A year and a half since Covid-19 was first registered in the Chinese city of Wuhan, the question of how the virus appeared is still a mystery.
Since the beginning of the pandemic, scientists in several countries have also determined whether the corona virus survives in water and how dangerous it is.
In the sea of reports and analyzes that had the same goal - find out how the virus is transmitted and how to prevent its further spread - the presence of molecules of this virus in wastewater was confirmed.
In the small Belgrade settlement of Višnjica, on the left bank of the Danube, where there are three waste water outlets, researchers also registered the RNA (genetic material) of the corona virus.
Research by the "Siniša Stanković" Institute for Biological Research (IBISS) in Belgrade, which was conducted in cooperation with partners from Hungary, Austria and the Netherlands, indicates, however, that there is no danger for now.
The population of Belgrade can come into contact with untreated water, because the discharge points are often not secured in terms of limited access, says Stoimir Kolarević, senior scientific researcher of the Institute and one of the research participants.
For now, there is no fear of infection, adds Kolarević for the BBC in Serbian.
- WHO: It is unlikely that the corona virus originated in a Chinese laboratory
- A message from the laboratory in Wuhan: We have nothing to hide
- Corona virus: American study that casts doubt on the official start of the pandemic
The SARS-CoV-2 virus was first discovered in China at the end of 2019, and by June 2021, it had spread throughout the world, leading to more than 180 million confirmed cases of infection and close to four million deaths.
Where does the corona virus come from in rivers and can we get infected that way?
Waste water are natural waters whose chemical, biological and physical characteristics change due to specific use.
They are a mixture of water and waste from apartments, public buildings, public areas and industry.
Cause of content of toxic substances they are harmful to the environment but can also endanger human health.
Through the excrement of persons suffering from Kovid-19 with symptomatic or asymptomatic infection, but also through other bodily secretions, the corona virus can be excreted from the body and reach waste water through the sewage network.
In this case, to the Danube, which together with the Sava has about 100 sewage outlets.
Can the population become infected if they come into contact with untreated water containing the corona virus?
"The infectivity of the corona virus in waste water is extremely low and so far there are no recorded cases of Covid-19.
"Research shows that there is no danger.
"In wastewater, it is not the virus in an infectious form, but parts of the virus, i.e. RNA molecules," explains Stoimir Kolarević.
Tamaš Petrović, scientific advisor of the Scientific Institute of Veterinary Medicine "Novi Sad", states that the finding of this, as well as other human or animal viruses in waste water and surface water certainly represents a risk for the health of people and animals, but the question is how much of a risk it is. .
"It is known from the literature that some researchers confirmed that the SARS-CoV-2 virus they found in waste (sewage) water is infectious, i.e. they managed to isolate it on cell culture, therefore there is a possibility of infection of people who come into contact with these waters quite realistic."
So why are these studies important?
The presence of the virus in the population could be recognized before the first clinical cases, because the RNA of the corona virus can be detected in human excrement several days before the onset of symptoms.
This would provide an opportunity to act preventively before the situation escalates, Kolarević points out.
"The system would enable the early isolation of certain cities or municipalities, which would prevent a complete lockdown."
Predictions about the course of the epidemic can be made for a shorter next period, similar to the frequency of newly infected people based on clinical data, he notes.
Tamaš Petrović also believes that such research can help in further monitoring the number of people infected with Covid-19.
In addition to the preventive role, monitoring of waste water can also indicate whether the epidemic is waning or the number of infected is increasing.
"Such monitoring has proven to be very useful and fully reflects the speed of the spread of the virus, i.e. the increase or decrease in the number of infected people, i.e. that such monitoring is sensitive enough to be able to provide an answer in real time to the question of whether the spread of the virus in the population is increasing, stagnating or decreasing ".
Research can help in the discovery of new strains, which appear every day due to the mutation of the genetic material of the virus.
It is these mutations that contribute to the virus staying longer in the population.
"By identifying the molecules of corona strains that are registered in wastewater, all changes in the virus that circulates among people can be determined very efficiently and accurately.
"The entry and presence of new virus strains can be determined, and these are very important epidemiological data," believes Petrović.
- Corona virus: What are the symptoms and what does it do to the body
- Alpha, Beta, Gamma - the new strains of the corona virus will be named after Greek letters
- Delta strain of corona virus - what are the symptoms
How does the aquatic environment affect the corona virus?
He explains that SARS-CoV-2 is not one of the extremely resistant viruses in the external environment, so it is always a question after what time and depending on the environmental conditions, it is no longer contagious.
"Such research is being conducted and will certainly answer this question."
When it comes to the RNA of the virus, Stoimir Kolarević emphasizes that it is impossible to say with precision, bearing in mind that the quality of waste water varies.
"According to some research, RNA in wastewater breaks down in less than 24 hours.
"Research for surface water is still ongoing."
The RNA concentration also depends on the number of active cases in the population, on the size of the sewage network in terms of the number of inhabitants connected to it, but also on the type of sewage - whether it is exclusively for fecal water or receives street sewage as well.
Temperatures and precipitation are factors that also affect RNA.
"It decomposes more slowly at a low temperature.
"Rain can significantly reduce the amount of viruses in waste water, if we are talking about sewage, for example, which also serves for street drainage," adds Kolarević.
Lack of purification system
The majority of the population of Serbia has no built-up area waste water treatment systems.
Only eight percent of municipal water is purified before discharge, it was stated in Naled's analysis.
Among existing systems, the largest number use technologies that are three decades old.
The problem is further aggravated by the lack of sewage networks.
