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CMV infections affect more than just patients with compromised immune systems, researchers find

July 25, 2008

An infection due to a virus called cytomegalovirus (CMV), which most commonly affects people with compromised immune systems, can also affect hospital intensive-care patients who have no immune-system problems, University of Washington researchers have found. CMV infection is also associated with longer hospital and intensive-care unit (ICU) stays independent of other causes, according to the study, published July 23 in JAMA, the Journal of the American Medical Association.

About half of all healthy adults in the United States are exposed to CMV during their life, researchers estimate, and control the infection with their immune system, often without even experiencing symptoms. In some people with reduced immune function, such as organ-transplant recipients, the virus can re-activate in the body and cause serious health problems.

In this study, researchers looked at CMV reactivation in 120 patients with no immune-system problems who were admitted to a hospital ICU. They also analyzed how CMV reactivation affected a patient's long-term health outcomes, including the amount of time the patient had to spend in the hospital or ICU and their risk of death.

The researchers found that CMV reactivation was surprisingly common in ICU patients, with about 30 percent exhibiting an active CMV infection in their bloodstream at various points during the 30-day study period. Even when controlling for other possible variables, CMV reactivation was strongly associated with a longer hospital and ICU stay for patients.

"Other studies have looked at the reactivation rate of CMV, but what makes this study different is that we're looking at people with apparently normal immune systems who were being treated in the ICU for trauma or another medical problem," explained Dr. Ajit Limaye, associate professor of medicine and laboratory medicine at the UW, who led the study. "A substantial number of these patients had CMV reactivate in their bloodstream. What's interesting is that having the virus reactivate was associated with longer ICU and hospital stays, independent of other potential variables."

Longer hospital stays can drive up health-care costs, and can be inconvenient or uncomfortable for patients, Limaye added.

Patients without immune system problems are not typically tested for CMV. However, despite the study findings, Limaye said, it would be premature to start routine testing of ICU patients for reactivation of the virus.

First, the researchers will need to see whether using anti-viral drugs to treat regular-immunity ICU patients can help cut down on reactivation of CMV, or whether it can cut down on the length of hospital stays for those patients with the reactivated virus.

"There are side effects associated with the treatment for CMV, and CMV might simply be a marker, rather than a cause," Limaye explained. "Because of that, we need to test the theory that by treating CMV we can improve the endpoint -- the length of stay in the hospital."

If the planned clinical trial shows that treatment can cut down on CMV reactivation and reduce hospital stays for those patients, Limaye said, it could bring about a new paradigm for improving outcomes for hospital ICU patients. ICUs are typically focused on pulmonary and critical care, he explained, but CMV is an infectious-disease issue.

University of Washington