Viral and bacterial upper respiratory tract infection in hospital health care workers over time and association with symptoms

Raina MacIntyre, C.; Chughtai, Abrar Ahmad; Zhang, Yi; Seale, Holly; Yang, Peng; Chen, Joshua; Pan, Yang; Zhang, Daitao; Wang, Quanyi

Of interest, we identified 5 cases of asymptomatic viral infection -four rhinovirus/enterovirus and one influenza A(H3N2). Few studies have been conducted on the incidence of asymptomatic viral infection, and of these, the results are often inconsistent. One study examined the rate of asymptomatic infection resulting from inoculation and found that 1/3 of participants did not develop any symptoms [23] whereas a more recent study found the rate of respiratory illness attributable to influenza infection to be 27 respiratory illnesses per 100 persons [29] . Our findings indicated a high rate of asymptomatic infection at baseline, being cleared without the development of symptoms. The clinical significance of such findings is still unknown with limited information on viral shedding and transmission in asymptomatic subjects. It is well known that influenza virus is shed from the respiratory tract in the incubation period in asymptomatic subjects, and asymptomatic infection has also been observed with parainfluenza virus infection [22] . It has also been found that viral shedding of influenza occurs on average for 5 days after infection, indicating that some positive tests could have been in HCWs recovering from influenza [22] . Asymptomatic viral infections pose a significant risk of nosocomial transmission to both patients and HCWs.