Incidence of influenza virus infections confirmed by serology in children and adult in a suburb community, northern China, 2018‐2019 influenza season

Abstract

Background In mainland China, seasonal influenza disease burden at community level is unknown. The incidence rate of influenza virus infections in the community is difficult to determine due to the lack of well‐defined catchment populations of influenza‐like illness surveillance sentinel hospitals. Objectives We established a community‐based cohort to estimate incidence of seasonal influenza infections indicated by serology and protection conferred by antibody titers against influenza infections during 2018‐2019 influenza season in northern China. Methods We recruited participants in November 2018 and conducted follow‐up in May 2019 with collection of sera every survey. Seasonal influenza infections were indicated by a 4‐fold or greater increase of hemagglutination inhibition (HI) antibody between paired sera. Results Two hundred and three children 5‐17 years of age and 413 adults 18‐59 years of age were followed up and provided paired sera. The overall incidence of seasonal influenza infection and incidence of A(H3N2) infection in children (31% and 17%, respectively) were significantly higher than those in adults (21% and 10%, respectively). The incidences of A(H1N1)pdm09 infection in children and adults were both about 10%, while the incidences of B/Victoria and/Yamagata infection in children and adults were from 2% to 4%. HI titers of 1:40 against A(H1N1)pdm09 and A(H3N2) viruses were associated with 63% and 75% protection against infections with the two subtypes, respectively. Conclusions In the community, we identified considerable incidence of seasonal influenza infections. A HI titer of 1:40 could be sufficient to provide 50% protection against influenza A virus infections indicated by serology.

Incidence of medically attended influenza and influenza virus infections confirmed by serology in Ningbo City from 2017–2018 to 2019–2020

“…Noticeably, our study has identified not only substantial outpatient burden (range: 2.7–19.8%) in people aged ≥60 years but also high risks of infections with influenza indicated by serology in the age group. Although the wintertime influenza season in 2019–2020 ended earlier, the incidence rate of infection with influenza virus indicated by serology in people aged ≥60 years reached 25% (95% CI: 21–30%), which was slightly higher than that (21%; 95% CI: 17–25%) in adults 18–59 years in another serological cohort study conducted in Shanxi Province in 2018–2019 20 . Contrary to other studies in other countries and China, our study indicated that the influenza‐associated outpatient burden in people aged ≥60 years was higher than those in adults under 60 years 8,15–18 .…”

The Antibody Response Against Neuraminidase in Human Influenza A (H3N2) Virus Infections During 2018/2019 Flu Season: Focusing on the Epitopes of 329-N-Glycosylation and E344 in N2

“…The cohort, including 203 children 5–17 years old and 413 adults 18–59 years old, was enrolled in the pre– and post–flu season of 2018/2019. The overall infection incidence based on serological tests was reported in our previous work ( Xu et al, 2021 ). The research protocol was approved by the institutional review board of the National Institute for Viral Disease Control and Prevention, Chinese Centers for Disease Control and Prevention, and written informed consent was obtained from the participants.…”

“…The global head of HA is highly variant, and NA is relatively conserved. For HI, the assay is conventionally used to characterize antigenicity, diagnosis, or vaccine evaluation ( Schulman and Kilbourne, 1969 ; Eichelberger and Wan, 2015 ; Xu et al, 2021 ), while it is limited in the current seasonal H3N2 virus experiments. Anti-NA Abs could alleviate clinical severity by inhibiting viral release from infected cells ( Schulman, 1969 ; Couch et al, 2013 ; Eichelberger and Wan, 2015 ).…”

“…During the 2018/2019 flu season, we collected the paired sera from 203 children 5–17 years old and 413 adults aged 18–59 years in Northern China ( Xu et al, 2021 ). The current work aimed to explore the anti-N2 responses in the individuals who showed seroconversion of MN Ab titers to the circulating H3N2 strains, indicating being naturally infected.…”

COVID-19 and School: To Open or Not to Open, That Is the Question. The First Review on Current Knowledge

“…A three-year prospective study carried out in Hong Kong estimated that the cumulative infection incidence in the subjects enrolled (aged between 5 and 17) was 59% during the first wave of H1N1 in 2009, then 7%, 14%, 20%, and 31% during the subsequent epidemics of H3N2 (2010), H1N1pdm09 (2011), B (2012) and H3N2 (2012), respectively [ 5 ]. Following the same approach, a study on the varying incidence of the influenza virus among children (203 subjects enrolled, aged between 5 and 17) and adults (413 subjects enrolled, aged between 18 and 59), based on antibody testing, showed an overall incidence rate of seasonal influenza of 31% and 21% in the two groups [ 90 ]. Several prototypes have been designed to describe how school closure might lead to a reduction in the incidence peak of the influenza virus pandemic; an example of this is the study by Ferguson et al [ 91 ], pointing to a drop by as much as 40%.…”