Until now, six different coronaviruses have been known in humans, the current coronavirus is now the seventh. They all cause - in different degrees of severity - diseases of the respiratory tract. In Germany, a number of coronaviruses have long been known to cause colds. On the whole, these are not serious diseases. However, in other countries there are or were two coronaviruses for which one must have more respect: SARS and MERS. The SARS virus was first observed in 2002 and has not been reported since 2003. It probably originally came into humans from bats via an intermediate host and then caused very serious respiratory diseases with a fairly high death rate. This virus was also very contagious and therefore spread worldwide within a few weeks. The other coronavirus for which also more respect is needed is the MERS coronavirus. MERS was first detected in patients on the Arabian Peninsula in 2012. It can be transmitted from person to person; the transmission from dromedaries to humans plays a major role. It also causes severe lung diseases, but is not quite as contagious as SARS.

The new corona virus that has now appeared for the first time in China is quite closely related to the SARS virus from 2003 and is therefore now called SARS-CoV 2.

Its sequence is very similar to the sequence of corona viruses found in certain occurring bats and pangolins in China. We therefore assume that SARS-CoV 2 originates from these bats and may have been transmitted to humans through detour via the pangolin.

At the beginning of the pandemic in spring 2020, the cases of illness and death reported due to the novel coronavirus had initially increased rapidly and the reports came from different regions: While most cases were initially reported from China, followed by Japan and Korea, larger outbreaks have subsequently occurred in northern Italy, Iran and the USA, as well as the UK. In Germany, too, the number of cases initially rose very quickly. During the summer months of 2020, the virus was more or less under control in most European countries and only spread at a low level. Meanwhile, the number of infections in North and South America, in Africa and on the Indian subcontinent increased rapidly. From late summer onwards, the increase in transmission accelerated in Germany. Since the beginning of 2021, there has been an increase in infections with variants of the original virus. These mutations appeared to be transmissible much more quickly. After an increase in the number of new infections in Germany in the spring, the number of cases dropped significantly towards the summer. Then the numbers rose again until they first stagnated in early autumn and then skyrocketed at an unprecedented rate. From early December to the end of 2021, the incidence declined slightly. With the spread of the new variant Omikron, the infection figures increased rapidly again from the beginning of January 2022. In mid-February, the federal government announced the peak of the fifth wave and, together with the federal states, agreed on a gradual opening plan. Since the end of March 2022, the infection figures fell sharply. At the beginning of June, the numbers rose again. The Omikron subline BA.5 has now almost completely displaced all other variants. In the winter of 2022/2023, however, other viruses such as influenza and RS are increasingly causing problems for people in all age groups, resulting in an above-average number of acute respiratory illnesses.

• The latest figures can be found at the Robert Koch Institute (RKI; in German).
• The current figures for Lower Saxony can be found here on the website of the state government (in German)
• For worldwide events, we refer to the figures from the WHO.

Severe courses of disease continue to affect most unvaccinated people in older age groups and those with pre-existing conditions that weaken the immune system. The incidence of hospitalization remains by far the highest among people over 80 years of age.

Yes. The booster vaccination can be administered as early as the completed 3rd month after completion of the basic immunization. This is nothing surprising, also some other vaccines have to be applied three times to achieve a good protection.

According to the current STIKO recommendation, the booster vaccination is recommended for everyone, but older or previously ill persons should definitely be given priority in the booster vaccinations. In addition, people who have been vaccinated with the Johnson & Johnson (Janssen) vaccine, which is given only once.

For children and adolescents aged 12 to 17 years, the STIKO recommends the booster vaccination within a time window of 3 to 6 months after the primary immunization. Children and adolescents with previous illnesses should receive a booster vaccination as early as possible.

An mRNA vaccine should be used for the booster. Both mRNA vaccines (Comirnaty and Spikevax) are fully equivalent in terms of efficacy and are licensed for booster vaccination. 

The new corona virus can be transmitted from person to person by droplet transfer and probably also by aerosols - similar to other viruses that cause respiratory diseases. So you don't have to be in very close contact with the infected person, but you do have to be reasonably close. While droplets found in the air we breathe or ejected when coughing, for example, fall to the ground relatively quickly, aerosols containing viruses can remain in the air longer and can also be spread over several metres. The distance rule of 1.50 m currently in force in Germany thus provides fairly good protection against an infection transmitted by droplets, not necessarily against aerosols. The recommendation or regulation to wear a face mask in closed rooms is primarily intended to ensure that infected persons do not spread droplets or aerosols in their environment or at least reduce this. It is likely that wearing a face mask also provides some protection for the uninfected mask wearer to inhale infected droplets.  

It is also believed that the virus can be transmitted by contact through hands, followed by contact with the nose, mouth or eyes through contaminated hands.

