Charles Gerba, professor of microbiology at the University of Arizona, said during his ongoing experiments he has found that bugs get onto a phone because it is so close to our hands and mouths.
When somebody lets a friend or a stranger use their mobile their bacteria easily gets onto the device too.
Gerba added that because mobiles are electronic some people are reticent about cleaning. Since they are just not part of our cleaning routine. But they should be wiped with an antibacterial substance every now and then.
Previous research has found that other things we assume are clean are in reality rather disgusting, the Daily Mail reports.
British scientists discovered that cash machines have similar levels of pseudomonads and bacillus, bacteria which are known to cause sickness and diarrhoea, as they found in public toilets.
Computer keyboards are also five times dirtier than the average lavatory seat.