Clinical and epidemiological features of the 2014 large-scale dengue outbreak in Guangzhou city, China

Lin et al. BMC Infectious Diseases Clinical and epidemiological features of the 2014 large-scale dengue outbreak in Guangzhou city, China Yong Ping Lin 0 1 4 Yasha Luo 0 3 5 Yuan Chen 0 1 Mart Matthias Lamers 2 Qiang Zhou 3 Xiao Han Yang 3 Sumana Sanyal 2 Chris Ka Pun Mok 2 Zhong Min Liu 1 0 Equal contributors 1 Department of Laboratory Medicine, The First Affiliated Hospital of Guangzhou Medical University , Guangdong , China 2 HKU-Pasteur Research Pole, School of Public Health, HKU Li Ka Shing Faculty of Medicine, The University of Hong Kong , Hong Kong , China 3 Department of Laboratory Medicine, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine , Guangdong , China 4 Research Centre of Translational Medicine, The First Affiliated Hospital of Guangzhou Medical University , Guangdong , China 5 Department of Laboratory Medicine, Guangdong Women and Children Hospital , Guangzhou , China Background: Dengue virus is transmitted by mosquito around the tropical and sub-tropical regions. There was a large-scale dengue epidemic in Guangdong province, China during 2014 and around fifty thousands dengue fever cases, including six deaths, have been reported. In this study, we aimed to understand the clinical characteristics of hospitalized patients with laboratory-confirmed dengue virus (DENV) infection and determined the origin of the virus from the outbreak. Methods: We have summarized the data from 138 hospitalized patients who were laboratory confirmed for dengue infection in Guangzhou city. Patients were classified as either non-severe dengue fever or severe dengue fever according to the guidelines from the WHO. Viral serotypes were determined by real time RT-PCR. Genetic sequences of the envelope and non-structural genes were amplified and analyzed from the serum samples of eleven patients. Results: Co-circulation of dengue serotype 1 and 2 were identified from the outbreak. Patients infected by serotype 1 or 2 showed similar clinical features. Patients with severe dengue fever showed prolonged hospitalization and significant impairment of organ functions. Four samples from serotype 1 and five samples from serotype 2 were closely related respectively and clustered with Guangzhou isolates from previous years. The remaining isolates of serotype 1 were related to viruses found in Malaysia, India, Bangladesh and Singapore. Conclusion: The phylogenetic grouping of Guangdong isolates suggests that dengue is no longer an imported disease in China. Analysis of the isolates obtained in this study together with the size of the outbreak are suggestive of endemic circulation in Guangdong province. Dengue; China; Clinical; Outbreak; Endemic Background Dengue virus is a mosquito-borne pathogen and mainly transmits around the tropical and sub-tropical regions. It belongs to the family of Flaviviridae and is an enveloped, positive sense single-stranded RNA virus with the size of around 11 kb. Infection of either one of the four serotypes causes mild to severe disease symptoms [ 1 ]. It is estimated that around 50 to 100 millions people were infected by the dengue viruses every year and over 100 countries are being affected [ 2, 3 ]. In mainland China, outbreaks of dengue fever mainly occurred in the southern area (i.e. Guangdong, Yunnan) [ 4, 5 ]. Dengue infection in China was first reported in Guangdong province in 1978. From 1978 to 1989, Guangdong province was suffered from several times of serious dengue outbreaks [ 6 ]. Up-to-date, all four serotypes have been identified in Guangdong province but DENV-1 is still the main serotype circulating in the area. It has been suggested that the outbreaks occurred in China were mainly initiated by the import cases from Southeast Asian countries [ 7 ]. Although cases of dengue infection have been identified in every year, China has not experienced any large DENV outbreak (more than 10,000 cases) since 1990 [ 8 ]. However, from July to November of 2014, there was an unusual large-scale dengue outbreak in Guangdong province. Around fifty thousands of dengue fever cases have been reported, resulting in six deaths. The objective of the study was to describe the clinical characteristics of hospitalized patients with laboratory-confirmed dengue infection and determine the origin of the virus from the outbreak. Methods Patients and sample collection Hospitalized patients diagnosed as laboratory-confirmed DENV infection at the First Affiliated Hospital of Guangzhou Medical University were included in this study. Dengue fever cases were confirmed either by real time reverse transcription-polymerase chain reaction (DAAN, China), dengue NS1 antigen ELISA detection (WANTAI, China) or the IgM/IgG capture ELISA kits (PanBio) from the serum samples of the suspected cases. At the time of enrolment and hospitalization, the subject’s clinical history, physical examination, hematological, biochemical and microbiological investigations were recorded. Presumed (...truncated)