Defining RSV epidemic season in southwest China and assessing the relationship between birth month and RSV infection: A 10‐year retrospective study from June 2009 to May 2019

Abstract

Respiratory syncytial virus (RSV) is one of the most common causes of lower respiratory tract infections (LRTI). However, only limited information is available regarding its seasonality and its relationship with birth month. A retrospective hospital‐based study was carried out from June 2009 to May 2019 in Chongqing, southwest of China. LRTI cases under 5 years were enrolled in this study and PCR was used to detect 8 respiratory viruses. RSV seasonality was determined using “average annual percentage” (AAP) and “percent positivity” method. A total of 6991 cases were enrolled in this study, with an RSV positivity of 34.5%. From June 2009 to May 2019, we analyzed RSV epidemic season during 10 RSV epidemic years in Chongqing using two methods. The result of AAP method was similar to that of percent positivity method with a 30% threshold, which showed an epidemic season of roughly October to March in the subsequent year, with a small peak in June. On average, the RSV epidemic season in RSV‐A dominant years typically started earlier (week 42 for RSV‐A vs. week 46 for RSV‐B), ended earlier (week 12 for RSV‐A vs. week 14 for RSV‐B), lasted longer (24 weeks for RSV‐A vs. 22 weeks for RSV‐B), and reached its peak earlier (week 2 for RSV‐A vs. week 3 for RSV‐B) than in RSV‐B dominant years. The proportion of severe LRTI was higher in cases of single infection with RSV‐A compared to those of single infection with RSV‐B (26.3% vs. 22.3%, p = 0.024). Among infants under 1 year, those born in May and August through December were more likely to be infected with RSV. Infants born 1–2 months before the epidemic season were relatively more susceptible to RSV infection. In Chongqing, the RSV epidemic was seasonal and usually lasted from October to March of next year with a small peak in summer. Infants born 1–2 months before the epidemic season were relatively more susceptible to RSV infection and this population should be targeted while developing RSV immunization strategies.

Respiratory syncytial virus incidence and typing in the last six seasons in the north of Spain (Asturias). Genetic characterization during the SARS‐CoV‐2 pandemic

“…Reinfections occur commonly, including in older adults 18 . RSV‐associated in‐hospital mortality increases exponentially with age, posing a greater risk for older adults, particularly frail and high‐risk patients 8,9,19,20 . Moreover, RSV infection may result in greater morbidity and mortality among older hospitalized adults than influenza 21 .…”

“…RSV is considered as a major cause of lower respiratory tract infections among young children, elderly and immunocompromised adults worldwide, 2–5 and is a frequent cause of hospitalization 6,7 . In a recent systematic analysis, it was associated with 6.6 million acute lower respiratory infections, where more than 1 million were hospitalized and 10 000 dead in the hospital 8 . For example, in the United States, RSV infections cause between 58 000 and 80 000 hospitalizations each year in children under 5 years of age and between 60 000 and 160 000 in adults over 65 years of age 9 …”

Respiratory Syncytial Virus incidence and typing in the last 6 seasons in the north of Spain (Asturias). Genetic characterization during the SARS-Cov-2 pandemic

“…Types RSV-A and RSV-B are simultaneously present in most outbreaks, but RSV-A is associated with severe disease. In RSV-A dominant years typically started, reached its peak and lasted than in RSV-B dominant years 8,25 . Several distinct genotypes within these types predominate within a community; the dominant strains shift yearly, perhaps accounting for frequent reinfections 25,26 .…”

“…In recent years, the importance and severity of RSV infections in children as well as adults has been demonstrated and appreciated [1][2][3][4][5][6][7] . RSV-associated in-hospital mortality increases exponentially with age, posing a greater risk for older adults, particularly frail and high-risk patients 8,9,17,18 .Moreover, RSV infection may result in greater morbidity and mortality among older hospitalized adults than influenza 19 . RSV can also causes substantial outpatient illness with lower respiratory tract involvement.…”

“…RSV is considered as a major cause of lower respiratory tract infections amongst young children, elderly and immunocompromised adults worldwide [2][3][4][5] , and is a frequent cause of hospitalization 6,7 . In a recent systematic analysis, it was associated to 6.6 million of acute lower respiratory infection, where more than 1 million were hospitalized and 10000 dead in the hospital 8 . For example, in the United States, RSV infections cause between 58,000 and 80,000 hospitalizations each year in children under 5 years of age and between 60,000 and 160,000 in adults over 65 years of age 9 .…”