The issues are dealt with more details, as it is expected that many of the safety precautions, as in the lockdown, are effective, but cannot run in the longer term so rigid. Moreover, not all measures have been effective. For everyone to learn more connections and decide where and how their adaptations are possible and where, depending on local conditions, one must be particularly careful, the topic is dealt with in a complex manner.

1. 1. Figures from the Robert Koch Institute RKI (Germany) on the COVID-19 pandemic 12.6.2020:

Main transmission pathway	Droplet infection/ aerosols
Age median (Germany)	49 years
Common symptoms	cough, fever, cold, disturbance of the sense of smell and/or taste, pneumonia
Risk	especially elderly (60+), pre-sick (prior illnesses)
Base reproduction number R0 how many people infect an infected person on average (at current immunity level)	2-3.3 (according to various studies) With such a basic reproduction number R0 2-3,3, on average each infected person infects about two to three people. This does not say anything about the degree of illness or the form of symptoms.
Incubation time mean (range)	5-6 days (1-14 days)
Manifestation index	56,8–86 %
Duration of hospitalization	on average at least 10 days
Percentage of hospitalized (Germany)	17%

2.  General comments in advance

Based on previous major evaluations, it is estimated that on average about 43% of those infected do not show any symptoms that can indicate aCOVID-19 infection. This can vary from region to region.  While in a high-risk area in Germany with a significant local population there were about 22% symptomless infected persons, in Italy and China partly 43% showed a no symptom (asymptomatic disease process) and on some cruise ships, this number was much higher (up to just over 80%).According to WHO evaluations of the data collected worldwide, very mild or no symptoms were seen in 80% of infected people.

In addition to the age of the infected (younger people remain significantly more asymptomatic),  many other factors also play a role.

Substantially this depends on the pre-existing diseases, but also on the current immune responses.  These are known to be influenced by various lifestyle factors.

This is also plausible to increase the risk of infections with severe histories and then rather expected long-term damage - or problems that arise later, such as brain defects with the increase in dementia, which usually show up in later age.

According to genetic analyses of more than 398,000 inhabitants in the UK, 28% had an ApoE4 genotype (risk gene for later Alzheimer's disease) and an increased risk of a severe course of COVID-19 infection with therapy needs in intensive care units was found in these people in particular.

The ApoE4 genotype is a genetic risk factor for later Alzheimer's disease. This genotype was found in 20% of the German population; this is estimated to increase the risk of Alzheimer's disease by twice as much in the strongest form (homozygous form). However, in addition to high cholesterol levels, various other lifestyle factors play a role, whether or not the disease  breaks out (the topic epigenetics).

The asymptomatic infected individuals are probably less infectious, but this does not mean that the infection of others is necessarily more harmless; it depends entirely on who they have infected.

In the course of the long-term studies on COVID-19, even more, risk factors will be identified, which will give a better assessment of the expression and disease course and possible late effects (complications) in the context of multifactorial coexistence.

3.  Which symptoms are common in COVID-19 infection

When symptoms occur, you often see the following in Germany:

Cough 49%,

Fever 41%

Sniffing 21%

Disturbance of the sense of smell and/or taste 14% (in international studies this has been described in about 50% of symptomatic persons)

Pneumonia (pneumonia) 3%

Other symptoms: sore throat, shortness of breath, headache and limb pain, loss of appetite, weight loss, nausea, abdominal pain, vomiting, diarrhea, conjunctivitis, rash, lymph node swelling, apathy, somnolence

După cum am menționat mai sus, între 22-43% dintre infectați sunt asimptomatici în Germania (în funcție de locație și structura populației). Conform evaluărilor internaționale, OMS preconizează cazuri ușoare sau asimptomatice la aproximativ 80% dintre persoanele infectate.

4. Transmission paths for COVID-19

COVID-19 droplet and aerosol transmission

In the general population, the main transmission pathway for COVID-19 is the absorption of virus-containing fluid particles through the airways (when breathing, coughing, sneezing, speaking, and singing or screaming).

When breathing as well as speaking, and even more when singing or even stronger when screaming, mainly small air-water particles (aerosols) are excreted, which can last longer in the air. Coughing and sneezing produce more droplets, which can contain a higher viral load, but also sink to the ground faster.

In general, the risk of infection via the droplets and aerosols within a radius of 1-2 m around an infected person is increased.

Especially in enclosed spaces, the aerosols can be better distributed. How long the droplets or aerosols remain floating in the air depends on a variety of other factors (e.g. temperature, humidity, air movement, etc.) in addition to the size of the particles. 

