The reason is that we're washing our mugs up using sponges that aren't cleaned or replaced anywhere near often enough. And when a dirty cloth spreads bacteria to a cup or mug, the bugs can live for several days.
"People are aware of the risk of germs in the restroom, but areas like break rooms have not received the same degree of attention," says Gerba.
"This study demonstrates that contamination can be spread throughout the workplace when office workers heat up lunch, make coffee or simply type on their keyboards."
In fact, research from the University of Salford has revealed that our computer and phone can carry a whopping 10 million bacteria - 400 times more than the average toilet seat.
The team suggests that we should all be washing our hands as regularly throughout the day, and using anti-bacterial wipes on your keyboard and phone.
Similarly, the risk of sipping poo bugs along with your coffee is solved easily enough by taking care of hygiene yourself. Always wash your cup thoroughly in hot water with a clean sponge - you may want to take it home each night - and use sanitiser on work surfaces to be on the safe side.
But you may be surprised to hear that you should be replacing your kitchen sponge as often as once a week if you want to stop it making things worse rather than better.
According to German researchers, microwaving or boiling a sponge or cleaning cloth doesn't get rid of all tummy bugs - and can even help them spread.
Alternatively, you could just pop out for a takeaway coffee every time...
Disgusting things hotel guests do
Disgusting things hotel guests do
Reddit user and hotel worker OliverJamesIX says he wishes guests would think about the employees cleaning up after them when checking in for dirty weekends. "The amount of times a guest will have requested something, needed something fixed in their room or asked for room service, only to decide to f*** straight after they put the phone down leaving me stuck outside the door with that extra set of towels or walking into a room to fix something and seeing more than I ever needed too. Also bins are provided in bedrooms for a reason. Stop leaving used condoms, lube packets, discarded toys just all over the bed and tables."
"We had guests open the mini bar fridge, drink the beer, p**s in the empty bottle, screwed/put the cap back on and went on their merry ways," said hotel worker MistahZig. "Next client (old gentleman with his daughter) took a swill of p**s that day. Thing is, we had no idea which previous clients did this, which sucked." He added: "From that day on, I always twist beers open near my ear so I can hear that satisfying 'tssss' sound, just in case."
Reddit user undisclosed_lemons learned that a friendly couple were disgusting: "I used to be a manager at a hotel in a small town, I saw all kinds of sick things! I had an old couple who used all the towels, hand towels, and wash clothes to wipe there a**! I would occasionally help the maids and clean the rooms close to the front desk and I found the towels all waded up in the corner covered in c**p. Thing was, I like talking to that old couple too! That job taught me that all people are gross or have gross habits."
yushoi said she was a hotel room cleaner and hated "when guests put used untied condoms in the toilet, under pillows, under the bed, on the tea and coffee tray.. basically anywhere."
One hotel worker, armored-dinnerjacket, complained of the sneaky and rather disturbing things that guests do, including "taking a shit in one of the drawers and leaving it there." Ugh!
"When I was a housekeeper, someone got blood all over the sheets in one bed in the room, made it up to look like it hadn't been used, and mussed up the sheets on the other bed," said user Lost_in_GreenHills. "I was supposed to leave a bed alone if it hadn't been used, so I didn't know about the bloody sheets and I didn't change them. The next guest in that room arrived at 1am and crawled into the bed and fell asleep without even looking at the sheets. She saw the blood in the morning and was furious."
Hotel employee JimmyCarterDiedToday said that "masturbating in ice buckets" is the most disgusting things hotel guests do.
"I worked at two different hotels and the amount of guests who don't flush the toilet has always astonished and baffled me," said Jilltro. "Do people think that flushing is so arduous that if they're on vacation they're taking a break from it? How is flushing a toilet not a reflex?"
Former bellboy and maintenance guy shimmyfizzle recalls "finding a t**d in our pool. How does someone not mention this? If it was a kid, there should have been an adult there to witness it. It was pretty hard to miss."
One former employee said: "I worked in hotels years ago and the amount of people who order room service and answer the door scantily clad is astonishing. It's your room guy, if you want to lie around with your balls out that's totally fine just please, we give you a robe, throw it on before opening the door."