Relative transmissibility of shigellosis among different age groups: A modeling study in Hubei Province, China

Abstract

Shigellosis is a heavy disease burden in China especially in children aged under 5 years. However, the age-related factors involved in transmission of shigellosis are unclear. An age-specific Susceptible–Exposed–Infectious/Asymptomatic–Recovered (SEIAR) model was applied to shigellosis surveillance data maintained by Hubei Province Centers for Disease Control and Prevention from 2005 to 2017. The individuals were divided into four age groups (≤ 5 years, 6–24 years, 25–59 years, and ≥ 60 years). The effective reproduction number (Reff), including infectivity (RI) and susceptibility (RS) was calculated to assess the transmissibility of different age groups. From 2005 to 2017, 130,768 shigellosis cases were reported in Hubei Province. The SEIAR model fitted well with the reported data (P < 0.001). The highest transmissibility (Reff) was from ≤ 5 years to the 25–59 years (mean: 0.76, 95% confidence interval [CI]: 0.34–1.17), followed by from the 6–24 years to the 25–59 years (mean: 0.69, 95% CI: 0.35–1.02), from the ≥ 60 years to the 25–59 years (mean: 0.58, 95% CI: 0.29–0.86), and from the 25–59 years to 25–59 years (mean: 0.50, 95% CI: 0.21–0.78). The highest infectivity was in ≤ 5 years (RI = 1.71), and was most commonly transmitted to the 25–59 years (45.11%). The highest susceptibility was in the 25–59 years (RS = 2.51), and their most common source was the ≤ 5 years (30.15%). Furthermore, “knock out” simulation predicted the greatest reduction in the number of cases occurred by when cutting off transmission routes among ≤ 5 years and from 25–59 years to ≤ 5 years. Transmission in ≤ 5 years occurred mainly within the group, but infections were most commonly introduced by individuals in the 25–59 years. Infectivity was highest in the ≤ 5 years and susceptibility was highest in the 25–59 years. Interventions to stop transmission should be directed at these age groups.

Computing R0 of dynamic models by a definition-based method

“…Some studies adopted calculated R 0 to estimate the transmissibility of infectious diseases, such as shigellosis (Z. Zhao, Chen, et al., 2021 ), HFMD ( Xu et al., 2021 ), and COVID-19 ( Zhao et al, 2021a ). However, the detailed steps of deriving the R 0 expression are not illustrated.…”

Theoretical Epidemiology Needs Urgent Attention in China

“…These models often rely heavily on data, overlooking the infectious and epidemiologic aspects of disease (34). Typically, such models focus solely on prediction, utilizing historical data to simulate scenarios for forecasting, and rarely assess the effectiveness of infectious disease prevention and control strategies (35)(36).…”

“…These models simulate population dynamics, progressing from susceptibility to incubation, symptomatic or asymptomatic infection, and eventual recovery or mortality. They incorporate key epidemiological factors such as infectiousness, pathogenicity, and virulence ( 1 , 6 , 37 – 39 ). Additionally, they integrate practical prevention and control measures, including pharmacological interventions (e.g., antiviral drugs, antibiotics, vaccines) and non-pharmacological strategies (such as contact tracing, testing, school closures, hand hygiene, social distancing, mask-wearing), environmental disinfection, and vector control.…”

Vaccination with a Protective Ipa Protein-Containing Nanoemulsion Differentially Alters the Transcriptomic Profiles of Young and Elderly Mice following Shigella Infection

“…While shigellosis affects individuals of all age groups and is an important cause of morbidity and mortality in children under the age of five [14,15], we focus here on understanding its impact on both young and elderly populations [16]. The elderly, often defined as individuals aged 65 years and older, are known to experience an increased susceptibility to infectious diseases due to age-related changes in their immune system and underlying health conditions [17].…”