The risk of infection is even higher if:

• an infectious person emits especially many small particles (aerosols) and a person inhales particularly deeply at a short distance(typically when singing in the choir of the church, on the football arena with screaming fans; or int he fitness course there were increased infections). In the gym, virus spread is particularly common when athletes perform heavy exercises in which they have a heavy press or shock breathing.
• even a longer stay in small, poor, or non-ventilated rooms (office, restaurant, public transport) can increase the probability of transmission by aerosols even over a distance of more than 2 m if the persons there are exposed for too long and especially if no mouth-nose covers are worn.

Due to the enrichment and longer dwell time of the aerosols in the air, observance of the minimum distance of 2m may no longer be sufficient.

Effective air exchange can reduce aerosol concentration and thus the risk of infection in a room. Outdoor transmissions are rare overall, which is why there are differences in events or outdoor dining compared to indoor. If there is additional air movement in the outdoor area (via wind or ventilator) and the minimum distance is maintained, the transmission risk is additionally reduced (overall low).

Contact transmission of COVID-19 over surfaces

Transmission through contaminated surfaces is possible near the infectious person, but it is not the main pathway. Surfaces are more likely to inactivate the viruses. 

So far, there is still too little data and conclusions are drawn from studies with other COVID viruses (previous SARS COVID1 infections), as the tests concerning inactivation show similarities with the new COVID-19 strain (SARS-CoV-2).  

Note on: Infectivity Virus Activity or Inactivation (RKI Information)

The different inactivation kinetics on different materials also correspond to previous experiences with SARS-CoV-1, which remained infectious on paper, cotton fabric or disposable protective coats for 1-2 days at high viral load (106 / ml), with lower titers (104 / ml) only a few minutes to an hour. Due to the structural similarity of SARS-CoV-1 and COVID-19, similar testability is plausible for COVID-19. In principle, the duration of the reproductive virus depends on many influencing factors, such as ambient temperature and humidity. Surface sanitizers with proven efficacy, at least the "limited virucide" range, are suitable for inactivation. A study from the USA suggests that COVID-19could be partially inactivated by sunlight on surfaces. In one simulation, 90% of the virus particles in saliva were inactivated after less than seven minutes.

Eye-Blindfold (Conjunctiva) as entry gate of COVID-19

In a few infected patients with pneumonia, smears from the blindfold COVID-19 were positive (PCR positive). With the current data situation, this is not proof that there is an entry gate there, but for safety reasons, one should not touch the eyes.

Transmission from the mother to the child before or during childbirth or breastfeeding

There are only a few studies and case reports from China for transmission from the infected mother to her child (before and during childbirth as well as via breast milk). Although transmission cannot be ruled out during pregnancy, the transmissions appear to have taken place only after birth, since most babies were born without signs of disease. There was also no evidence of infection from breast milk. 

In infected newborns, the infection appears to have occurred more through the airways if the mother initially had no symptoms and did not wear oral-nose protection until after the onset of symptoms. The data is currently still insufficient to answer these and other questions about COVID-19 safely during pregnancy and lactation. 

Medical sector (doctor's practice, hospital)

All possible transmission paths are important in all medical sectors and must be prevented by appropriate measures. All areas where doctors or dentists who come into contact with the mouth-nose-throat room involve a risk, an even greater risk of infection if infectious personnel or infectious patients are present. To prevent transmission, special breathing masks (at least FFP2 better FFP3 protective masks) should be worn by the professional groups concerned in these activities. The usual surgical masks or often worn oral nose coverings only reduce the infection of other people but do not prevent the self-infection(this only prevents you from a certain extent if all people wear such mouth-nose covers). Particle-filtering half-masks (FFP2-3) are required for effective self-protection. 

4b. Transmission by asymptomatic/pre-symptomatic and symptomatic infected

An infectious person may not have developed symptoms at the time of COVID-19 transmission to another person and may never show symptoms even later (asymptomatic infection).

However, an increased risk of transmission seems to be assumed by infectious individuals who have already developed signs of disease(symptoms). These symptoms can be relatively subtle or non-specific, such as having only headaches and a stuffy nose. Such a phase with mild symptoms can be followed in 1-2 days by the more "typical" symptoms, such as fever or cough, but it can also remain with only the mild course. 

As a result of this mild and non-specific course, and because of the possibility of being completely unrelated to symptoms, a significant proportion of infected persons are infected in these 1-2 days of the infected persons before their onset of symptoms.

This supports the fact that COVID-19 can cause superspreaders that infect so many others. It is not yet known whether some people are particularly infectious, or whether the super-spreading events are crucial (e.g. parties in closed rooms with many participants and close contacts; or singing together of groups in rooms and too little distance; or cramped living and working conditions of wage-earners employed in butchery, where the cold temperature conditions in the workplace also favor COVID-19).

