Objective To explore the species of arboviruses causing febrile cases in Gengma, a county in the China-Myanmar border, in Lincang city, Yunnan province in 2019, and analyze the epidemiological and etiological characteristics of arbovirus infection retrospectively and provide evidence for the early diagnosis of febrile cases and the prevention and control of vector-borne diseases.
Methods Clinical data of febrile cases treated at designated hospitals in Gengma county from September to October 2019 were collected. Serum samples were collected from the cases and tested for viral antigens using a dengue virus NS1 antigen detection kit, and viral RNA was extracted for real-time fluorescence reverse transcription-polymerase chain reaction (RT-PCR) for the nucleic acid detection of dengue virus, chikungunya virus, and zika virus. Dengue virus-positive samples were further subjected to serotyping by real-time fluorescence RT-PCR. Samples with high viral loads were selected for amplification of target genes sequencing for phylogenetic analysis.
Results In 946 serum samples from local febrile cases, 104 were positive for dengue virus (10.99%), including 33 dengue virus-1, 21 dengue virus-2, 36 dengue virus-3, and 14 unspecified samples. The false negative rate of the dengue virus NS1 antigen detection test was 20.19%. Additionally, 43 samples were positive for chikungunya virus (4.54%), and 6 cases were positive for zika virus (0.63%). Sequencing of positive RNA by RT-PCR obtained 8 sequences of dengue virus-1 NS5 gene, with a similarity of 97.70% to 100.00%, belonging to genotype I and showing close homology with epidemic strains in Myanmar and other Southeast Asian countries in recent years. One sequence of dengue virus-2 NS5 gene was obtained, belonging to the Cosmopolitan genotype, and showing close evolutionary relationship with the imported strains from Singaporean in 2013. Four sequences of chikungunya virus E2 gene were obtained, with a similarity of 99.30% to 100.00%, belonging to the east/central/south African genotype and showing close homology with epidemic strains in Ruili city in the same year.
Conclusion In 2019, dengue fever, chikungunya fever, and zika virus disease co-spreaded in Gengma county, Lincang city, China-Myanmar border area. Chikungunya virus and zika virus were detected in local febrile cases for the first time, suggesting that it is necessary to immprove the diagnosis of vector-borne viral diseases such as dengue fever, chikungunya fever, and zika virus disease, optimize the detection protoccol for vector-borne virus infection and identify potential infection sources as much as possible for the effective prevention and control of vector-borne diseases in the China-Myanmar border area.
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