Use New Living Atlas COVID-19 layers in ArcGIS Enterprise
ArcGIS Enterprise includes a locally installed collection of Living Atlas items which you can search and use when authoring web maps and apps. However, some of the recently added COVID-19 content that has been added to ArcGIS Living Atlas of The World will not be discoverable in the currently installed items. The reason is that these have come online recently, and therefore were not part of the Enterprise Living Atlas collection as last updated.
However, all Living Atlas content is discoverable via searching ArcGIS Online when authoring maps using the Enterprise Map Viewer. The key to finding this content is to discover them using an ArcGIS Online layer search.
For example, a search performed against Enterprise Living Atlas using "covid-19" yields no matches.
Since these are very recent layers and are not part of the ArcGIS Enterprise installation. However, these new Living Atlas layers can be discovered immediately by searching ArcGIS Online when making a map, since all Living Atlas layers are discoverable via ArcGIS Online. Follow these steps:
Step 1 – Open Map Viewer.
Step 2 – Click Add, then Search for Layers.
Step 3 – Choose ArcGIS Online.
Step 4 – Enter the search string.
Living Atlas content is identified by the blue globe symbol. Click the title to view the item details.
Step 5 – Click 
to add the layer to your map, or if you have opened the item pages click Add to Map at the bottom.
Tip: You can use the ArcGIS Living Atlas website to browse for coronavirus (and other) content, then copy and paste the exact title into your ArcGIS Online search above. Open the Browse tab and enter your search criteria.
For example, this search finds all Living Atlas layers for the United States that match the keywords "coronavirus," "covid-19, or "mobility."