Scientists have been warning for years that the careless progress of civilization will lead the world to a catastrophe. The devastation caused by the SARS CoV-2 virus may give the impression that this prophecy is already fulfilled, but “on standby” await microbes as dangerous as the coronavirus, for which there is no effective cure or vaccine. Worse, they can trigger further pandemics. Why should you be afraid of them and what can you do to limit their spread?
- Already in 2018, WHO developed a list of infectious diseases that can become epidemics
- – It can be said that man has prepared this fate for himself. The growing population and density is a great opportunity for viruses to move smoothly – explains Prof. Agnieszka Szuster-Ciesielska, virologist
- Experts agree that the greatest threat, and perhaps the next pandemic, is zoonotic viruses
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To blame for the epidemic
Wybuch pandemii koronawirusa zaskoczył cały świat. Być może jednak nie powinien. The World Health Organization (WHO) already in 2018 compiled a list of infectious diseases that pose the greatest threat to public health due to their epidemic potential and lack of countermeasures. Significantly, among them was the unidentified “disease X”, which experts described as devastating the respiratory system, spreading rapidly and most likely a type of pandemic flu. COVID-19, which fits this description perfectly, took over all continents less than a year after the ranking was announced.
The WHO project aimed not only to draw attention to the lurking danger, but also to stimulate the world of science to react: transferring resources (financial, human and time) to researching these specific pathogens in order to develop methods of efficient diagnostics, effective treatment and, above all, effective prophylaxis in the form of preventive vaccinations. Theoretically, it was not a difficult task, because most of the dangerous infectious diseases that are talked about in virological circles have been known for years and occur in animals. Practically, this is a huge challenge, because when transferred to humans, they often change beyond recognition, becoming much more aggressive and deadly.
How is it possible that these microorganisms, mainly viruses, because they are characterized by the greatest virulence, are even transmitted to humans? While in farm animals, through close contact with the breeder, we do notice a certain danger, such exotic creatures as fruit bats or dromedary camels seem to be a distant threat. Meanwhile, the changes that man makes in the fauna world make the danger not only real, but also very close. According to conservative scientists’ estimates, we will soon be much more exposed to the effects of microbes unknown or not known to humans today. Dlaczego?
– It can be said that man has prepared this fate for himself. The growing population and density is a great opportunity for viruses to efficiently move among susceptible individuals – explains Prof. Agnieszka Szuster-Ciesielska from the Department of Virology and Immunology at the Maria Curie-Skłodowska University in Lublin.
As the virologist points out, South Asia is the most significant in this regard. It is largely influenced by the large population and close human contact with farm animals, such as pigs or poultry, but also well-established folk medicine and culinary tastes.
– In many Chinese city markets you can get virtually all, even exotic animals – bats, snakes, lizards, peacocks, young dogs and wolves, pangolins and even koala bears. Their catching and direct contact may result in “leaking” of subsequent viruses onto humans. And if these new viruses adapt to their new host as efficiently as SARS-CoV-2, then another pandemic lies ahead. – he adds.
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In the animal world
A good example of such a pathogen is the SARS virus, which was not found in humans before 2002. Like its “successor” – SARS CoV-2 – it causes flu-like symptoms, so recognizing it is not an easy task.
The disease first appeared in China and Vietnam, but due to the information blockade, news about the threat did not cross the state border until several weeks later, in February 2003. For this reason, the SARS virus began to spread quickly, and the medical services of the countries to which they traveled infected in Asia, it took a long time to identify the pathogen and establish its transmission pathway. Although scientists have known the coronavirus for almost two decades, to date, they have failed to develop an effective vaccine for SARS, and the disease caused by the pathogen is treated only symptomatically.
The list of diseases with high epidemic potential also includes another disease caused by a pathogen from the coronavirus family – MERS. Like SARS and COVID-19, it causes symptoms similar to common respiratory diseases: fever, chills, fatigue, muscle pain, cough. Contact with an infected animal is dangerous for humans, also in the form of eating its meat. Although there is no evidence that the disease is transmitted by airborne droplets, close contact with someone with MERS may contribute to the disease. Middle East Respiratory Syndrome was first identified in 2012 in Saudi Arabia, with more cases later emerging in the Middle East. Three years later, an outbreak of MERS was diagnosed in South Korea, where the disease became a major problem in healthcare facilities.
