The prevalence and endemic nature of dengue infections in Guangdong, South China: an epidemiological, serological, and etiological study from 2005-2011

Abstract

Objectives: Frequent outbreaks of dengue are considered to be associated with an increased risk for endemicity of the disease. The occurrence of a large number of indigenous dengue cases in consecutive years indicates the possibility of a changing dengue epidemic pattern in Guangdong, China.

Methods: To have a clear understanding of the current dengue epidemic, a retrospective study of epidemiological profile, serological response, and virological features of dengue infections from 2005-2011 was conducted. Case data were collected from the National Notifiable Infectious Diseases Reporting Network. Serum samples were collected and prepared for serological verification and etiological confirmation. Incidence, temporal and spatial distribution, and the clinical manifestation of dengue infections were analyzed. Pearson's Chi-Square test was used to compare incidences between different age groups. A seroprevalence survey was implemented in local healthy inhabitants to obtain the overall positive rate for the specific immunoglobulin (Ig) G antibody against dengue virus (DENV).

Results: The overall annual incidence rate was 1.87/100000. A significant difference was found in age-specific incidence (Pearson's Chi-Square value 498.008, P<0.001). Children under 5 years of age had the lowest incidence of 0.28/100000. The vast majority of cases presented with a mild manifestation typical to dengue fever. The overall seroprevalence of dengue IgG antibody in local populations was 2.43% (range 0.28%-5.42%). DENV-1 was the predominant serotype in circulation through the years, while all 4 serotypes were identified in indigenous patients from different outbreak localities since 2009.

Conclusions: A gradual change in the epidemic pattern of dengue infection has been observed in recent years in Guangdong. With the endemic nature of dengue infections, the transition from a monotypic to a multitypic circulation of dengue virus in the last several years will have an important bearing on the prevention and control of dengue in the province and in the neighboring districts.

Figure 1. Age-specific incidence of dengue infections in Guangdong, China, 2005–2011.

Incidences were indicated with the line chart. The proportion of age-specific cases to the total number was shown with the bar chart.

Figure 2. Onset month of dengue cases by infection origin in Guangdong, China, 2005–2011.

Imported and indigenous dengue cases were shown with the stacked bar chart using different filling patterns.

Figure 3. Spatial distribution of dengue cases by infection origin in Guangdong, China, 2005–2011.

X-axis represents different prefectures (e.g. GZ,ZH,FS) and areas (PRDA, EA, WA, MA) of Guangdong province: Data tables were shown under the chart to display the case number of imported and indigenous cases. GZ (the metropolis capital city of Guangdong) in PRDA, ST in EA, and ZJ in WA were the top 3 clustered areas.

Figure 4. Clinical presentations of dengue infections in Guangdong, China, 2005–2011.

Percentage of certain clinical symptom was shown with the line chart. Case number was shown with the bar chart. Data labels of percentage were appended to the line chart.

Figure 5. Seroprevalence of specific immunoglobulin (Ig) G antibody against dengue virus among healthy inhabitants.

Data were collected through 2003–2011 in 4 sentinel cities of Guangdong, south China. Seroprevalence rate of IgG antibody by year was shown with the line chart. The average positive rate of IgG antibody was 2.43%.

Figure 6. Serotypes of dengue virus identified in autonomous dengue patients from outbreak localities of Guangdong.

Etiology data were collected from 2001 to 2012 (as of September 15, 2012). No viruses were isolated from indigenous cases in 2003 and 2005. Stacked bar chart was used to show the different serotypes of dengue viruses with different filling patterns.