When train driver Li Zanming heard of a plan to reopen a rail freight route to support Hong Kong in its fight against COVID-19, he decided to volunteer his services, even though it meant facing the risk of infection and being away from his family.

He now leads a team of drivers ferrying containers of rapid antigen test kits, protective suits, medical supplies and other necessities to the city every day.

Rail, road and water routes are being used to bring much-needed supplies to Hong Kong, with numerous grassroots heroes emerging as the city battles its fifth wave of the pandemic.

Even though the Chinese mainland is now facing a sudden surge in infections, these routes and supplies to Hong Kong are assured.

Along with the physical support being provided to the city, an "invisible bridge" linking residents across the border highlights true friendship at a time of adversity.

Prosperous development on the mainland is inseparable from Hong Kong's investment in business across the border and the city's efforts to help mainland companies go global.

For example, the neighboring city of Shenzhen, Guangdong province,－a landmark in the nation's reform and opening-up drive－has learned from Hong Kong's business model and drawn on the city's deep pockets for the past 40 years. Hong Kong investors account for some 85 percent of Shenzhen's total foreign investment.

In addition to economic exchanges, hundreds of thousands of travelers pass through checkpoints between the two cities every day at peak times.

Li, the train driver, witnessed these close cross-border bonds by operating passenger trains to Hong Kong before the pandemic.

The cross-border rail freight route first opened in 1962 to ensure prompt delivery of livestock supplies to Hong Kong, including pigs, cattle and sheep, but it closed around 2010, when such shipments were switched to road transportation.

The rail freight route reopened on March 2 to ease pressure, as some 30 percent of cross-border truck drivers were infected with COVID-19 or in quarantine.

The 20-kilometer journey from the Pinghu South National Logistics Hub in Shenzhen to the MTR Lo Wu Marshalling Yard in Hong Kong takes only 35 minutes, but Li and his crew spent at least six hours on each trip, including commuting between their dormitory and the rail station, customs clearance, examining the train, and disinfection work.

On March 9, the number of freight trains on the route was raised from one to two each day, so the crews now work from 6 am to about 7 pm.

Li was highly impressed when Hong Kong Chief Executive Carrie Lam Cheng Yuet-ngor and other officials welcomed his train and thanked the crew on the first day of the freight route reopening. "At that moment, I felt the responsibility resting on our shoulders," he said.

"My colleagues are very energetic and motivated to do their work with a sense of honor," he added.

Besides the drivers, each freight train run is assisted by the joint efforts of numerous organizations, including customs, immigration, shipping companies and pandemic prevention departments, Li said.