I think the co-workers are confused, but not totally off the mark. Chickens, along with just about every other animal we choose to keep around us can harbor zoonotic (meaning can be transmitted to humans) disease- but the problem is not that common in home flocks where decent sanitation is practiced.
Chickens can carry and get sick from many viruses and bacteria, most of which are fairly host specific. The before mentioned virus (marek's) is a herpes virus, but there is no documented jump to people. Cats have their own herpes virus too, which also does not jump to people. The H5N1 strain of avian influenza is a major zoonotic concern, but it is not in the US (yet). People can get a mild infection from Newcastles. Chlamydophylia psittaci/chlamydophilosis (aka psittacosis aka parrot fever) may be why they are saying STD, as the genus also contains the chlamydia that causes the human STD- BUT it is not the same organism. People can get psittacosis, but it is not common- and it is not an STD, is is respiratory. Salmonella, clostridia, erysipelas, TB are public health risks. Some are reportable diseases. Breathing in dust and dander from pets can be a problem for sensitive individuals, or those with underlying respiratory problems. People who have chronic respiratory problems & people who are immunosupressed for any reason, or caring for those who are- should talk to their human doctor about specific risks to them when taking care of chickens/dogs/horses/turtles ect. For the average joe, chicken keeping can be very safe- but just practice general good husbandry & sanitation. Hand washing, dust mask if cleaning coops ect. Most diseases from pets/animals are fecal-oral (accidental ingestion of poop- fingers in mouth with unknown small amt of poop on them, or eating unwashed veggies, raw egg, cutting board contamination), respiratory exposure, or into an open wound on the hand. Therefore washing up, dust masks, and covering up of wounds before playing in the chicken coop will dramatically decrease the possibility of zoonosis.
Chicks in the house is not much different than chicks outside, except there is a need for more washing and dust control.....
I keep my chicks in the house too....