Childhood Viruses Pose Lifelong Burden

With No Vaccine, Re-infection Places Many Adults at Risk

June 21, 2001

Respiratory syncytial virus (RSV), and parainfluenza virus - the chief causes of hospitalization for respiratory illness in young children - may be even more menacing than previously believed.

What experts hadn't focused on until now is the consequences of both viruses re-infecting people constantly throughout life, afflicting otherwise healthy teens and adults. In addition, for people whose immune systems are weak, or for the elderly, the re-emergence of these infections can be deadly, reports Caroline B. Hall, M.D., professor of Pediatric Medicine and Infectious Diseases at Strong Memorial Hospital, in a review article published in today's edition of The New England Journal of Medicine.

"These viruses have always been thought of as children's viruses, but we now recognize they may also cause a significant health care burden in older age groups," Hall said. "Unfortunately, the viruses are infrequently recognized by physicians. For instance, someone with heart disease may come to the doctor with an exacerbation of cardiac symptoms, which may actually be the result of an infection with one of these viruses."

Re-infection can spread rapidly from healthy adults to persons at higher risk. For example, Hall reports that among patients in hospitals and long-term care facilities, RSV results in the worsening of chronic lung disease in 5 to 50 percent of cases, and may contribute to death 20 percent of the time.

The scope of infection in young people is staggering: Nearly all children are infected with RSV by the age of 2 years, and re-infection is common thereafter. In families with young children, over 40 percent of adults will acquire the viral infections, Hall said.

The first step to better manage the viruses as they march through all age groups is adequate diagnosis. Hall's goal is to raise awareness: "We can't even judge the health-care burden caused by these viruses without some estimate of the infection rate in older children and adults. And this requires recognizing it as a possible diagnosis. It can be devastating to elderly people in nursing homes, and can also be a big problem for hospital employees who lose a lot of time at work after they are exposed."

Symptoms from RSV or parainfluenza infections can be difficult to sort out in adults because they are similar to the common cold, although they are more severe and last longer. Wheezing and bronchitis are often complications of RSV. The viruses are highly contagious, entering the nose or eyes by hands and by direct contact with large droplets from coughs or sneezes. With an incubation period of two to eight days, outbreaks occur annually from November to May.

Despite four decades of research, there is still no effective means to control RSV or parainfluenza. For babies, a vaccine must be able to offer more protection than the body's natural defenses, and be administered in the first weeks of life. A different type of vaccine could be developed to control re-infection in adults. Those complexities have been the main obstacles to developing a vaccine so far. However, coming up with an RSV vaccine is a national priority, Hall noted.

The only current therapy for RSV infection is an antiviral aerosol approved for use in hospitalized infants. Prevention by giving RSV antibodies that boost the immune system to high-risk, premature infants has also recently been approved. Clinical trials are underway to evaluate whether both treatments work to prevent viral disease in people with severely compromised immune systems.

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