SAN DIEGO -- During the winter of 2006 and the spring of 2007, adenovirus 14 caused a community outbreak of respiratory disease in Oregon, with a fatality rate of 19%, Dr. Paul Lewis reported at the annual meeting of the Infectious Diseases Society of America.

"This seemed to come out of nowhere," Dr. Lewis, a public health physician with the state of Oregon and a pediatric infectious disease physician with Oregon Health and Science University, Portland, said of the outbreak. "In patients with serious respiratory illness without an identified etiology, clinicians should think about viruses."

The cluster was first identified in the spring of 2007 by his associate, Dr. David Gilbert, who was making rounds in the intensive care unit at Providence Portland Medical Center and thought it was odd that 4 of 13 patients had adenovirus infections, which are typically mild and self-limited.

"When we called other hospitals in the Portland area, we almost fell out of our chairs because they all had seen recent severe and fatal cases of adenovirus," Dr. Lewis said.

The researchers studied 45 cases of adenovirus that were detected in Oregon medical laboratories between November 2006 and April 2007. The adenovirus isolates were typed by hexon gene sequencing or by a novel adenovirus 14-specific real-time polymerase chain reaction assay.

More than 75% of all adenovirus cases were in male patients. Of the 45 cases, 31 (69%) were adenovirus 14, a serotype first identified in 1953 but seen infrequently and never in outbreaks since that time.

Patients infected with adenovirus 14 were significantly older than patients infected with other adenovirus isolates (a mean of 59 yearsvs. 1 year, respectively). They also had significantly higher rates of hospitalization (71% vs. 14%, respectively).

Clinical features of patients with adenovirus 14 included fever (84%), tachypnea (77%), hypoxia (48%), and hypotension (43%). Of the 24chest x-rays obtained, 21 (88%) had abnormal findings. Lobar consolidation was the most common pattern seen.

Dr. Lewis reported that 22 (71%) of the adenovirus 14 patients required hospitalization, and 6 (19%) died. Of the hospitalized patients, 16 (73%) required ICU care, 13 (59%) required mechanical ventilation, and 8 (36%) required blood pressure support with vasopressors.

"Infection control was a great concern to hospitals that saw multiple cases," Dr. Lewis said. "Many patients were isolated with [severe acute respiratory syndrome]-like precaution. There was a health care worker at an ICU taking care of one of these patients who was subsequently admitted to that ICU with adenovirus 14," he added. "That's our only known possible case of transmission, but we cannot be sure it was not acquired in the community."

Treatment included "lots of empiric antibiotics." Cidofovir was used in six patients, two of whom died.

Dr. Lewis said that there are 51 known adenovirus serotypes. Types1, 2, and 5 are nearly universal in children, whereas types 3, 4, and 7 are common in adults. No adenovirus vaccine is currently available in the United States, and previous vaccines developed for the military do not cover adenovirus 14.

He acknowledged certain limitations of the study, including its retrospective design and the potential for testing bias.