It’s important to know how long germs survive on surfaces and outside the body so you can protect yourself and others from infection. “Germs” are any infectious agents, including viruses, bacteria, fungi, and protozoa. The length of time they survive varies widely depending on the type of germ, the surface it’s on, and other factors. Take a look at how long some common germs survive.
- Germs include viruses, bacteria, fungi, protozoa, and some algae that cause infections and disease.
- Most viruses are active less than a day on surfaces or outside the body. They survive longest on hard, dry surfaces.
- Most bacteria survive a few hours to a day. They survive longest on porous, damp surfaces.
- Bacterial and fungal spores are inactive, but remain viable for weeks or years.
How Long Do Viruses Live?
Technically, viruses aren’t actually alive because they can’t reproduce on their own. So, the question is how long they remain active and infectious. Viruses remain infectious longest on hard surfaces, like plastic, glass, and metal. They lose activity quickly on porous surfaces, like fabrics and wood. Low humidity, low temperatures, and low sunlight exposure extend their viability. The ultraviolet radiation in sunlight is lethal to most viruses.
However, exactly how long viruses last also depends on the type of virus.
- The flu viruses is active about 5 minutes on hands and about 1 day on surfaces.
- Cold viruses remain infectious for about 1 week.
- Coronaviruses, which cause COVID-19 and other respiratory infections, last a few minutes to a few hours on porous surfaces, like cloth and paper, and up to 28 days on hard surfaces, like glass and stainless steel. Coronavirus dies within minutes in sunlight.
- Calicivirus, which causes stomach flu, lasts for days to weeks on surfaces.
- Parainfluenza virus, which causes croup, lasts 4 hours on porous surfaces and 10 hours on hard surfaces.
- The Variola virus, which causes smallpox, survives about 1 day outside the body.
- Herpes viruses survive at least 2 hours on skin.
- The HIV virus dies almost immediately outside the body or exposed to sunlight.
There is a difference between the length of time a virus remains active and how long it remains infectious. A virus isn’t necessarily infectious, even if it’s active, if there are too few particles to pose a threat to the immune system. For example, the flu virus survives for a day on surfaces, but it’s rarely infectious past the first five minutes outside of the body. Similarly, the cold virus remains active for a week, but it’s not typically infections after the first day.
How Long Do Bacteria Live?
Viruses last longest on hard surfaces, under dry conditions. On the other hand, bacteria do best on porous surfaces and humid conditions. Some bacteria produce spores. Spores survive years or even centuries and resist some common disinfection methods.
How long bacteria live depends on the type of bacteria:
- Escherichia coli (E. coli) and Salmonella typhimurium are two common causes of food poisoning. They live for a few hours to a day outside the body.
- Staphylococcus aureus (S. aureus) causes toxic shock syndrome, wound infections, and MRSA infections. S. aureus forms spores that survive weeks on clothing.
- Streptococcus pneumoniae and Streptococcus pyogenes are responsible for strep throat and ear infections. Streptococcus survives on stuffed animals and baby cribs at least 12 hours.
Some types of bacteria form microfilms on surfaces. The films help bacteria survive longer and resist disinfection. Mechanical cleaning (like wiping down surfaces) and dry conditions limit microfilm formation.
Other Types of Germs on Surfaces
Aside from viruses and bacteria, germs that make you sick include fungi, protozoa, and algae.
- Fungi include yeasts, mold, and mildew. Fungi die without water in 1 to 2 days. But, they form spores that last indefinitely. Keeping humidity low prevents spores from growing, while HEPA filters remove them from air circulation entirely.
- Protozoa and algae need water to live. But, some protozoa form cysts. These cysts don’t last as long as bacterial cysts or fungal spores, but they live for months in soil or water. Boiling and cooking temperatures kill protozoan cysts.
Minimize How Long Germs Live on Surfaces
So, if viruses survive different conditions than bacteria and other germs, how do you minimize how long they live on surfaces?
- Hand-washing and mechanical cleaning remove all types of germs. Simple soap and water is an excellent defense against pathogens.
- Sunlight and artificial ultraviolet light dramatically reduce how long germs survive on surfaces or in air.
- Bleach and alcohol kill germs. Chemical disinfectants don’t always kill spores and cysts.
- Washing fabric in hot water (especially with bleach) kills most germs. The heat of a clothes dryer also kills bacteria and viruses.
- Metals containing copper or silver are natural disinfectants, effective against bacteria, fungi, protozoa, and algae. Copper, brass, bronze, and sterling silver inhibit microbial growth. While viruses remain active on stainless steel and other hard surfaces, they are easy to clean and disinfect.
References
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- Fish, D.N. (2002) “Optimal antimicrobial therapy for sepsis.” Am. J. Health Syst. Pharm. 15;59 Suppl 1:S13-9. doi:10.1093/ajhp/59.suppl_1.S13
- Gibbens, Sarah (April 13, 2018). “What to Know About the Germs in Your Home.” National Geographic.
- Mahy, Brian W. J. (1998). Topley and Wilson’s Microbiology and Microbial Infections: Volume 1: Virology (9th ed.). Hodder Education Publishers.
- Marks, L. R.; Reddinger, R. M.; Hakansson, A. P. (2014). “Biofilm formation enhances fomite survival of S. pneumoniae and S. pyogenes.” Infect. Immun. 82 (3) 1141-1146. doi:10.1128/IAI.01310-13
- Riddell, S.; et al. (2020). “The effect of temperature on persistence of SARS-CoV-2 on common surfaces.” Virology Journal 17, 145. doi:10.1186/s12985-020-01418-7