As the alien craft departed...

...they were somewhat perplexed to find the place deserted. Nobody in cinemas, nobody eating out, no one in planes, deserted shops, empty streets. Then one of them coughed and sneezed. 

"I'm feeling a bit under the weather actually" said one.

"Bit crook myself" replied the other. "I'm regretting shaking tentacles with that orange president bloke, but I suppose before the transplant he was one of ours".