Incidence, symptoms and medical care for influenza virus and respiratory syncytial virus illnesses among older adults in Eastern China: Findings from the China Ageing Respiratory Infections Study (CARES), 2015-2017

IntroductionFew studies have examined the incidence of virologic-confirmed influenza virus and respiratory syncytial virus (RSV) infections in community-dwelling older adults. MethodsWe enrolled adults aged 60-89 years in Jiangsu Province, China and followed them weekly from December 2015-September 2017 to identify acute respiratory illnesses (ARI), collect illness information and respiratory specimens for laboratory testing. Results1,527 adults were enrolled, 0{middle dot}4% reported ever receiving influenza vaccination. 95 PCR-confirmed influenza ARIs and 22 RSV ARIs were identified, among whom 4-5% required hospitalization. One death associated with RSV ARI while none for influenza ARIs was observed. From December 2015-August 2016, the cumulative incidences of influenza and RSV ARIs were 0{middle dot}8% (95% CI:0{middle dot}3-1{middle dot}4) and 0{middle dot}5% (95% CI:0{middle dot}1-1{middle dot}0), respectively. From September 2016-August 2017, the cumulative incidences were 6{middle dot}1% (95% CI:4{middle dot}7-7{middle dot}7) and 1{middle dot}0% (95% CI:0{middle dot}5-1{middle dot}6); the influenza and RSV ARI-associated hospitalization incidences were 0{middle dot}3% (95% CI:0-0{middle dot}8) and 0{middle dot}1% (95% CI:0-0{middle dot}2). Feverishness was more common in influenza (55%) than RSV ARIs (30%, p=0{middle dot}03). Influenza (12{middle dot}5 days, p=0{middle dot}02) and RSV ARI symptoms (14{middle dot}1 days, p=0{middle dot}15) lasted longer compared to PCR-negative/other ARIs (11{middle dot}0 days). Antibiotic use was more common for influenza (65%, p=0{middle dot}02) and RSV (70%, p=0{middle dot}04) ARIs than other ARIs (51%). ConclusionsWe observed a higher incidence of influenza relative to RSV infections among community-dwelling older adults compared to prior studies. Our findings suggest older adults may benefit from receiving influenza and RSV vaccines to reduce the occurrence of illnesses.