Hong Kong reached the grim milestone of 1,000 coronavirus cases on Saturday as authorities urged the public to stay at home during the long Easter weekend after thousands flocked to beaches and the countryside the previous day.

Underlining the severity of the situation, a leading microbiologist said containing the outbreak before July was almost impossible as not enough people had developed immunity to the virus.

The warning came as the city recorded 11 new infections, the fewest since March 17, and the eighth consecutive day the number was below 30.

“If you take the seven day moving average, the general trend is a bit downward,” said Dr Chuang Shuk-kwan, head of the communicable diseases branch at the Centre for Health Protection. “I hope this is a persistent trend, not a temporary trend that could rebound.”

Recent travellers continued to be the main source of cases, with 10 of the latest coming from outside Hong Kong. The single local transmission involved the girlfriend of a 28-year-old man already confirmed to have Covid-19. She visited the All Night Long bar in Tsim Sha Tsui previously linked to a cluster of infections.

“Although it appeared there might be fewer imported cases, that might be due to fewer arrivals in the city,” Chuang said. “There could possibly still be local transmission chains in the community, so people really have to gather less.”

Given the long incubation period of the disease, the lower figures could not be taken as evidence the threat was receding, she warned. “I’m not sure about the coming trend, so we need to maintain vigilance.”

Far fewer people were out at top scenic spots around the city compared with Friday, when blue skies and sunshine lured families outdoors. The weather was less inviting, with overcast skies and a chilly breeze.

At Repulse Bay Beach, where about 1,000 people packed the shoreline the day before, only a few dozen people lounged on the sand, with a handful of swimmers in the distance and most groups maintaining a physical distance. Nearly everyone was wearing a mask.

Jonathan Lerivray, who works in the financial technology industry and was with his wife and two children, largely agreed with the government’s advice to stay home. But he said it was more important that people who ventured outside observed social distancing.

“We did decide to come today because the weather was not great and we knew there would be less people,” the 35-year-old said. “Still if it was packed, we would have hesitated because we have been influenced by the number of cases locally – at least in general – going down, and most of the new ones are from overseas. That does bring a sense of safety but not complacency.”

Along the Tsim Sha Tsui waterfront, the famed Victoria Harbour skyline was shrouded in a faint haze, and crowds of just a few dozen people were spacing themselves apart as they walked, jogged or sat admiring the view. Retail worker Ferris Chou, out with his girlfriend, said he accepted the government’s call but felt observing precautions while in public was sufficient.

But the 29-year-old said he expected the outbreak to worsen, and authorities would have to enforce stricter social rules on weekends and public holidays. “The measures so far are working because Hongkongers are sensible and sensitive,” Chou said, pointing to the general use of masks.

The K11 Musea was also less packed. Some parents and children wore masks as they enjoyed a display of giant Easter egg sculptures. Causeway Bay, however, remained busy, especially around the SOGO shopping mall, one of the biggest draws in the area.

To relieve pressure on the quarantine camps, the government has shortened how long some people must stay. Under the new arrangement that took effect on Saturday, 37 people who had spent 10 days at the centres were allowed to return to their residences for the final four days but they will continue to be monitored. Chuang said the measure, which would be introduced gradually, would need time before a significant number of spaces were freed up.

From Monday, all airport arrivals from the United States and Europe will also be required to undergo testing at AsiaWorld-Expo and await a negative result before they can leave, as long as the backlog remained manageable. Currently, only arrivals from ­Britain must wait at the centre for the all-clear.

The speed with which Covid-19 has spread around the world has caught nations off guard, but a new study led by microbiologist Yuen Kwok-yung from the University of Hong Kong has provided some insight into why. His research found the virus generated 3.2 times more viral particles than the severe acute respiratory syndrome within 48 hours and induced slower immune responses. “There is almost no possibility of containing the virus before July,” Yuen said.

Twenty-seven more patients were discharged and about 30 others were receiving Gilead Sciences’ experimental antiviral drug remdesivir as part of a clinical trial, said Dr Sara Ho Yuen-ha, the Hospital

Authority’s chief manager for patient safety and risk management. None had shown any serious side effects yet. “Some clinical doctors told us that the drug seemed to be effective in improving the fever of some patients,” Ho said. “But it’s just individual cases.”

A larger global number was needed to conclude whether the drug had statistical significance.

Twenty-six Hongkongers returning from Morocco tested negative for the coronavirus when they arrived in Guangzhou in Guangdong province. They will be tested again on April 15 when back in Hong Kong.