Brief overview
- Description: Infection with germs through contact with other people or contaminated objects.
- Transmission routes: While a smear infection (also indirect contact infection) occurs indirectly via objects (e.g. door handles, keyboards, toilet seats, food), germs spread directly from person to person (e.g. via the hands) in the case of a direct contact infection.
- Diseases: Typical diseases caused by direct contact or smear infection include influenza, gastrointestinal infections, shigellosis (dysentery), cholera, typhoid and polio.
- Prevention: Wash your hands regularly, clean kitchen utensils thoroughly, do not touch your face with unwashed hands, strengthen your immune system, vaccinations
What is a smear infection?
In the case of a smear infection or contact infection, you become infected with pathogens either indirectly via contaminated objects or directly from an infectious person.
How are pathogens transmitted?
The basis of a smear infection or direct contact infection is contact with surfaces on which pathogens are present. These can be objects, for example, but also the skin of others and infectious people. A distinction is therefore made between two forms of transmission:
Direct contact infection (from person to person)
Direct contact infection occurs through direct physical contact from person to person. This happens, for example, when an infected or sick person sneezes into their hand and pathogens stick to the surface of the hand. If this person then shakes the hand of another person, they pass the germs on to them. If this person then touches their mouth, nose or eyes, the pathogens enter the body via the mucous membranes.
Smear infection (via surfaces/objects)
For example, an infectious person coughs and gets germs into their hand. They then use door handles, to whose surface the pathogens stick. If another person touches this contaminated surface, the germs get onto their skin. There they ultimately enter the organism via small skin injuries or by touching the mucous membranes of the eyes, nose or mouth.
Fecal-oral transmission
Smear infections are often caused by germs that are excreted in the stool. The smallest traces of infectious feces are transmitted to other people via surfaces (e.g. toilet seats, taps) and hands. Doctors also speak of so-called fecal-oral infections (“from the stool to the mouth”). Noroviruses and rotaviruses in particular spread in this way. They sometimes cause gastrointestinal symptoms such as nausea, diarrhea and vomiting.
Other examples of smear infections
People also sometimes catch germs from animals via smear infection, for example when they stroke the animal and then touch their face. Germs can also spread via children’s toys or magazines in hospital waiting rooms or doctors’ surgeries.
In general, people who live closely with other people (e.g. within the family) become infected via a smear or contact infection. People who have close contact with other people, such as in nurseries, schools or hospitals, are also more susceptible.
How long do germs survive on the surface?
For pathogens to be able to spread at all via smear infection, they must be able to survive in the environment for a long time. Viruses, bacteria and fungi survive on surfaces for different lengths of time. While some pathogens are barely infectious after just a few minutes or hours, others persist for several days to months. For example, the following survive on dry, inanimate surfaces:
- Adenoviruses 1 week to 3 months
- Noroviruses up to 7 days
- Rotaviruses up to 8 weeks
- Sars-CoV-2 about 4 days (possibly longer under optimal conditions)
- Salmonella up to 4 years
- Escherichia coli between 1.5 hours and 16 months
- Streptococci up to 6.5 months
- Staphylococci 7 days to 7 months
- Candida albicans up to 4 months
How long a pathogen survives depends, among other things, on the ambient temperature, the surface (e.g. glass, wood, steel, plastic) and the humidity. Viruses, for example, usually prefer cooler temperatures. Bacteria survive at both warmer and colder temperatures, depending on the species. They can also go into a kind of dormant state (spores) and persist for decades.
Which diseases are transmitted by smear infection?
Cold sores (herpes) can also be transmitted via contact infection or smear infection. For example, if you kiss a person with a cold sore or share dishes, you may become infected with secretions from the cold sore containing the pathogen.
The same applies to various types of conjunctivitis. In this case, infection occurs when the affected person touches their eye. Infectious secretions get onto his hand, which he uses to pass on the germs.
More rarely, bacteria such as streptococci and staphylococci are transmitted to other people via festering wounds. There are also some other infectious diseases that spread via smear infection. Typical viral diseases are, for example
- Warts (through HPV, also from one part of the body to another through contact and smear infection = auto-inoculation)
- Cytomegaly (CMV infection)
- Hepatitis A (in particular fecal-oral smear infection, via contaminated water and food)
- Polio (polio, mostly fecal-oral infection)
Diseases that spread via smear infection with bacteria include those already mentioned:
- typhoid fever
- paratyphoid fever
- Impetigo contagiosa (bark lichen, especially in children)
- Tetanus (wounds caused by foreign bodies contaminated with tetanus spores such as nails, wood splinters or similar or contaminated by soil containing spores)
- Some types of chlamydia (especially those affecting the eye)
Fungal skin diseases, such as athlete’s foot or nail fungus, and parasites that cause skin conditions such as scabies, also spread via contact and smear infection.
How can you prevent a smear infection?
There are several measures you can take to effectively prevent a smear infection.
Careful hand hygiene is the best and most effective protection against both direct contact and smear infections. The most important thing is to wash your hands regularly with soap and water. This already significantly reduces the germ load on your hands. Make sure you clean your hands particularly thoroughly:
- before and after you prepare or have prepared food.
- after you have blown your nose.
- after you have coughed or sneezed.
- after you have touched or stroked animals.
- when you have come home.
It is particularly advisable not to touch your face with your hands if you are unable to wash your hands, for example when you are out shopping. This will prevent any pathogens from entering your body via your hands when you touch your mouth, nose or eyes.
Hygiene in the kitchen is also important to prevent infection with germs. Always keep perishable foods such as poultry or raw eggs in the refrigerator (at a maximum of +6 degrees Celsius). Also clean kitchen utensils such as chopping boards and knives carefully after use.
Although vaccinations do not prevent smear infection, they do provide reliable protection against infectious diseases that spread this way (e.g. influenza, hepatitis A, HPV). The vaccine teaches your body to recognize the pathogens at an early stage and to ward off an outbreak of the disease.
It is also advisable to wear gloves and protective clothing, especially in medical facilities, to avoid catching the disease from infectious patients.
