The presence of fever in adults with influenza and other viral respiratory infections

We compared the rates of fever in adult subjects with laboratory-confirmed influenza and other respiratory viruses and examined the factors that predict fever in adults. Symptom data on 158 healthcare workers (HCWs) with a laboratory-confirmed respiratory virus infection were collected using standardized data collection forms from three separate studies. Overall, the rate of fever in confirmed viral respiratory infections in adult HCWs was 23<bold></bold>4% (37/158). Rates varied by virus: human rhinovirus (25<bold></bold>3%, 19/75), influenza A virus (30%, 3/10), coronavirus (28<bold></bold>6%, 2/7), human metapneumovirus (28<bold></bold>6%, 2/7), respiratory syncytial virus (14<bold></bold>3%, 4/28) and parainfluenza virus (8<bold></bold>3%, 1/12). Smoking [relative risk (RR) 4<bold></bold>65, 95% confidence interval (CI) 1<bold></bold>33-16<bold></bold>25] and co-infection with two or more viruses (RR 4<bold></bold>19, 95% CI 1<bold></bold>21-14<bold></bold>52) were significant predictors of fever. Fever is less common in adults with confirmed viral respiratory infections, including influenza, than described in children. More than 75% of adults with a viral respiratory infection do not have fever, which is an important finding for clinical triage of adult patients with respiratory infections. The accepted definition of influenza-like illness' includes fever and may be insensitive for surveillance when high case-finding is required. A more sensitive case definition could be used to identify adult cases, particularly in event of an emerging viral infection.