The 51st Art Basel has been Postponed to September. Honk Kong edition allow potential buyers to browse and buy artworks directly online. 

art basel q1
Public Art Project on Tour in Basel, Manfred Kielnhofer, Design Miami / Basel
Art Basel, one of the art world’s biggest events, has been postponed as the coronavirus pandemic continues to spread all over Europe.
The Art fair in Switzerland, was due to take place in June (18th- 21st) but organizers said  that the decision to postpone was reached with the goal of both protecting the health and safety of their community, and ensuring that the fair will be attended by the largest possible number of collectors, curators, and arts professionals from the fair’s global network.
The 51st year edition of the fair will be probably be postponed to September and galleries may need some time to consider if they want to participate. There will be no costs associated for galleries that choose not to participate.
Similar scenario for the visitors who can use their tickets if already purchased  or cancel and receive a reimbursement.
In Switzerland there have been over 10,000 infections and 153 deaths as a result of the virus and the country has moved to restrict non-essential travel.
Only Swiss residents and citizens or people traveling for work-related or emergency reasons, will be permitted to enter.
The Swiss fair has an edition also in Hong Kong and Miami . Organizers had already arranged digital exhibiting rooms, which allowed potential buyers to browse and buy artworks from the Hong Kong fair directly online. 
Art Basel’s Miami Beach edition is still scheduled to happen in December 2020.
More info on the New York Times