We absolutely do have laser diodes that can output green and cyan (520nm green diodes have been around for years, and 488/492nm diodes are newer but also avaliable), but yellow is still in a gap that we don't have any known way of making a diode for at the moment.

Think of every infected person as a new chance for the virus to mutate. There's likely to be tonnes of new variants emerge as a result of the huge surge in China.