FRIDAY, April 19, 2019 (HealthDay News) -- Many hospital workers and patients spread the flu before they show any symptoms, a new study says.
The bottom line: Current flu infection control measures in hospitals may be inadequate, the Swiss researchers say.
"Our findings suggest that influenza infection in acute care is common and a significant proportion of individuals appear to shed influenza virus without harboring any symptoms, making the spread of flu very difficult to control even with self-diagnoses and current infection control practices," said study author Dr. Stefan Kuster, of University Hospital of Zurich and the University of Zurich.
Over two consecutive flu seasons (2015-2016 and 2016-2017), the researchers followed 152 health care workers and 542 admitted patients at University Hospital. Flu tests were conducted daily.
During those flu seasons, 11% of the health care workers and 4% of the patients were diagnosed with a flu infection. Most developed flu symptoms, but two of the staff and two of the patients had no flu symptoms.
The researchers also found that 17% of 71 flu-positive swabs collected from health care workers and 8% of 38 flu-positive swabs from patients were obtained on days when they had no flu symptoms.
Moreover, among 14 health care workers infected with the flu, two had a positive flu test before symptoms developed.
The study was presented April 13-16 at the European Congress of Clinical Microbiology & Infectious Diseases, in Amsterdam.
"Influenza vaccination is not perfect but remains the best tool we have to protect health care workers and their patients from severe illness," Kuster said in a news release from the congress.
Data and conclusions presented at meetings are usually considered preliminary until published in a peer-reviewed medical journal.
The U.S. Centers for Disease Control and Prevention has more on flu prevention.