Many earlier coronavirus clusters were linked to nursing homes and crowded nightclubs. But public health officials nationwide say case investigations are increasingly leading them to small, private social gatherings. This behind-doors transmission trend reflects pandemic fatigue and widening social bubbles, experts say — and is particularly insidious because it is so difficult to police and likely to increase as temperatures drop and holidays approach…

“Earlier in the outbreak, much of the growth in new daily cases was being driven by focal outbreaks — long-term care facilities, things of that nature,” said Nirav Shah, director of the Center for Disease Control and Prevention in Maine, where cases have soared in the past two weeks. “Now, the kitchen table is a place of risk.”

In Maine, as in other states, case investigators are seeing a new and related pattern: People who are infected list more close contacts than they did earlier, making the work of contact tracers more time-consuming and complicated. From March through September, the average number of contacts identified in Maine coronavirus investigations was 3.5. In October, that rose to 5.8.

“We’ve all gotten used to our bubbles, but I don’t think we’ve really asked whether someone who’s in our bubble is also in another person’s bubble,” Shah said. “People’s bubbles are getting big enough to burst.”