Hong Kong could see a surge of imported coronavirus infections when travellers arrive from the southern hemisphere over the summer, according to a top infectious-diseases expert in the city, who has called for testing to be made more widely available.Professor Yuen Kwok-yung of the University of Hong Kong, who has been advising the government on the pandemic, also said restrictions on public gatherings could be relaxed further as long as people acted responsibly by wearing masks and keeping…