Droplet infection

Tanja Unterberger studied journalism and communication science in Vienna. In 2015 she started her work as a medical editor at in Austria. In addition to writing specialist texts, magazine articles and news, the journalist also has experience in podcasting and video production.

More about the experts All content is checked by medical journalists.

A droplet infection is an infection with bacteria or viruses that are transmitted through small, infectious droplets. These then get into the air when an infected or sick person sneezes, coughs or speaks, for example. The droplets are then ingested by another person (e.g. by inhalation) and may trigger an infectious disease. Read here which pathogens spread in this way and how you can protect yourself from them!

ICD codes for this disease: ICD codes are internationally recognized codes for medical diagnoses. They can be found, for example, in doctor's letters or on certificates of incapacity for work. A37B26B05J00A48A36A38J10G01B08A15B06B01

Brief overview

• Description: Infection with germs (e.g. bacteria, viruses) via the air through small, pathogen-containing secretion droplets or tiny particles (aerosols)
• Way of transmission: Pathogens get into the air through small droplets when sneezing, coughing or speaking; Another person either inhales them or the droplets land directly on the mucous membranes (e.g. throat, nose, eyes).
• Diseases: Diseases that arise from a droplet infection include flu infections, influenza, Covid-19, herpes, chickenpox, whooping cough, scarlet fever, diphtheria, mumps, measles, rubella.
• Prevention: keep your distance from infected people, wear masks (e.g. with Covid-19), do not sneeze at or cough at other people directly (instead in the crook of your arm).

What is a droplet infection?

With a droplet infection, one is infected with germs through secretion droplets containing pathogens. These are mostly bacteria or viruses (more rarely fungi). The droplets usually come from the saliva, nasal secretions or mucus from the respiratory tract of a sick or at least infected person. Important: Even symptom-free, i.e. not sick people, can transmit pathogens.

Depending on the droplet size, experts differentiate:

• Droplets at least five microns in diameter
• Small droplets that are less than five micrometers in size (aerosols, droplet cores)

Larger droplets only remain in the air for a short time due to their size and weight. Aerosols, on the other hand, float there for much longer and can also spread over longer distances. Therefore, one speaks here of an actual airborne transmission (by air).

How are pathogens transmitted?

In an infected person, the pathogens first settle in the throat or in the respiratory tract and multiply. If this person sneezes, coughs, speaks or breathes, small, infectious droplets and particles from the respiratory tract are released into the air. People who are actually ill, i.e. people with symptoms, generally excrete more pathogens than people without symptoms.

The droplets are in turn inhaled by other people or get directly onto their mucous membranes - for example in the mouth and throat, in the nose or on the conjunctiva of the eyes.

They also land on objects (e.g. doorknobs, telephones) or other surfaces and stick there. If a person then touches them, the pathogens may reach the mouth or eyes indirectly via the hands and thus enter the body (so-called smear infection).

If the immune system does not fight off the pathogens early on, they will multiply and, under certain circumstances, cause an infectious disease.

Transmission via droplets (droplets larger than 5 µm)

Larger droplets are more than five micrometers (five thousandths of a millimeter) in diameter. They usually get directly onto other people's mucous membranes by sneezing or coughing. Because of their gravity, they sink within a short distance (usually about 1 to 1.5 meters). As a result, droplets of this size only stay in the air for a short time.

Transmission via aerosols (droplets below 5 µm)

Smaller droplet cores under five micrometers are to be distinguished from the larger droplets. These "suspended particles", also known as aerosols, are a fine mixture of solid or liquid particles such as droplet nuclei in a gas (ambient air).

These tiny, pathogen-containing particles escape easily when speaking, singing, screaming or just breathing. Due to their low weight, they often float in the air for several minutes to hours and can therefore accumulate, especially indoors. They are also more easily distributed over greater distances and, because of their small size, also get deeper into the airways.

The smaller the droplet, the longer it hovers in the air and also spreads over longer distances.

Whether and how fast the droplets and aerosols sink or float in the air does not only depend on their size. Other factors such as ambient temperature, humidity and air movements (e.g. wind) also play a role.

In general, the risk of a droplet infection in closed rooms in which many people are, such as schools, kindergartens, cinemas or public transport (e.g. underground trains or buses), is significantly higher: The distances between people are small, but at the same time it increases Dense droplet nuclei in the air rapidly.

The risk of becoming infected within a distance of about one to two meters from an infected person is greatest.

Which diseases are transmitted by droplet infection?

Primarily viral, but also some bacterial diseases spread via droplets. Infectious diseases that develop through droplet infection with viruses include, for example:

• Flu (influenza)
• Colds (flu infections)
• Covid-19
• chickenpox
• measles
• mumps
• rubella
• Ringlet rubella
• Three-day fever
• SARS

The diseases that spread through droplets containing bacteria include:

• diphtheria
• whooping cough
• Scarlet fever
• tuberculosis
• Meningitis (inflammation of the meninges, also viral)
• Legionnaires 'disease (Legionnaires' disease)
• pest
• leprosy

Epidemics and pandemics - when pathogens spread for a limited time in one place or globally - are in most cases triggered by pathogens that are transmitted by a droplet infection.

Whether a disease actually breaks out depends on various factors, such as the physical condition or the infectiousness of the pathogen. In addition, the amount of pathogen-containing droplets that a person receives often plays a major role. For this reason, medical staff, for example, are usually more at risk than other groups of people.

How can you prevent a droplet infection?

Infection via droplets and aerosols cannot always be avoided. However, there are some steps you can take to reduce the risk of infection.

Keeping your distance reliably protects against larger droplets in particular. So stay at a distance as best as possible when you meet someone who is sick.

Sneeze and cough etiquette: Sick people protect their environment by not sneezing or coughing at other contact persons directly. Instead, sneeze and cough into the crook of your arm. If time permits, ideally use a disposable handkerchief, which you then dispose of quickly. The best thing to do is to move away from people nearby or to turn away.

Protective masks can help to catch droplets and thus minimize the risk of infection for certain diseases, such as SARS or Covid-19. Larger droplets can be kept well away from surgical mouth and nose covers. For even more protection, especially against aerosols containing pathogens, it is better to use FFP masks (particle filtering half masks, mostly FFP2).

Safety goggles, face shields and other protective clothing are among the suitable measures against droplet infection, especially in medical facilities. The staff wears the visors as additional protection to the usual masks.

Regular intermittent and cross ventilation also prevents infection via droplet infection. Ventilate frequently, especially if people are staying in an interior for a longer period of time.

A strong immune system also helps to fight off pathogens quickly. In our article “Strengthening the Immune System” you will find helpful tips on how you can effectively support your defenses.

Vaccinations are a very important part of this. They train the immune system with regard to certain pathogens, such as chickenpox or measles. If the “real” germs then reach a person via droplet infection, the immune system can react quickly and ward off the outbreak of the disease.

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