A joint research study between San Diego State University and the University of Arizona tested 90 offices in three cities and found more than 500 species of bacteria, about the same number found in previous studies of bathrooms and aircraft.
It was found that people in developed countries spend about 90 per cent of their time indoors, most of it working eight or more hours in an office without going outside. This makes the modern workplace the new human habitat, which harbours hundreds of different types of bacteria.
Researchers swabbed five surfaces - chairs, phones, computer mouses, keyboards and desktops - and discovered the highest concentrations of microbes were on chairs and phones.
The study, published in an online science journal, PLoS ONE, found humans were the main source of bacterial abundance in offices, with skin, oral and nasal cavities harbouring trillions of micro-organisms that can shed and accumulate in work spaces.
Australian National University infectious diseases specialist, Professor Peter Collignon, told Fairfax Media that certain microbes die off quickly while those that can reproduce can hang around for years.
''Some can live for quite a long period while others are more susceptible to drying,'' he said.
Men's offices had up to 20 per cent more bacteria than women's offices, the researchers found.