More severe diseases (symptoms) are also associated with higher infectivity, but it may also be that some people without stronger symptoms can spread more viruses than others. In addition to the super-spreading events, where there are more sudden multiple contagions, there is a lot of contagion in facilities (slaughterhouses and community shelters, or nursing homes and hospitals) where the infections spread over several days because absolute protection without total quarantine is difficult to achieve.

The proportion of those who have already infected others at the beginning, without clear symptoms, cannot yet be estimated exactly. However, it is assumed that a significant part of this is due to the figures for asymptomatic histories suggesting.

Some experts consider these chains of infection to be less risky if the rules of conduct have resulted in the protection measures being followed against the risk groups.

The infection chains within the other groups (especially younger people) generally remain without serious illnesses and even, relatively more often asymptomatic (a study in China showed even in 94% of children very mild or asymptomatic infection histories – but this can be very different from a region).

4c.  When and for how long is an infected person contagious? Incubation period

In addition to the fact that infected persons who never become ill themselves can infect others, one can also see in those who develop symptoms (these are usually more infectious), the risk of virus transmission to others up to 3 days before the first signs of the disease (one day before the symptoms of the disease it even seems to have quite a high infectivity, since the own immune system could not increase the virus defense sufficiently).

Some researchers suspect that asymptomatically infected people may even be infectious for more than 14 days. However, the WHO and the specialist societies set the incubation period (which is also the orientation for quarantine time in suspected cases) at 14 days.

The incubation period is the period from the contagion to the onset of the disease – it is on average 5-6 days and has a range between 1 - 14 days, with decreasing infectivity in the course of the disease. It should be emphasized again that in case of an infection, both in an asymptomatic or symptomatic course, already the 2-3 days before - so always in the phase still without symptoms - the contagion is a risk of infection. 

Infectivity is not to be confused with the incubation period; infectivity can also last much longer. On the study data, it is not possible to give a reliable indication of the duration (see information in the box below).

How long is one contagious?

In the case of patients, the quarantine may be necessary for longer:

RKI 26.06.2020 In addition to studies or case reports for the detection of propagable viruses, a literature review to determine the infectious period also included studies based on PCR tests (genetic virus analysis), tracking person contacts, and modeling of analyzes. The mean periods of infectivity derived from these studies varied considerably in some cases and are sometimes adopted shorter for asymptomatic infections and childhood. The severity of the disease is also likely to affect the duration of infectivity. On the duration of infectivity in the pre-symptomatic phase, a relatively good agreement between the studies was shown on average with 2days (range 1-4 days). Studies of infector/infected pairs support this assumption. Here, infection periods of an average of five and seven days with decreasing infectivity occurred after the onset of symptoms. Based on the data available so far and the influence factors not studied so far (e.g. disease severity) no reliable information on the duration of infectivity and in particular at the end of the infectious period can be derived.

4d.  Proof of infection

Diagnostics for the detection of an infection

RKI 3.7.2020: An untargeted testing of asymptomatic persons is usually discouraged due to the unclear significance of a negative result (snapshot only).

Tests are in any case also indicated in asymptomatic persons in the case of justified people of contact.

Besides, asymptomatic individuals have a point of preventive testing in the following cases:

• in the clinic area inpatients before/when admitted
• as well as for staff inpatient care
• for all persons (staff and residents) in care facilities for the elderly and persons, as well as in facilities for people with disabilities and disabilities

In general, the correctness of the result of diagnostic tests is also influenced by the spread of disease. The rarer the disease and the more untargeted it is tested, the higher the requirements for sensitivity and specificity of the tests to be used. 

A negative PCR result does not rule out the possibility of infection with COVID-19. False-negative results cannot be excluded, for example, due to poor quality of sampling, improper transport, or unfavorable time (to the course of the disease) of the sampling.

If a patient with reasonable suspicion of COVID-19 infection is tested negative in the initial PCR, a re-sampling and examination should be made with the laboratory. The most appropriate examination material depends on the time of withdrawal during the disease. In the case of deep respiratory infections, the sole testing of sample material from the Oro and Nasopharynx (mouth-nose-throat space) is not suitable for the exclusion of infection, since in this phase of the disease only material from the lower respiratory tract or stool in the PCR may be positive.

The samples should also be examined differentially for other relevant respiratory agents. The samples obtained by the patient should be preserved to allow further examinations in case of doubt.

Antibody evidence (indirect detection of infection))

Antibody evidence currently serves primarily infection epidemiological questions. For the detection of a seroconversion (first occurrence of pathogen-specific antibodies – i.e. immunological defenses) during acute infection, blood samples should be obtained at a distance of approx. 14 days. In the majority of patients, seroconversion takes place in the 2nd week after the onset of symptoms.