The International Maritime Organization (IMO) has set up a page on its website for Covid-19 advice, available at:
It contains a list of Circular Letters issued by Member states with Covid-19 related notifications. received from IMO Member States (updated weekly):
The update indicates that some states have issued guidance on extension of certificates. For example, Panama has extended for three months the validity of all statutory certificates (except for Conditional Certificates) expiring between March and May 2020. The update also details measures implemented by individual ports.