COVID-19 half a year later: What have we learned? | Science| In-depth reporting on science and technology | DW | 07.07.2020
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COVID-19 half a year later: What have we learned?

Six months have passed since SARS-CoV-2 became known worldwide. Since then, researchers have found out much about the virus and made progress in combating it. Here are the most important points.

Half a year ago, at the beginning of the second week of January, Chinese authorities made the first public announcement  that a new type of virus was rampant in the city of Wuhan.

Here is an overview of what has become known about the virus so far and how far medicine has progressed in the fight against SARS-CoV-2:

Origin of the virus

When the existence of the virus was announced, the first infection of a human by a vertebrate animal had apparently occurred several weeks earlier.

Initially, Chinese authorities seem to have tried to suppress any evidence.  To this day, it is not exactly clear when and where the virus jumped from animal to human.  Transmission from a bat to an intermediate host, perhaps a tanuki, and then to humans is considered likely and seems to be the origin of the pandemic that is still in full swing  today.

Coronaviruses under the electron microscope (picture-alliance/dpa/Center for Disease Control)

One of the first images of the novel coronaviruses from January 2020, since when research has gone much further

Appearance of the virus

Chinese virologists deciphered the genetic information of the virus in record time. On January 21, they published the genome structure and three days later a detailed description  of the virus. This enabled physicians and microbiologists worldwide to begin developing drugs and vaccines.

Typical of the virus are the spike proteins (ACE-2) located on its surface. These are crucial for binding to the host cell. That is why a large part of drug and vaccine development is focused on binding or blocking this protein or rendering it ineffective in some other way. 

Illustration of a coronavirus (picture-alliance/Newscom/CDC)

A model of the coronavirus: Most prominent is the spike protein (S) that gives the virus its crown-like appearance

Transmission

In the meantime, it has been established — among other things by a study  carried out by virologists in the city of Heinsberg, one of the first hotbeds of the disease in Germany — that the virus is particularly prevalent in the throat and lungs. The greatest danger of infection is — besides coming into direct contact with an infected person or touching a contaminated surface, known as smear infections — through aerosols. These spread particularly well through air-conditioning systems, such as those used widely in the meat industry. 

Closed rooms with many people in them are very dangerous. That is why lockdown measures, the closure of entertainment establishments and the cancellation of trade fairs and major events were very effective in containing the disease. 

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The largest chains of infection could be traced back to so-called superspreader events. 

The use of mouth-and-nose protection, i.e., face masks,  has now become established in almost all countries of the world. However, many medical professionals question whether most people are capable of using it in everyday life in such a way as to help prevent potential virus transmission.

What is most important is for people to wash their hands, keep their distance from others and air rooms thoroughly.

Even if some pets, such as cats, ferrets and golden hamsters, can become infected by humans, they do not play a significant role in infection chains.

Symptoms and risk groups

Initially, it was thought that the new virus was hardly more dangerous than seasonal flu. Now, however, physicians know better: The disease poses a threat similar to that of the devastating Spanish flu of 1918.  Although many people can get a SARS-CoV-2 infection without symptoms, others become very ill with COVID-19, the disease caused by the virus.

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Some groups of people are more often affected than others: People with previous illnesses, elderly people, people with blood type A and men are more at risk.

Pathologists who examined COVID-19 victims were able to confirm that high blood pressure, diabetes, cancer, kidney failure, liver cirrhosis and cardiovascular diseases are among the most dangerous preexisting conditions. In principle, however, a severe case of the disease can affect anybody, including young people. 

Read more: Coronavirus: What is the risk for asthma patients?

Course of the disease

Mild forms of COVID-19 can present like a cold. Typical symptoms are a sore throat, breathing problems and a loss of the sense of smell and taste.

In severe cases, however, a life-threatening multi-organ disease can occur.

This often leads to sepsis  — a frequently fatal overreaction of the immune system that attacks the infected person's own tissue and organs.

