E could stand for e.coli in your office. Tests conducted for the Herald on Sunday revealed computer keyboards are rife with bacteria, with "e" the filthiest letter.
Swabs taken by University of Auckland microbiologist Sarah Jennings show a big concentration of germs on the most common character in the English language.
Experts blamed "desktop dining" and lack of toilet hygiene for the phenomenon, and warned it was a way to spread diseases around the office.
Research at the University of Arizona last year found the average office desktop harboured 400 times more bacteria than the average office toilet seat. It also found women had up to four times as many germs around their work area as men.
British consumer magazine Which? tested 33 keyboards at its London HQ and found four were a potential health hazard, and one harboured five times more germs than one office toilet seat.
Jennings carried out tests at two Auckland sites for the Herald on Sunday, an office in Ponsonby and an internet cafe in the CBD.
She placed the swabs in a sealed container before incubating them overnight to allow time for bacterial growth.
Her results weren't as conclusive as the overseas studies, but she found enough germs to underline the need for office hygiene.
Jennings said bacteria could be good in the right place, such as e.coli in your intestines. "But if it gets in your eye or a deep cut, those types of infections can lead to death."
Auckland medical officer of health, Dr Greg Simmons, said a dirty keyboard was a sure transmitter of diseases including gastro-enteritis and respiratory infections, such as flu.
He said keyboards were prone to contamination because one-in-five men and one-in-10 women don't wash their hands after using the toilet.
Simmons said people should wash their hands for 20 seconds and dry them for the same amount of time.
He also blamed germs on office eating - a habit he was not immune to.
"I had a look at my keyboard the other day and it's filled up with a whole range of crumbs."
The owner of the Ponsonby office tested by the Herald on Sunday agreed.
"A lot of us eat and work at the same time, we don't always get away, we're almost living at the desk."
Milan Usal, of The Computer Cleaning Company, was not surprised by the results. He told the Herald on Sunday workers were "in the world of desk-top dining".
One city office was so dirty every keyboard had to be cleaned three times. "It was unbelievable," said Usal.
"What should have been a three-hour job instead took all day."