The secular trend of enterovirus A71 after the implementation of preventive measures in Taiwan

Abstract

Background: Enterovirus A71 (EV A71) is one of the most important enteroviruses related to morbidity and mortality in children worldwide. This study aimed to analyse the secular trend of EV A71 in Taiwan from 1998 to 2020 and to evaluate the effectiveness of infection control measures.

Methods: We collected the epidemiological data of EV A71 from disease surveillance systems in Taiwan. We analysed the association between the secular trend of EV A71 and preventive measures such as hand washing, case isolation, and suspension of classes.

Results: The incidence of enterovirus infections with severe complications (EVSC) decreased from 16.25 per 100,000 children under six in 1998 to less than 9.73 per 100,000 children under six after 2012 (P = 0.0022). The mortality rate also decreased significantly, from 3.52 per 100,000 children under six in 1998 to 0 per 100,000 children under six in 2020 (P < 0.0001). The numbers of EVSC and fatalities were significantly higher in the years when EV A71 accounted for more than 10% of the annual predominant serotypes (p < 0.05). After the implementation of many non-pharmaceutical interventions in 2012, the incidence of EVSC and mortality rate decreased significantly (p < 0.001).

Conclusions: After implementing active enterovirus surveillance and preventive measures, we found that the incidence of EVSC and fatalities due to EV A71 in Taiwan decreased significantly from 1998 to 2020. Continuous surveillance and strengthened infection control policies are still needed in the future.

Keywords: Complication; Enterovirus A71; Epidemiology; Infection control; Surveillance system.

Fig. 1

The incidence of enterovirus infection with severe complications and mortality in children under six-year-old, 1998–2020. The incidence of enterovirus infection with severe complications (EVSC) and mortality rate decreased significantly from 1998 to 2020. The average annual percentage change (AAPC) for the incidence of EVSC was −9.19% (95%CI −3.40, −14.64, P = 0.0022). The AAPC for mortality in children younger than six years of age was −12.81% (95%CI −7.73, −17.63, P < 0.0001)

Fig. 2

Proportion of weekly emergency visits for hand, foot and mouth disease and herpangina, 2007–2020. The peak proportion of weekly emergency visits for HFMD and herpangina occurred between week 20 and week 40 each year. The number of individuals with herpangina was higher than the number of individuals with HFMD every year. The peak annual proportion of emergency visits for enterovirus infection was less than 10% after 2017

Fig. 3

Number of weekly outpatient and emergency visits for enterovirus infection in Taiwan, 2007–2020. The number of outpatient and emergency visits for enterovirus infection showed a seasonal distribution. The peak occurred between week 20 and week 40 annually. The number of outpatient and emergency visits for enterovirus infection reached the lowest point in 2020

Fig. 4

Number of severe or fatal enterovirus infection and the implementation of surveillance and preventive measures, 1998–2020. The numbers of enterovirus infection with severe complications (EVSC) cases and fatality showed a downward trend within the past 20 years. When EV A71 accounted for more than 10% of the annually predominant serotypes (marked with *), both the annual number of EVSC cases and the annual number of fatalities were significantly higher than those in the years when EV A71 accounted for less than 10%

Fig. 5

Enterovirus virus isolates according to contracted virology laboratories, 2006–2020. The Taiwan CDC integrated viral contract laboratories for enterovirus isolation since March 1999, and data integration was completed in 2006. The number of EV A71 isolates decreased progressively, and few A71 enteroviruses were isolated after 2012. The average annual positive rate of enterovirus detection was 12%. The mean percentage of EV A71 was 9.1% annually