By David Douglas

NEW YORK (Reuters Health) - Human metapneumovirus, which was first identified in 2001 in children, is among the respiratory viruses that affect adults of all ages, New York-based researchers have found.

The study, Dr. Edward E. Walsh told Reuters Health, "demonstrates that repeat infections with childhood viruses are common in all adults, and along with respiratory syncytial virus (RSV) and influenza virus cause a significant disease burden in older adults, especially among those hospitalized during the winter months with respiratory illness."

Walsh of Rochester General Hospital and colleagues came to this conclusion after studying 291 young people (ages 19 to 40 years), 611 healthy elderly people (ages 65 or more), 537 high-risk elderly, and a hospitalized cohort of 1386 patients. They were followed over the winters of 1999 through 2003.

The incidence of metapneumovirus infection ranged from 2.2 percent to 10.5 percent in the healthy outpatient cohorts. Infections were symptom-less in at least 38.8 percent of each of these cases. Symptoms, when apparent, were typical of upper respiratory tract infections (i.e., wheeze, cough, fever), but some high-risk participants had to be admitted to the hospital for treatment.

In the hospitalized group of patients, the overall incidence of metapneumovirus was 8.5 percent but ranged from 4.4 percent to 13.3 percent depending on the year. Dual infections were seen in 22.9 percent. The most frequent co-infections were with RSV, coronavirus, and influenza A.

The study findings, Walsh concluded, "point out that influenza vaccination cannot be expected to prevent all illnesses that appear to be influenza-like in older persons."

SOURCE: Archives of Internal Medicine, December 2008.

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