstrated in the serum of the second patient (C. P.), although not in her brother (J. P.), possibly because the acute phase serum was obtained too late in his illness.
The need to consider enteroviruses as being associated with pneumonia, even in adults, is emphasized, and, like the group B, Coxsackie viruses, ECHO 9 viral pneumonia may be associated with pleurisy and pleurodynia in adults.
The clinical features of the second case (Patient C. P.) would suggest that patients with an enterovirus infection should be investigated for associated liver involvement. Conversely, it appears that some patients with hepatitis might be found to have an associated specific enterovirus infection simultaneously, which should be investigated, particularly when other organ systems appear to be involved at the same time. At any rate, ECHO 9 virus should be listed as another of the so-called "candidate viruses" that can be associated with hepatocellular damage and liver function abnormalities, even in adults. Further study and clarification is needed to determine whether these "candidate viruses" have a true causal role in some forms of hepatitis.