My friend is in Shenzhen China and heard the airports are shut down until 6/6. His visa will expire

Has he already got the 2-month automatic visa extension? If not, he can extend his stay for extra two months.

If 5/20 is the expiration date of the current visa in the passport book, you have an additional 60 days automatic extension period. If the expiration date of 5/20 is for the automatic 60 day extension, you must either apply for a new visa before then (which will cancel the old visa even if it is still valid) or exit China. If you overstay any of the visa dates, there will be fines for each day up to 10,000 RMB total and you risk deportation and ban from reentry to China.