So how severely someone is affected by the disease depends to a large extent on how strongly his or her immune system reacts to the pathogen. 

Read more: Top 10 most dangerous viruses in the world

Treatment

At the beginning of the coronavirus pandemic, many patients with severe courses of the disease received artificial respiration (intubation) at an early stage and died all the same.

Now, however, intensive-care physicians have moved away from standard ventilation, because lung specialists have stressed that artificial respiration under positive pressure can do more damage than good to the lungs.

As long as patients are able to breathe on their own, they now receive oxygen without being connected to a respirator. Intubation is used as an option only in an extreme emergency.

In many cases, when the kidneys are severely damaged by COVID-19, dialysis is also necessary. Intensive care now also takes other damaged organs more into account.

The healing process can be accelerated in specialized clinics by the administration of antibodies from the blood of cured COVID-19 patients. These antibodies take up the fight against the virus in the body of the patient who received the donated blood.

As a rule, COVID-19 patients must undergo lengthy, individually tailored rehabilitation measures after their intensive medical treatment. These must also take into account their specific previous illnesses and possible organ damage.

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What is Remdesivir?

No convincing drugs yet

Remdesivir  is the only pharmaceutical drug that has been shown to shorten the course of the disease. This is why it is so hotly contested on the market. 

But it is not a miracle cure. It shortens the healing process by a few days in patients who receive oxygen, but it does not improve their chances of survival.

Doctors are also trying to use other drugs that are already on the market  to combat the coronavirus. These include the anti-inflammatory dexamethasone , the RNA polymerase inhibitor Avigan  and the malaria drug hydroxylchloroquine.  The efficacy and safety of the first two drugs has not yet been conclusively proven, and there are even strong doubts  about the third.

How far along is vaccine development?

At least 160 vaccine projects have now been launched worldwide (as of June 29, 2020) according to the German researching pharmaceutical companies. These are essentially divided into three vaccine types: attenuated vaccines, inactivated vaccines and gene-based RNA vaccines.

In the latter case, however, physicians are entering uncharted territory because no such approved vaccines are available. Both the Biontec and the CureVac  vaccines currently approved in Germany for combined Phase 1 and 2 trials are such RNA vaccines.

In addition, there is a tuberculosis vaccine  that has already been approved. This does not directly target SARS-CoV-2, but strengthens the basic innate immunity of humans. Researchers at the Max Planck Institute for Infection Biology in Berlin are currently trying to improve this vaccine genetically.

According to information from the WHO,  five vaccines were in Phase 1 human trials worldwide at the end of June 2020. Such trials test the safety of the vaccine. Seven are in combined Phase 1/ Phase 2 testing, where the immune response is also tested, and only one vaccine  is already in Phase 3, where the aim is to prove its effectiveness against the pathogen in practice.

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Vaccine efforts a mix of competition and cooperation

When will the vaccine finally come?

Optimists hope that a usable vaccine will be on the market by the end of the year. Others are talking about next year. In fact, it is not yet possible to say whether and when a vaccine against SARS-CoV-2 that is suitable for many people will be available on the market.

If a vaccine is approved, mass production will be another challenge. Gene-based RNA vaccines, which can be produced relatively quickly, would have an advantage here.

Pharmaceutical companies that are specialized in the production of vaccines, such as the Serum Institute of India, are already preparing larger capacities, even though they do not yet know which active substance they will eventually produce. 

When does herd immunity occur?

It is true that more and more people are becoming infected worldwide. By the end of June, a good 10 million people had contracted the virus. However, with its population of 7.8 billion, the world is still a long way from achieving any effective degree of immunity  to the disease.

In addition, it is unclear whether recovered patients remain permanently immune to the virus. A serological blood test  can determine whether someone is carrying antibodies against the virus. A PCR test taken with a cotton swab can make it clear whether someone is acutely ill and contagious. 

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