Viral infections are common among critically ill patients, difficult to diagnose and therefore under-reported and under-recognized as pathogens. Fourteen posters presented May 17 shed light on the influence of emerging and novel viruses on illnesses and clinical outcomes for patients.

In C59 “H1N1 Influenza and Other Viral Infections: Clinical Manifestations, Diagnosis and Outcomes,” co-moderator Robert Fowler, MDCM, MS, FRCPC, associate professor of medicine and critical care medicine at Sunnybrook Hospital at the University of Toronto, described how these studies highlight the difficulties in diagnosis, mechanisms to improve sensitivity in finding viruses and novel therapies that deserve further attention and study.

Many of the posters focused on H1N1. Data from Buenos Aires suggests that the 2009 infection rate was as high as 29 percent. The majority of seropositive individuals were younger—predominately children and school-age adolescents.

Other groups found that positive bacterial cultures are common in patients critically ill with H1N1 and that most of those bacterial infections are acquired in ICUs. Researchers from around the world noted high rates of co-infection with H1N1.

In Japan, Streptococcus pneumoniae was found in 34 percent of H1N1 patients suspected of having bacterial co-infections. The majority of H1N1 patients are treated with antibiotics during ICU stays, and nosocomial bacterial infections may be associated with worse clinical outcomes. In France, transplant patients were particularly affected by H1N1 and persistent graft functional impairment in lung transplant recipients was discovered.

Both French and U.S. groups found that for patients on ventilator therapy, nasopharyngeal swabs for real-time polymerase chain reaction (PCR) may be inadequate to diagnosis H1N1 within a few days of onset. Viral replication appears to move into the lower respiratory track soon after infection. Researchers recommended use of broncho-alvelor lavage to obtain specimens for real-time PCR in patients suspected of H1N1 infection with pneumonia or acute respiratory distress syndrome when nasopharyngeal PCR is negative.

A triple combination antiviral regimen using oseltamivir, ribavirin and amantadine showed improved outcomes compared to oseltamivir alone in a Korean trial. Researchers concluded that the triple regimen needs confirmation in prospective trials.

In non-H1N1 trials, French researchers found that adults hospitalized with measles have frequent and severe complications with bronchiolitis, thrombocytopenia and hepatitis. The severity of the potential complications reinforces the need for appropriate vaccination.

“Viruses are an under-recognized important cause of illness for patients,” Dr. Fowler said. “We need better ways to diagnose and treat viral infections.”