About 65 percent of the population is connected, but it is mostly in urban areas, while the rest of the households use septic tanks, which is the most common case in rural areas.
The number of inspectors at the local level is also insufficient.
Currently, six inspectors are dealing with this problem, according to the analysis of the National Alliance for Local Economic Development from the beginning of this year.
There is progress, but not enough.
The consequences of an insufficient water purification system are manifold.
Toxic substances found in water and sludge have a negative impact on the environment and human health.
Many water supply systems are linked to the use of river water and groundwater or alluvial river plains.
Their pollution puts the quality of the water we drink into question, which is a growing problem in Serbia, especially in Vojvodina.
Any pollution of the river changes the chemical regime, which directly affects the entire ecosystem, and this further leads to the extinction of certain plant and animal species.
The consequences are also felt in agriculture.
Every use of polluted water for irrigation directly affects humans.
- Why the waters of Serbia are polluted and how to protect them
- Drina pollution - visible from space
- What are the biggest environmental problems of the Balkans?
The biggest wastewater problem in Belgrade
The same analysis shows that the region of Belgrade leads in terms of the burden of waste water, household water, processing industry and the number of septic tanks, while the Toplička region is on the opposite pole.
In Belgrade, there are about 100 sewage outlets into the Sava and Danube.
"190 million cubic meters of waste water is poured into the Sava and Danube, which can be compared to 60.000 Olympic swimming pools or 19 million cisterns", Minister Zorana Mihajlović said in January 2020, announcing the construction of a wastewater treatment system in cooperation with Chinese partners.
The biggest problem is the waste water factory in Veliki Selo - it covers one and a half million people living in the territory of Belgrade.
The Government of Serbia signed a contract based on the agreement reached by the presidents of Serbia and China, which begins the construction of the first factory for the processing of waste water in the capital.
The value of that project in the first phase alone is 285 million euros, while the second will cost between 400 and 500 million euros.
With the construction of the factory, 80 percent of direct discharges of sewage into rivers will be solved, he said energjiportal.rs.
Viruses in wastewater can make people sick
The consequence of the low level of waste water collection and purification is the high content of potentially toxic elements, both according to the level of the maximum allowed concentration and the frequency of its occurrence.
There is a risk to human health in that case.
"It is generally known that the most common viral microorganisms that can be found in surface water (rivers, lakes, streams), in water intended for recreational activities (swimming pool), for irrigation, are human adenovirus and norovirus (and there are many others: poliovirus, hepatitis A, hepatitis E, enteroviruses, rotaviruses...) and both have been found to cause and cause human disease.
"These infections are even often referred to in world literature as waterborn viruses, i.e. infections," Tamas Petrović points out.
How is the world?
That sewage water is an important tool for early detection of Kovid-19, he confirmed National Institute of Health in Italy.
In the study, scientists at the institute examined 40 sewage samples collected from wastewater treatment plants in northern Italy between October 2019 and February 2020.
The findings indicate that water from Milan and Turin contained traces of genetic viruses in December, while wastewater from Bologna started showing traces of the virus a month later.
The first case in Italy was officially recorded in February.
However, Giuseppe La Rosa from the institute notes that the research "does not automatically imply that the main transmission chains that led to the development of the epidemic in this country originate from these first cases".
A similar study was also conducted in Spain, the country that during 2020, after Italy, was the most affected by the corona virus in Europe.
It shows traces of the virus in wastewater collected in mid-January in Barcelona, which is about a month and a half before the first local case.
As early as April 2020, research teams in the Netherlands, Sweden and the United States of America they found traces of the corona virus in waste water.
The South African Medical Research Council team in June 2020 last year also detected SARS-CoV-2 in wastewater at five treatment plants.
He expanded the testing to 19 more facilities in order to work out the logistics for further monitoring of the pandemic.
In March of this year, the European Commission issued a recommendation on monitoring the presence of corona in wastewater.
Supervision should be introduced by all EU member states by October this year, in all cities with more than 150.000 inhabitants.
Watch the video about the famous Zemunc and the lover of the Danube
European Danube Day
The Danube is of great importance for Europe. It flows through ten countries and is the most important transport corridor.
It originates in Germany near the city of Donauschingen and flows into the Black Sea.
It originates from two smaller rivers - Breg and Brigah.
It is 2.857 kilometers long and is the second longest river in Europe, after the Volga.
It flows through 10 countries (Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova and Ukraine), and as many as four capitals are located on the banks of the Danube (Vienna, Bratislava, Budapest and Belgrade).
The length of the Danube, which flows through Serbia, is 587 kilometers.
Some of the biggest tributaries of the Danube are Tisa, Morava, In, Vah, Drava, Sava, Olt and Prut.
The international convention on the protection of the Danube River was signed by the Danube countries and the European Union on June 29, 1994 in Sofia, and that day is celebrated as International Danube Day.
It is celebrated in 14 European Danube countries that are signatories to the convention, including Serbia.
The Danube is the river with the most different names.
In Germany and Austria it is called Danau, Hungarians call it Duna, in Turkey it is Tipa, while in France it is known as Le Danub.
As one of the most important European rivers, it contains many protected species of flora and fauna.
In Serbia, you can find catfish, one of the protected species of fish.
Many warships were sunk during World War II to the bottom of this river.
When the level of the Danube drops, the wrecks can be seen from the shore.
Austrian composer Johann Strauss composed one of the most beautiful compositions "On the beautiful blue Danube".
Follow us on Facebook i Twitter. If you have a topic proposal for us, contact us at bbcnasrpskom@bbc.co.uk
Bonus video:
