Coronavirus disease 2019 (Covid-19) has non-specific clinical and laboratory characteristics that might be similar to other viral infection including dengue. Two Covid-19 cases with 'false-positive' dengue serology have been reported in Singapore but no public health consequence was described. We describe a Thai patient with an initial diagnosis of dengue fever who was later confirmed to also infect with SARSCoV-2. The Covid-19 infection appeared to spread to one family member and one healthcare worker.