Why can't ACH transmissions happen immediately

Contagion and Transmission

The SARS-CoV-2 coronavirus is transmitted in normal social interaction among the population mainly via virus-containing particles that are released by infected people, especially when they cough and sneeze, as well as when breathing, speaking and singing. Depending on the particle size and properties, a distinction is made between larger droplets and smaller aerosols. The transition between the two forms is fluid. While larger droplets in particular sink to the ground more quickly, aerosols can also float in the air for longer periods of time and distribute themselves in closed rooms. When breathing and speaking, especially at high volume, aerosols are excreted. When coughing and sneezing, significantly more droplets are also produced. Transmission in the open air occurs seldom and has only a small share in the overall infection rate. If the minimum distance is observed, the possibility of infection is very low in the outdoor area due to the movement of air.

In principle, within a radius of one to two meters around an infected person, the probability of coming into contact with virus-containing droplets and aerosols is increased (see also question "What role do aerosols play in the transmission of the SARS-CoV-2 coronavirus?"). If you stay in small, poorly or non-ventilated rooms for a long time, the probability of transmission by aerosols can also increase over a distance greater than two meters. This is particularly the case when an infectious person emits a particularly large number of small particles (aerosols), stays in the room for a long time and the other people present inhale particularly deeply. Due to the accumulation and distribution of aerosols in the room, maintaining the minimum distance may no longer be sufficient to prevent infections. An example of this is singing together in closed rooms over a longer period of time, where there were sometimes high rates of infection. Heavy physical work with inadequate ventilation has also led to high infection rates, for example in meat processing plants.

Infection can occur if such virus-containing liquid particles reach the mucous membranes of the nose, mouth and possibly the eyes of another person. Transmission through smear infection via the hands, which come into contact with the oral or nasal mucosa and with the conjunctiva, cannot be ruled out in principle.

A transmission via surfaces cannot be ruled out, especially in the immediate vicinity of infected people. The SARS-CoV-2 coronavirus was also found in stool samples from those affected. It has not yet been conclusively clarified whether SARS-CoV-2 can also be spread via the chair.

(See also questions "How can I protect myself and others from infection with the AHA formula?" and "What recommendations and regulations currently apply to the wearing of masks?“).

Status: April 19, 2021 (# 3760)

According to current knowledge, the coronavirus SARS-CoV-2 is mainly transmitted directly from person to person, e.g. B. when speaking, coughing or sneezing. Both droplets and aerosols (finest airborne liquid particles and droplet cores), which can float in the air for a long time, play a role in the transmission, whereby the transition between the two forms is fluid. By maintaining a minimum distance of 1.5 meters, the impact of droplets and, to a certain extent, aerosols can be reduced (see also question "How is the coronavirus SARS-CoV-2 transmitted?“).

A transmission of the coronavirus SARS-CoV-2 by aerosols is possible in certain situations over longer distances, e.g. B. when many people come together in insufficiently ventilated indoor spaces and there is increased production and accumulation of aerosols. This happens especially when speaking at a higher volume, but also when singing or possibly also during sporting activity. An example of this is singing together in closed rooms over a longer period of time, which has already resulted in high infection rates in the past. Heavy physical work with insufficient ventilation, for example in meat processing plants, has already led to high transmission rates. In the context of the COVID-19 pandemic, it is therefore advisable to avoid such situations.

In general, aerosols can be reduced by regular ventilation or, in the case of ventilation and air conditioning systems, by exchanging the room air with the supply of fresh air (or by appropriate filtration) indoors (see also questions "What role do air conditioning systems and devices play in the transmission of the SARS-CoV-2 coronavirus?" and "How can I protect myself and others from infection with the AHA formula?"As well as the topic page" Ventilate regularly "). Maintaining a distance of at least 1.5 meters and avoiding large gatherings of people is also recommended outdoors in order to minimize contact with droplets and aerosols. Transmission of SARS-CoV-2 outdoors over distances of more than 1.5 meters has not yet been observed.

Status: 04/26/2021 (# 4288)

Even younger people without previous illnesses and children can become seriously ill with COVID-19 or suffer long-term effects. In the first COVID-19 wave in Germany, there were also cases without known risk factors in the younger age groups (0 to 39 years) who had to be hospitalized.

If your condition or that of your child does not improve during the first week of the COVID-19 illness or if it worsens over the course of the illness, it is imperative that you contact your family doctor or your pediatrician by telephone. If you need medical help outside of normal office hours, it is best to call the medical on-call service on 116 117. In emergencies (e.g. if you have acute shortness of breath), call 112.

