The changing epidemiology of dengue in China, 1990-2014: a descriptive analysis of 25 years of nationwide surveillance data

Abstract

Background: Dengue has been a notifiable disease in China since 1 September 1989. Cases have been reported each year during the past 25 years of dramatic socio-economic changes in China, and reached a historical high in 2014. This study describes the changing epidemiology of dengue in China during this period, to identify high-risk areas and seasons and to inform dengue prevention and control activities.

Methods: We describe the incidence and distribution of dengue in mainland China using notifiable surveillance data from 1990-2014, which includes classification of imported and indigenous cases from 2005-2014.

Results: From 1990-2014, 69,321 cases of dengue including 11 deaths were reported in mainland China, equating to 2.2 cases per one million residents. The highest number was recorded in 2014 (47,056 cases). The number of provinces affected has increased, from a median of three provinces per year (range: 1 to 5 provinces) during 1990-2000 to a median of 14.5 provinces per year (range: 5 to 26 provinces) during 2001-2014. During 2005-2014, imported cases were reported almost every month and 28 provinces (90.3%) were affected. However, 99.8% of indigenous cases occurred between July and November. The regions reporting indigenous cases have expanded from the coastal provinces of southern China and provinces adjacent to Southeast Asia to the central part of China. Dengue virus serotypes 1, 2, 3, and 4 were all detected from 2009-2014.

Conclusions: In China, the area affected by dengue has expanded since 2000 and the incidence has increased steadily since 2012, for both imported and indigenous dengue. Surveillance and control strategies should be adjusted to account for these changes, and further research should explore the drivers of these trends.

Figure 1

The incidence of dengue cases reported in mainland China, 1990-2014 (N = 69,321). Panel A: The aggregated number of cases by year with the numbers of deaths in parentheses. Panel B: The morbidity of dengue per one million residents of mainland China at the end of each year.

Figure 2

The morbidity of imported (N = 2,061) and indigenous (N = 53,053) dengue cases by month per one million residents of affected provinces at the end of each year in mainland China, 2005-2014.

Figure 3

The age and gender distribution and proportion of imported (N = 2,061) and indigenous (N = 53,053) dengue cases that were laboratory confirmed by year, 2005-2014. Panel A: The age distribution of male and female imported cases. Panel B: The age distribution of male and female indigenous cases. Panel C: The proportion of imported cases that were laboratory confirmed each year. Panel D: The proportion of indigenous cases that were laboratory confirmed each year.

Figure 4

Heat map of dengue surveillance data by Chinese province, sorted by latitude of capital city, 1990-2014 (N = 69,321). On the Y-axis is listed the name of the province with the latitude of the capital city and a general classification of climate zone for each province. M: Mid-temperate; W: warm-temperate; C: cold; S: subtropical; T: tropical. A thumbnail map of all the provinces of China is provided at the end of the figure. Panel A: Time series of monthly dengue cases, 1990-2014, standardized by the number of total cases reported by each province. Panel B: Time series of monthly imported dengue cases, 2005-2014, standardized by the number of total cases reported by each province. Panel C: Time series of monthly indigenous dengue cases, 2005-2014, standardized by the number of total cases reported by each province. Panel D: Seasonal distribution of imported dengue cases, plotted as the mean value of the proportion of cases in each week of the year from 2005 to 2014. Panel E: Seasonal distribution of indigenous dengue cases, plotted as the mean value of the proportion of cases in each week of the year from 2005 to 2014.

Figure 5

Years in which the first case of dengue was reported in each province in the time period of our dataset, 1990-2014.

Figure 6

The geographic distribution of dengue cases in mainland China, 2013 and 2014. Panel A: The distribution of dengue cases in 2013 (N = 4,779). Panel B: The distribution of dengue cases in 2014 (N = 47,056).