BGMEA on Tuesday said of the workers, 48 persons tested positive for COVID-19, five are yet to be tested, one of the workers is waiting for the result while another one has recovered.
Of the 55 workers, 43 are male while 12 are female.
BGMEA said COVID-19 patients are facing social problems from their neighbours.
Also read: Reopening factories a premature decision: Experts
Bangladesh's thriving readymade garment sector is the second largest exporter of RMG goods after China and contributes to more than 80 percent to the country's foreign exchange earnings. The RMG sector employs more than four million people, mostly women.
Until April 29, BGMEA reported suspension or cancellation of orders amounting to $3.18 billion, affecting an estimated 2.28 million workers.
Also read: BGMEA requests its members not to sack workers in May
Apparel factories were shut days after the government announced general holidays to curb the spread of coronavirus in late March. Health experts criticised the government's decision to reopen factories, saying the 'premature' move could trigger coronavirus outbreak in the labour-intensive sector.