Buses and subways in Seoul, the normally crowded South Korean capital, were unusually quiet on Monday, and social media was filled with posts with the hashtag “work from home.” South Koreans work some of the longest hours in the world, and companies tend to frown on allowing employees to telecommute. This drastic departure from the conventions of corporate culture are a sign of how the country is scrambling to slow the spread of the novel coronavirus. The country’s public health authorities have for the past several days reported drastic increases in the number of cases here, with 231 new cases on Monday, bringing the total number to 833, with more than 11,600 people undergoing diagnostic testing.