Evidence of Chikungunya virus seroprevalence in Myanmar among dengue-suspected patients and healthy volunteers in 2013, 2015, and 2018

INTRODUCTION

Chikungunya virus (CHIKV) is a mosquito-borne virus known to cause acute febrile illness associated with debilitating polyarthritis. In 2019, several institutions in Myanmar reported a CHIKV outbreak. There are no official reports of CHIKV cases between 2011 and 2018. Therefore, this study sought to determine the seroprevalence of CHIKV infection before the 2019 outbreak.

METHODS

A total of 1,544 serum samples were collected from healthy volunteers and patients with febrile illnesses in Yangon, Mandalay, and the Myeik district in 2013, 2015, and 2018. Participants ranged from one month to 65 years of age. Antibody screening was performed with in-house anti-CHIKV IgG and IgM ELISA. A neutralization assay was used as a confirmatory test.

RESULTS

The seroprevalence of anti-CHIKV IgM and anti-CHIKV IgG was 8.9% and 28.6%, respectively, with an overall seropositivity rate of 34.5%. A focus reduction neutralization assay confirmed 32.5% seroprevalence of CHIKV in the study population. Age, health status, and region were significantly associated with neutralizing antibodies (NAbs) and CHIKV seropositivity (p < 0.05), while gender was not (p = 0.9). Seroprevalence in 2013, 2015, and 2018 was 32.1%, 28.8%, and 37.3%, respectively. Of the clinical symptoms observed in participants with fevers, arthralgia was mainly noted in CHIKV-seropositive patients.

CONCLUSION

The findings in this study reveal the circulation of CHIKV in Myanmar's Mandalay, Yangon, and Myeik regions before the 2019 CHIKV outbreak. As no treatment or vaccine for CHIKV exists, the virus must be monitored through systematic surveillance in Myanmar.

Seroepidemiological surveys of tick-borne encephalitis virus and novel tick-borne viruses in wild boar in Nagasaki, Japan

In Japan, tick-borne viruses such as tick-borne encephalitis virus (TBEV) and severe fever with thrombocytopenia syndrome virus have been identified in humans, animals, and ticks. In addition, novel tick-borne viruses have been isolated from ticks in Japan. This study aimed to determine the seroprevalence of TBEV and novel viruses, particularly Tofla virus (TFLV), Kabuto Mountain virus (KAMV), and Muko virus (MUV) in wild boar in Nagasaki, Japan. Enzyme-linked immunosorbent assays and neutralization tests were performed to detect antibodies against each virus. Wild boar serum tested positive for antibodies against KAMV, TFLV, and TBEV, but not MUV. This study revealed the seroprevalence of newly identified tick-borne viruses and TBEV in animals residing in the Nagasaki area. The seroprevalence of these viruses in sentinel animals may inform policies aimed at preventing tick-borne virus disease outbreaks.