Top microbiologist Yuen Kwok-yung on Monday urged the government to check if outsourced workers had collected samples for coronavirus tests properly, warning it could be one of the loopholes in the city’s quarantine measures. His comment comes after a foreign domestic helper who had no recent travel history came down with a mutated strain of Covid-19. Tests showed the virus contracted by her is genetically identical to that found in a man who flew in from Dubai. Yuen said improper sampling by outsourced testing firms may lead to false negative test results, adding that officials should double check the samples. “One big problem is that staff might not have properly collected samples for nasopharyngeal tests. On the mainland, the swab is inserted far into the nasal cavity. It’s quite uncomfortable. But in Hong Kong, the swab is not inserted far enough,” he said. He added that rapid contact tracing is also needed to prevent another wave of infections. “We must understand the whole process to stop it from spreading in the community and learn a lesson how come there’s still a hole in our quarantine measures,” he said.