Monitoring arbovirus in Thailand : surveillance of dengue, chikungunya and zika virus, with a focus on coinfections

Infections caused by arboviruses such as dengue virus (DENV), chikungunya virus (CHIKV), and Zika virus (ZIKV) frequently occur in tropical and subtropical regions. These three viruses are transmitted by Aedes (Ae.) aegypti and Ae. albopictus. In Thailand, the highest incidence of arbovirus infection and the high circulation of Aedes mosquito mainly occurs in the Southern provinces of the country. Few studies have focused on the incidence of co-infection of arboviruses in this region. In the present study, a cross-sectional study was conducted on a cohort of 182 febrile patients from three hospitals located in Southern Thailand. Surveillance of DENV, CHIKV and ZIKV was conducted from May to October 2016 during the rainy season. The serological analysis and molecular detection of arboviruses were performed by ELISA and multiplex RT-PCR respectively. The results demonstrated that 163 cases out of 182 patients (89.56%) were infected with DENY, with a predominance of DENV-2. Among these DENY positive cases, a co-infection with CHIKV for 6 patients (3.68%) and with ZIKV for 1 patient (0.61%) were found. 19 patients out of 182 were negative for arboviruses. This study provides evidence of co-infection of arboviruses in Southern Thailand and highlight the importance of testing DENV and other medically important arboviruses, such as CHIKV and ZIKV simultaneously

Molecular epidemiological study of hand, foot, and mouth disease in a kindergarten-based setting in Bangkok, Thailand

Hand, foot, and mouth disease (HFMD) is a contagious childhood illness and annually affects millions of children aged less than 5 years across the Asia-Pacific region. HFMD transmission mainly occurs through direct contact (person-to-person) and indirect contact with contaminated surfaces and objects. Therefore, public health measures to reduce the spread of HFMD in kindergartens and daycare centers are essential. Based on the guidelines by the Department of Disease Control, a school closure policy for HFMD outbreaks wherein every school in Thailand must close when several HFMD classrooms (more than two cases in each classroom) are encountered within a week, was implemented, although without strong supporting evidence. We therefore conducted a prospective cohort study of children attending five kindergartens during 2019 and 2020. We used molecular genetic techniques to investigate the characteristics of the spreading patterns of HFMD in a school-based setting in Bangkok, Thailand. These analyses identified 22 index cases of HFMD (symptomatic infections) and 25 cases of enterovirus-positive asymptomatic contacts (24 students and one teacher). Enterovirus (EV) A71 was the most common enterovirus detected, and most of the infected persons (8/12) developed symptoms. Other enteroviruses included coxsackieviruses (CVs) A4, CV-A6, CV-A9, and CV-A10 as well as echovirus. The pattern of the spread of HFMD showed that 45% of the subsequent enteroviruses detected in each outbreak possessed the same serotype as the first index case. Moreover, we found a phylogenetic relationship among enteroviruses detected among contact and index cases in the same kindergarten. These findings confirm the benefit of molecular genetic assays to acquire accurate data to support school closure policies designed to control HFMD infections

Clinical trial of oral artesunate with or without high-dose primaquine for the treatment of vivax malaria in Thailand.

We studied prospectively 801 Thai patients admitted to the Bangkok Hospital for Tropical Diseases with acute, symptomatic Plasmodium vivax malaria to determine the optimum duration of treatment with oral artesunate and the safety, tolerability, and effectiveness of a high dose of primaquine in prevention of relapse. Patients were randomly assigned to one of four treatment groups: 1) a five-day course of artesunate (Group A5); 2) a seven-day course of artesunate (Group A7); 3) a five-day course of artesunate plus a 14-day course of high-dose primaquine (0.6 mg/kg, maximum dose = 30 mg) (Group A5 + P); and 4) a seven-day course of artesunate plus a 14-day course of high-dose primaquine (Group A7 + P). During 28 days of observation, P. vivax reappeared in the blood of 50% of those who received artesunate alone (Groups A5 and A7), compared with none of those who received primaquine (Groups A5 + P and A7 + P; P < 0.0001). Adverse effects were confined to the 13 patients with a deficiency for glucose-6-phosphate dehydrogenase; high-dose primaquine (0.6 mg/kg of base a day) had to be stopped in four (31%) patients because of a significant decrease in the hematocrit. The combination of five days of artesunate and 14 days of primaquine is a highly effective and generally well-tolerated treatment regimen for vivax malaria in Thailand