Influenza coinfections often overlooked

Doctors who diagnose patients with bacterial infections during flu season should consider the possibility of influenza coinfection, according to a study published in The Journal of Infectious Diseases.

“Only a fraction of all persons with influenza are clinically diagnosed with influenza,” Katherine A. Poehling, MD, MPH, of the department of pediatrics, Wake Forest School of Medicine, and colleagues wrote. “Clinical symptoms of influenza often overlap with symptoms associated with other respiratory viruses as well as symptoms associated with other illnesses.”

Other factors for not properly diagnosing influenza include the variable timing and duration of influenza seasons and the limited specificity of rapid influenza diagnostic tests, according to Poehling and colleagues. Lack of diagnosis can adversely affect treatment, particularly for those who are hospitalized or with high-risk conditions.

The researchers conducted prospective influenza surveillance of emergency and inpatient settings in three North Carolina hospitals during four consecutive flu seasons from 2009 to 2013. Study enrollment included 4,689 men, women and children within 24 to 48 hours of presentation, Poehling and colleagues wrote. More than 70% of these patients had cough, nasal congestion and fever, while fatigue/malaise was reported for most adults.

Eleven percent were found to have laboratory-confirmed influenza, according to the researchers. Of these, 29% (95% CI, 25%-33%) received a clinical diagnosis of influenza. The number increased to 56% (95% CI, 50%-63%) for those with laboratory-confirmed influenza and high-risk conditions, which included chronic or pulmonary diseases, diabetes, cancer, HIV and more.

Nearly one-third of patients with laboratory-confirmed influenza were diagnosed for bacterial infection and were prescribed antibiotics. Only 18% of patients with a bacterial diagnosis who were using antibiotics and with confirmed influenza were diagnosed with influenza.

“We found that the odds of an influenza diagnosis were over threefold lower for all patients with a bacterial diagnosis, including those with high-risk conditions,” Poehling and colleagues wrote. “Thus, during the influenza season, clinicians should consider if persons with symptoms consistent with a bacterial infection could also have influenza and if coinfection with influenza would alter the treatment recommendations.” – by David Jwanier

Disclosures: Miller reports no relevant financial disclosures. Poehling and another author have received research support from BD Diagnostics and MedImmune.