ov 19 (Reuters) - Hong Kong"s Cathay Pacific Airways Ltd (0293.HK) has fired three cargo pilots who were infected with COVID-19 during a layover in Frankfurt, over an unspecified "serious breach" of crew rules while overseas, the South China Morning Post reported. The newspaper said on Thursday the company did not reveal the breach but a source said the pilots were suspected of leaving their hotel rooms in Germany. Cathay did not immediately respond to a request for comment. The incident led to more than 150 other Cathay employees, including pilots and flight attendants, and many household members and community contacts being sent to a government quarantine facility for three weeks, SCMP reported.Hong Kong has recorded barely any local coronavirus cases in recent months but authorities in the global financial hub have tightened up quarantine rules. Hong Kong is following Beijing"s lead in retaining strict travel curbs, in contrast to a global trend of opening up and living with the coronavirus. The city government hopes the tighter rules would convince China, its main source of economic growth, to gradually open its border with Hong Kong. After the pilot cases were reported last week, Cathay said it would step up compliance checks at overseas ports to ensure health and safety protocols were being strictly followed during layovers. All of Cathay"s crew have received COVID-19 vaccines and the airline said it would require a booster dose as well. Hong Kong"s strict rules, which include up to three weeks of hotel quarantine for arrivals, have led to a plunge in travel demand. Cathay said this week it operated in October at only 10% of the pre-pandemic passenger capacity and posted a 97.2% decline in passenger numbers from 2019. However, cargo demand has been far more robust and the airline achieved close to operating cash break-even for the period from July to October. Reporting by Jamie Freed in Sydney; Editing by Richard Chang