Singapore "knew that the foreign workers would be a stress point" in its fight against coronavirus, said one diplomat, adding that it would have made little difference in containing the spike in numbers. Speaking to CNBC on Friday, the country's ambassador-at-large at the Ministry of Foreign Affairs, Chan Heng Chee, said that when the first case of an infected foreign worker was found in the country on Feb. 8, "no one in the world knew" about asymptomatic infections. Those who are asymptomatic are infectious even though they do not develop any symptoms. "On April 3, there were just 36 cases amongst the foreign workers. We did what we always do — we test, we track, and we quarantined them, but later it just exploded," Chan said.

Singapore is the densest city and the densest country in the world, well, barring Monaco ... dense cities have a problem dealing with epidemics, with pandemics. Chan Heng Chee Singapore's ambassador-at-large at the Ministry of Foreign Affairs

When the virus first spread throughout the world, Singapore was lauded globally for managing the outbreak well and keeping the number of infections low. But cases have soared in the last month. On April 1, Singapore had just around 1,000 cases, but within less than a month, it has spiked to more than 10,000. The majority of the explosion in cases has been attributed to an outbreak among its migrant worker population. On managing infection rates among the workers, Chan said: "Could we have moved people out earlier? We could have, but I don't think it would have made a difference in transmission, maybe not at this rate, because they would be going to work, they would be cooking together in communal activities, and they would be going to the mall."

Singapore, a tiny city-state with a population of 5.7 million people, is heavily reliant on migrant workers for construction and other sectors. Those workers often hail from countries including India and Bangladesh. Around 300,000 of them live closely together in dormitories, in conditions which allow for easy transmission of the virus, experts say. "Singapore is the densest city and the densest country in the world, well, barring Monaco. We are denser than Hong Kong, and dense cities have a problem dealing with epidemics, with pandemics," Chan said. The Southeast Asian nation stepped up measures in the past three weeks, which included closing schools and non-essential workplaces, in what the government calls a "circuit breaker." With the number of cases still high in recent days, those measures were further extended to June 1 and more non-essential services suspended, while tighter mobility restrictions were imposed, the government announced Tuesday.

Foreign workers are seen outside their dormitory rooms at Cochrane Lodge II, which was declared as an isolation area on April 16, 2020 in Singapore. Suhaimi Abdullah/Getty Images