TVNewser has heard from some MSNBC staffers concerned that Rachel Maddow, who announced on “Late Night with Jimmy Fallon” Monday night that she had swine flu, could have brought the virus into 30 Rock.

“A lot of people at MSNBC are not very happy about not being informed that someone in the office was infected,” writes a tipster. “Some of us have families and children.”

MSNBC spokesperson Alana Russo tells TVNewser, “Rachel was diagnosed and began treatment Sunday (August 23) and did not return to work until until Thursday (August 27) when she was cleared to do so by her doctor at which point she was no longer contagious.”

Maddow also contributed to MSNBC’s Kennedy coverage Friday, but left early to rest up.

We’re told Maddow, who hosted her show in the days leading up to her diagnosis, did not start feeling the effects of H1N1 until Saturday, August 22 which led to the doctors appointment the following day. No one at MSNBC has shown symptoms of H1N1.