Know your brand
Brands should be unique, and is not encouraged to at what others are doing and just basically copy whatever that works for them. Twitter also encourages brands to lead by example, and to "do the right thing."
Keep up to date with what's happening
Keep posted with the latest news and changes, and adjusting communication strategy as necessary.
Be thoughtful about tone of voice
Don't be snarky or sarcastic. Show empathy and understanding. A little humour here and there helps too.
Anticipate changes in customer behaviour
As expected, more people are telecommuting which means businesses are impacted hence Twitter advices brands to adjust policies in line with evolving needs whenever possible.
Major brands have implemented policy changes, including airlines temporarily waiving rebooking fees for this month. It's good business practice, as it's very important not just for business but for pretty much everyone to be dynamic and adaptable in this stressful time.
And personally, I suggest everyone to remain calm, never panic, trust only verified and legitimate news source, and educate oneself about the virus and its symptoms.