Status: May 3rd, 2021 (# 4835)

The SARS-CoV-2 coronavirus is mainly transmitted via droplets or aerosols (see question "How is the coronavirus SARS-CoV-2 transmitted?“.) Aerosols can float in the air for a long time and accumulate in closed rooms, e.g. if several people come together in insufficiently ventilated rooms. In the open air, on the other hand, aerosols cannot accumulate because they are carried away by the air. There is only a small risk of getting infected if, for example, you stand opposite each other for a long time and talk. Transmission of SARS-CoV-2 outdoors over distances of more than 1.5 m has not yet been detected.

To protect against infection, a minimum distance of 1.5 m from other people should also be maintained outdoors and crowds should be avoided. If the minimum distance of 1.5 m cannot be safely maintained or a gathering of people cannot be avoided, a mask should be worn. In addition, it is important to adhere to the currently applicable regional and supra-regional regulations for protection against the coronavirus (see question "Which corona regulations currently apply in Germany?").

Status: 04/23/2021 (# 4820)

The SARS-CoV-2 coronavirus is mainly transmitted via droplets or aerosols (see question "How is the coronavirus SARS-CoV-2 transmitted?"). Some people become infected and the virus can initially multiply in the airways. But the immune system then apparently reacts so effectively and can fight the virus so successfully that there are no symptoms. Sometimes the symptoms are so unspecific, such as gastrointestinal complaints, that they cannot be associated with the coronavirus (see topic page "Infection with the coronavirus: symptoms and course of the disease").

This means that a person may well have been infected with the coronavirus and can also pass on larger amounts of the virus by breathing, speaking, etc. without him or her showing signs of illness or being noticed. It is therefore important that everyone act carefully and adhere to the AHA + L + A formula.

Status: March 31, 2021 (# 4758)

In general, the risk of transmitting SARS-CoV-2 from one person to another is highest over short distances and with prolonged contact. Do many people in z. B. small, poorly or not ventilated rooms for a long time, a transmission by small airborne particles, so-called aerosols, can take place over a distance greater than 1.5 m. Such aerosols can best be reduced or removed by regular ventilation (in the case of ventilation and air conditioning systems, by exchanging the room air with a supply of fresh air or by appropriate filtration) (see also question "What role do aerosols play in the transmission of SARS-CoV-2?"As well as the topic page" Ventilate regularly ").

A wide variety of (mobile) devices are currently offered as a possible measure, which are intended to effect cleaning or disinfection of the room air. The use of these devices is intended to prevent the transmission of SARS-CoV-2 indoors. Further information on the various techniques, such as the use of air filters, nebulization or radiation techniques, as well as the effectiveness of the air exchange can be found among others. in the statement of the Federal Environment Agency (UBA) "The risk of transmission of SARS-CoV-2 indoors can be reduced through suitable ventilation measures". In addition, the commission for indoor air hygiene at the UBA issued a position on November 16, 2020 on the subject of "Use of mobile air purifiers as a ventilation-supporting measure in schools during the SARS-CoV-2 pandemic".

In this context, however, it is important to emphasize: Even an efficient reduction of aerosols in the room air can reduce the risk of Short distance transmission, e.g. B. with face-to-face contact at a distance of less than 1.5 m not effectively decrease. In addition, some important issues remain unresolved, such as: B. the actual effectiveness in the practical application, the health safety of the substances or processes used or the adequate distribution of a disinfecting agent or the filtered / disinfected air in the entire room. The risk of indirect transmission via surfaces that are contaminated with droplets containing pathogens cannot be reduced by using such devices (see also the question “Should I use disinfectants at home?“).

It is important that the use of a certain device for cleaning or disinfecting a room cannot replace compliance with distance rules or the wearing of a mouth and nose cover and should therefore not lead to a feeling of "false security" (see also question "How can I protect myself and others from infection with the AHA formula?"As well as the topic page" Everyday life in times of Corona: Protection through AHA + L + A ").

Status: 11/24/2020 (# 4351)

In the transmission of the coronavirus SARS-CoV-2, aerosols (finest airborne liquid particles and droplet cores) play a role in addition to virus-containing droplets (see also the question: "What role do aerosols play in the transmission of the SARS-CoV-2 coronavirus?"). Therefore, according to the Federal Environment Agency, it is basically conceivable that the coronavirus could be spread through ventilation and air conditioning systems.

In the case of central ventilation and air conditioning systems, it is important to ensure that they are operated with the highest possible amount of fresh air and the lowest possible amount of circulating air. The lower the proportion of circulating air in such a system, the lower the risk of SARS-CoV-2 being transmitted via aerosols.

In the case of central ventilation and air conditioning systems, regular maintenance and control is also important, for example to avoid incorrect flow of the extracted air. Faulty flow occurs when the extracted air can reach other areas of the building or the supply and exhaust air are not clearly separated from each other.

If it is not possible to increase the proportion of fresh air in the supply air, it is advisable to equip circulating air systems with additional filter stages for high-performance particulate filters (HEPA - H 13 or H 14) and to ventilate them additionally.

