HONG KONG—Hong Kong reported 1,347 new daily COVID-19 infections on Sunday, down from the previous day’s record, but the spread, with 2,000 more suspected cases, threatens the city’s overstretched healthcare system, authorities said. The surge in COVID-19 cases, the biggest test yet for Hong Kong’s “zero-COVID” strategy, comes a day after the government said China would help the city with testing, treatment, and quarantine capacity. Following the death of a four-year-old who had tested preliminary positive for the disease this week, the government said late on Sunday that children from the age of three would be eligible for vaccinations from Feb. 15. Authorities also warned food supplies into the city may be disrupted, after some cross-border truck drivers tested positive for COVID-19. Hong Kong imports 90 percent of its food, with mainland China its most important source, especially for fresh food. Consumers have felt shortages of some imported goods, including …