It depends on the type of bacteria or virus, what kind of surface they are on and what the surrounding environment is like, for example, if it's hot, cold, damp or sunny.
Many different types of viruses can cause colds. The viruses can sometimes survive on indoor surfaces for more than 7 days. In general, viruses survive for longer on non-porous (water resistant) surfaces, such as stainless steel and plastics, than porous surfaces, such as fabrics and tissues. Although cold viruses have been shown to survive on surfaces for several days, their ability to cause an infection reduces rapidly and they don't often survive longer than 24 hours.
Most viruses which cause colds only survive on hands for a short amount of time. Some only last for a few minutes but 40% of rhinoviruses, a common cold-causing virus, are still infectious on hands after an hour.
Respiratory syncytial virus (RSV), another cold-like virus that can cause serious illness in children, can survive on worktops and door handles for up to 6 hours, on clothing, and tissues for 30 to 45 minutes and on skin for up to 20 minutes.
Flu viruses capable of being transferred to hands and causing an infection can survive on hard surfaces for 24 hours. Infectious flu viruses can survive on tissues for only 15 minutes.
Like cold viruses, infectious flu viruses survive for much shorter periods on the hands. After 5 minutes the amount of flu virus on hands falls to low levels.
Flu viruses can also survive as droplets in the air for several hours; low temperatures increase their survival in the air.
Parainfluenza virus, which causes croup in children, can survive for up to 10 hours on hard surfaces and up to 4 hours on soft surfaces.
There are many germs that can cause a stomach bug. They include bacteria such as E. coli, salmonella, Clostridium difficile (C. difficile) and campylobacter, as well as viruses such as norovirus and rotavirus.
Salmonella and campylobacter survive for short periods of around 1 to 4 hours on hard surfaces or fabrics. Norovirus and C. difficile, however, can survive for much longer. In one study, C. difficile was shown to survive for 5 months. Norovirus can survive for days or weeks on hard surfaces.
When someone with norovirus vomits, the virus is distributed in small droplets in the air. These droplets can settle on surfaces, causing the virus to spread, so it's important to clean surfaces thoroughly if someone in your home has norovirus.
Most bugs can be removed effectively by soap and water. To help prevent the spread of stomach bugs wash your hands thoroughly and regularly, particularly after going to the toilet, and prepare food safely.
The staphylococcus aureus bacteria that cause MRSA infections can survive for days to weeks on surfaces. MRSA bacteria can live on surfaces for longer than some other bacteria and viruses because they survive better without moisture. Generally, MRSA bacteria survive for longer on hard surfaces than on soft surfaces.
Herpes viruses from cold sores around the mouth can survive for 2 hours on the skin. If you have a cold sore, try not to touch it. If you do touch it, for example to apply cold sore cream, wash your hands immediately afterwards.