What these two coronaviruses have in common is that animals were their reservoirs (it is estimated that up to 60% of newly emerging viruses come from them), in the case of MERS – dromedary camels, and SARS – bats. Their contact with people seems to be negligible, but these are only appearances. Mass cutting of trees and gradual deforestation of the Earth is an interference with the natural environment of many animals. As a consequence, they either look for a new place to live, or live in an old, though completely changed one, which includes, for example, a new housing estate or a complex of office buildings – all “inhabited” by people. Nocturnal animals, which are the most common natural hosts of viruses, are especially dangerous here.
– These very old mammals carry ancient viruses with universal replication mechanisms, which also work well in humans. In the past few years alone, more than 200 new species of coronavirus have been detected in bats. Some of them, in laboratory conditions, are able to infect human cells, which proves their great epidemic potential – confirms prof. Agnieszka Szuster-Ciesielska.
Handwings are also vectors for two other viruses that scientists describe as particularly dangerous. It’s the Nipah and Hendra paramyxoviruses (HeV)which attack primarily the nervous system (the first one can even lead to inflammation of the brain) and the respiratory system. The first epidemics of diseases caused by these pathogens date back to the 90s, but these viruses still cause disease – both in humans and animals (during the epidemic in Brisbane, Australia, HeV was diagnosed in horses). It is precisely the bats, whose range extends from Australia, through India, to China.
– These are highly lethal viruses, classified – next to the Ebola and Marburg hemorrhagic fever viruses – among the safety level IV pathogens. The only good news is that these viruses have not acquired the ability to spread from person to person – all known cases of infection today are zoonoses, the virologist points out.
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Prophylaxis of humility
Haemorrhagic fever is another group of acute infectious diseases that, according to experts from the World Health Organization, requires extensive analysis in terms of developing effective prophylaxis and therapy. Although it consists of a number of diseases of different etiology and course, the diseases are linked by a high fever, which can even lead to bleeding, haemorrhage and blood clotting disorders. These diseases are classified as zoonoses, because their reservoirs are primarily animals, including rodents, bats and monkeys. Unfortunately, the viruses that cause them are easily transmitted by mosquitoes and ticks, which plague systematically most countries of the world.
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The most famous type of hemorrhagic fever is that caused by infection with the Ebola virus. The pathogen was first identified in 1976 in Zaire, and the largest Ebola epidemic by range occurred in West Africa in 2014-2016. Large outbreaks then emerged in Guinea, Liberia and Sierra Leone, but the virus also reached North America and Europe. In total, over 28,6 thousand cases of infections were detected, of which nearly 12 thousand were it was fatal.
Less than two years later, Ebola also seriously affected the Democratic Republic of Congo. The epidemic was tragic – although there were fewer cases than a few years earlier in other African countries (3470 reported cases), the death rate was as high as 66%. Almost one in three of the 2287 victims of Ebola in the DRC are children. The country has fought the deadly virus for the tenth time, a fight that was only ended last year, luckily, with the development of an effective vaccine. Other hemorrhagic fevers are still “waiting” for such a remedy: Marburg, Lasso, the Rift Valley and the Crimean Congo.
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Insects as popular vectors are also responsible for infections with viruses considered to be typically exotic until recently: dengue and zika, as well as yellow fever, although the latter disease can already be vaccinated. All three are very dangerous.
Dengue – manifested primarily by fever, headaches, muscle and joint pains, and a characteristic rash – can take the form of a haemorrhagic form in its most severe form. Mortality then reaches up to 30 percent. It is a disease that has been known for a long time (its descriptions can be found in 50th-century documents), but its greatest outbreak took place after World War II. Over the decades, dengue has taken a deadly toll (100-100 million infections per year) in many regions of the world – it is estimated that the virus is endemic in over XNUMX countries.
The zika virus, in turn, is most often asymptomatic, but it is especially dangerous for pregnant women bitten by a mosquito carrying the pathogen. The virus can cause microcephaly in a child. Zika is not as widespread as dengue fever, but it crosses borders every year. Originally known only in Africa, today it can also be found in Asia, America and Europe. As prof. Agnieszka Szuster-Ciesielska is the result of climate change, in particular global warming.
– Only in the last 150 years, the average temperature has increased by almost 0,8 degrees Celsius in the world and by about 1 degrees Celsius in Europe. It is estimated that by 2100 the global temperature may increase by another 1,8-4,0 degrees C. This causes, already visible today, the shift of climatic zones, and thus a change in the range of occurrence of animals, including insects. .
The year 2100 for us today may seem distant, and the changes taking place in nature, which scientists pay attention to, are exaggerated, but the danger is closer than we think. The rapid and extensive transmission of the COVID-19 coronavirus is a prime example of this. Whether and which pathogen will follow in its footsteps and manage to trigger another global crisis depends largely on our long-term actions and our humble attitude towards the force of nature.
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