It is now well known that people who do not yet have symptoms can transmit the virus. This helps the spread of the virus. We assume that people infected with the virus can transmit the virus to others about 1-2 days before clinical symptoms appear. If no restrictive measures are taken (wearing a mask, staying away, finding infected people, quarantine, etc.), on average every person who excretes the virus will infect two to three other contact persons - so the virus has the potential to spread very quickly.

The main transmission path is droplet infection. These are the invisible, but still inhalable droplets that fall to the ground after about 1.5 meters. This is why the distance rule is so important. However, also possible as a contact infection and this means direct contact - when giving hands or hugging, for example, but the risk of infection is lower than when inhaling the droplets. Inhalation is the quickest way for the virus to get where it wants to go.

Recently, the virus could be detected on plastic and stainless steel surfaces even after more than a week - not viable, but at least capable of reproduction. However, this only applies under certain conditions: darkness and humidity. Of course it is possible to become infected via these indirect contacts - but the risk is comparatively very low. Washing hands and wiping surfaces is enough because the virus is extremely easy to denature or inactivate, and therefore quickly loses its biological functions.

Risk factors are an age of 65 upwards with underlying conditions of the respiratory tract and the cardiovascular system, diabetes, overweight and high blood pressure. People of middle age can also become seriously ill, although this is rarer. Young people become ill only slightly in most of the cases; unfortunately, there are exceptions in which young people also have died.

At the moment we are facing a virus that is currently untreatable. Also this time there will be considerations on possible vaccination strategies, but this will only help those who are not yet infected. That means, the treatment is limited to alleviating symptoms, i.e. to dampen strong febrile reactions with antipyretic drugs, to support the patient’s circulation and if breathing is difficult , oxygen is given.

In severe cases, patients are connected to a ventilator, which means that they are admitted to the intensive care unit in hospital. There they often have to be treated for a very long time, i.e. three to four weeks.

None of the drugs currently under public discussion, such as those for malaria, HIV or Ebola, are used by the MHH. These are all potentially effective, but the problem is that there are no reliable data on the effects and side effects of all these drugs in Covid-19 patients.

The big challenge for doctors and nurses is that this disease is different from those known to date. The course of the disease is extremely difficult to predict and is often wavelike - i.e. the patient is doing well and then suddenly the condition worsens again for a variety of reasons.

We differentiate between diagnostic tests and tests that tell us whether you have survived the disease. The classical diagnostic test is the one based on what is known as PCR (polymerase chain reaction), in which we can detect whether the virus is present in the nasal swab or in the deep respiratory tract swab. The peculiarity of COVID-19 disease is that after infection, one does not become symptomatic until the fourth or fifth day. The test itself usually does not become positive earlier than one day before the first symptoms appear. This means that one can be infected and the test is still negative for three to five days.

Any strategy of using individual tests to control the spread of infection is therefore not very promising.

The antibody test is there to see if you have lived through the disease. COVID-19 has a specialty here: the antibodies do not rise until very late after the disease has been overcome - and the weaker the disease, the slower and weaker the rise. Patients with mild and moderate disease therefore have considerably fewer antibodies than patients with severe disease.

We also have the problem that we still do not know whether the antibody tests are specific enough for the SARS-CoV-2 virus. It is possible that other more harmless corona viruses, which we have known for many years and which appear every autumn and often cause a cold, will cross-react with these antibody tests. So a positive antibody test would not show that you have lived through COVID-19, but that you have lived through some corona-related disease.

Many university institutions - including the MHH - are working to develop a more reliable antibody test. At the moment, however, the tests are purely an object of research. They are not suitable for statements such as "I was ill and can therefore move around unprotected".

 

The measures recently enacted in many countries to limit human contact are based on computational models that attempt to predict the course of the epidemic in a country. These very plausible models say that if we do nothing now and simply "let the outbreak run", we would have to reckon with more than half a million deaths for a population like that of Germany. The drama of this scenario is compounded by the fact that the majority of these deaths would occur within a relatively narrow period of a few months. One can imagine that our health system would be completely overwhelmed by this. The current situation in Italy shows that this is not entirely unrealistic. This drama is essentially due to three factors:

1. The new corona virus, SARS-CoV-2, is hitting a population that has not yet acquired immunity to this virus - it can therefore spread unhindered. This is different with the influenza virus, since - at least in the case of the seasonal influenza that comes every winter - many people have at least partial immunity.
2. The new coronavirus is highly contagious: without contact reduction measures, an infected person will probably infect an average of 2 to 3 contact persons; at the beginning of the pandemic in Wuhan, this figure was even higher. This figure is significantly higher than for seasonal influenza, which recurs every winter. With such numbers, one can imagine how quickly an outbreak explodes: One infected person becomes three, then nine, then twenty-seven, and so on.
3.  An infected person can pass on the virus to others 1 or 2 days before the symptoms appear, i.e. at a time when one does not yet know that one is infected. This makes it difficult to control the epidemic: if only people with symptoms are isolated, there are still those without symptoms who can pass on the virus.