Nintendo Switch online services are temporarily down. Both the Nintendo eShop and online multiplayer services are not working. Nintendo's official Japanese language Twitter account confirms the downtime and that recovery work is being done.
Browsing to Nintendo's own network status page also confirms "unable to connect to the network service. Please try again later." It appears that the outage is worldwide and affects all Nintendo platforms including Switch, Wii U, and 3DS. From my own testing, I can confirm that I could not connect to the eShop but was able to play Rocket League online with no problem.
Xbox Live and PlayStation Network suffered brief issues as both networks are facing increased network strain as more people stay home due to coronavirus precautions. Steam, meanwhile, broke its concurrent users record with 20 million people last weekend.
This outage comes at the worst time as many people are being told to stay indoors and practice social distancing. This naturally leads to increased time spent on streaming video services and online multiplayer games. While it's not confirmed that increased server load is the cause for Nintendo's online outage, it is safe to assume that every streaming and gaming service will be feeling the demand in the coming weeks.