Dengue is a leading public health problem with a significant global burden, particularly in endemic countries, but studies of primary infections in travelers to dengue-endemic areas are limited. Imad et al. retrospectively examined a cluster outbreak in a group of 12 Chinese travelers (median age: 18 years) who had visited Bangkok, Thailand, in October 2017. Infections were detected within a 4-week window after their arrival. None of the affected individuals had a history of symptomatic dengue infection. 

All patients were positive for the DENV non-structural protein 1 antigen. Serology test – available for only two patients – confirmed a primary-type antibody response (positive IgM) in one patient. Six clinical isolates were identified as dengue serotype-1, with 100% nucleotide identity suggesting that these patients were infected with the same virus. Of nine individuals who were hospitalized, four developed dengue warning signs including hepatomegaly. 

All patients with warnings signs and 80% of patients without warning signs had relative bradycardia. For all 12 patients, leukocytes, neutrophils and platelets declined towards defervescence and were negatively correlated with day of illness. Lymphocyte count and hemoglobin and hematocrit levels were positively correlated with day of illness. This study confirmed a cluster of primary acute dengue infection. Primary symptomatic infections can be severe, leading to hospitalization and sometimes death.  

https://www.mdpi.com/2414-6366/6/3/152

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