According to the Robert Koch Institute - in addition to regular ventilation - in air conditioning systems, an exchange of the room air with the supply of fresh air or appropriate filtering can reduce aerosols in the interior.

Decentralized air conditioning units, which are only used in individual rooms of an apartment, for example, do not spread viruses to other rooms, but the air currents can distribute aerosols faster and more evenly in closed rooms. Therefore, the operation of these devices with regard to the transmission of coronaviruses under certain conditions is not uncritical according to the assessment of the Federal Environment Agency. This is particularly true in rooms to which no or only a small amount of outside air is supplied.

Status: 11/13/2020 (# 4286)

The SARS-CoV-2 coronavirus is similar to other coronaviruses for which it has been shown that water is not a relevant transmission path. So far, according to the World Health Organization (WHO), there is no evidence that the coronavirus SARS-CoV-2 is transmitted via water.

In Germany, drinking water goes through a multi-stage purification process. As a result, drinking water is very well protected against viruses, including coronaviruses. A transmission of the coronavirus SARS-CoV-2 via the public drinking water supply is therefore highly unlikely according to the assessment of the Federal Environment Agency based on the current state of knowledge. This also applies to the transmission through pool water in indoor or outdoor pools, which is subject to constant treatment. Even in bathing waters in nature, no relevant concentrations of SARS-CoV-2 that could cause an infection are to be expected. Basically, however, people who suffer from an acute respiratory infection or diarrhea should not bathe in order not to endanger other bathers.

For swimming pools and bathing lakes, the current corona regulations for public life must be observed (see also the question "Which corona regulations currently apply in Germany?"). In swimming pools or when staying at bathing lakes, the rules of hygiene and behavior must be strictly adhered to in order to reduce the risk of transmission of the SARS-CoV-2 coronavirus from person to person.

Further information on the transferability of the SARS-CoV-2 coronavirus via water can be found at the Federal Environment Agency.

Status: 11/13/2020 (# 4278)

There is no evidence of transmission by mosquitoes.

Status: 04/03/2020 (# 4247)

The Friedrich-Loeffler-Institut provides recommendations for dealing with pets and answers to frequently asked questions.

The FLI is the Federal Research Institute for Animal Health and deals, among other things, with the protection against infections that are transmitted between animals and humans (zoonoses).

Status: 04/27/2020 (# 4245)

Infected people can infect others a few days before they develop symptoms (presymptomatic). A relevant proportion of the infections occurs within one to two days before the infected person shows signs of illness.

Some of the infected people develop no symptoms at all (asymptomatic). Also these infected people without signs of illness, i. H. People who do not get sick at all can transmit COVID-19; however, they probably play a subordinate role in the transmission of the SARS-CoV-2 coronavirus.

Status: 18.09.2020 (# 4248)

The incubation period, i.e. the duration from infection to the onset of the disease, is an average of five to six days for the SARS-CoV-2 coronavirus. Various studies have calculated that 95 percent of those infected had developed symptoms after 10 to 14 days.

The period from becoming infected or infected to the point in time at which one is contagious varies greatly. The highest contagion is around the period in which the own symptoms arise. However, there is also a risk of infection days before symptoms appear (presymptomatic). A relevant proportion of people are infected one to two days before the onset of the disease. However, from individual observations it can be concluded that an infection of others could possibly already occur on the day after one's own infection or even on the same day.

Presumably there are also transmissions from people who are infected and contagious but do not become ill themselves (asymptomatic transmission). However, these infections are likely to play a minor role.

Status: December 11th, 2020 (# 4249)

The exact period in which a person infected with the SARS-CoV-2 coronavirus can infect others has not yet been clearly defined. What is certain is that the contagion is greatest in the period around the onset of the symptoms and that a significant part of the transmission occurs before the appearance of the first symptoms. It is also certain that the infectiousness usually decreases in the course of the disease. In the case of mild to moderate illness, the possibility of infecting others is significantly reduced after more than ten days from the onset of the symptoms. In the case of severe illnesses and the presence of an immune deficiency, those affected can be contagious for much longer.

The decision as to whether a person is considered recovered and no longer contagious is made by the responsible health department (see also question "When can I leave quarantine or isolation at home?“).

Status: December 11th, 2020 (# 4250)

On my own behalf

There are currently a large number of unanswered questions about the transmission, duration of illness and protection options against the SARS-CoV-2 coronavirus, for which there are no sufficiently scientifically reliable data or studies due to the novelty of the pathogen. You can find the current state of knowledge in our comprehensive FAQs, which are updated regularly. Therefore, please use our FAQs for your information.

If you have any further questions, please contact infektionsschutz (at) bzga.de.

Please note that the Federal Center for Health Education (BZgA) is not a clinical institution. That is why we do not offer any individual medical advice or recommendations on diagnoses and therapy. Many factors are important for medical advice that can only be adequately taken into account in personal contact with your doctor or the local health department.

Last update of this page: 07.05.2021