The COVID-19 pandemic continues, and specialists warn of further threats. Mild winters and longer summers are conducive to the emergence of species of mosquitoes in Europe that transmit infectious diseases that do not usually occur in our country, says Dr. Aneta Afelt from the Espace-DEV Institut de Recherche pour le Développement in France. The specialist also works at the Interdisciplinary Center for Mathematical and Computational Modeling at the University of Warsaw, and is a member of the COVID-19 Team at the President of the Polish Academy of Sciences.
- Dr. Afelt points out that the snowstorm in Warsaw on Monday, January 17, confirms that in winter air temperatures in Poland increasingly oscillate around 0 degrees Celsius.
- As he explains, mild winters and longer summers favor the vegetation of mosquitoes in Europe that carry infectious diseases
- – And for blood-sucking mosquitoes, both animals and humans can be hosts. So, if a mosquito becomes infected after a bite of a sick animal, and then bites a human, there is a possibility of transmitting the infection to humans, Afelt explains.
- He also points out that the SARS-CoV-2 epidemic is not a direct result of climate change, but is related to “the rapid, even destructive entry of humans into the natural environment and the shortening of the distance between humans and wild animals”
- The expert also indicates what may be the source of further infections and epidemics
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PAP: On the initiative of the National Climate Change Center, an international report “The relationship between climate change and infectious diseases” was prepared. Where did the idea of such a development come from, now, since the COVID-19 pandemic is unlikely to be related to climate change? There is only no doubt that the winters are more and more often mild.
Dr Aneta Afelt: This research project was not related to a pandemic – it started before it happened. Research linking climate change with changes in the natural environment has been conducted for at least 20 years. It is obvious that along with the change of climatic conditions, the delicate ecosystem balance changes and, as a consequence, various species of plants, animals and insects “migrate” – that is, organisms follow optimal environmental conditions for their requirements.
How?
Dr. AA: Change in air temperature and humidity, as well as rainfall intensity, and with it – a general change in climatic stability, e.g. the already observed process of extending the growing season affects the environmental conditions of the existence of microorganisms and the movement of various types of pathogens. This applies to pathogens of common plants, as well as animals and humans, as well as those that constantly circulate between animals and humans.
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The SARS-CoV-2 coronavirus could jump from animals to humans, but is it possible to predict the risk of further pathogens?
Dr. AA: Before the era of mass air and sea transportation, the movement of insects and animals between different geographic areas was very limited and stretched over time. This has happened frequently in the past, but so far it has been a long process. For example, the transfer of the plague from the border of Mongolia and China to Iran and Europe took 200 years as a consequence of a trade route. Currently, the movement of animals, and in particular the accidental movement of insects, and with them – diseases – is significantly shortened. An example is the mosquitoes originating in Equatorial Africa, displaced to South America, Asia, and currently colonizing southern Europe.
Is it the same for Asia?
Dr. AA: In epidemiology, mosquitoes are a vector or mediator between animals and humans in diseases such as malaria, Japanese encephalitis, dengue fever, and chikungunya. The research we conducted in Vietnam with specialists from France, the USA and Vietnam showed that, for example, tiger mosquitoes caught in four provinces of Vietnam were closely related to mosquitoes in Southeast Asia and Australia, but also, unfortunately, to individuals of the same species in Romania! This “family” affinity is achieved by comparing mosquito genetic profiles.
Such mosquitoes may soon appear even in northern Europe?
Dr. AA: It is primarily humans that distribute mosquitoes (as larvae or eggs). And when they are moved to ecosystem niches where they have the conditions to reproduce, they can acquire a new location. Climate change helps in this – extending the period of temperature favorable to the insect reproductive cycle, ie at least nine days with an average temperature not lower than 19 degrees Celsius. During this time, there may be a transition from the egg to the larva. The larval period is also the spore period. Therefore, if there is no too harsh winter and its duration is shortened, and at the same time summer is lengthening, then the climatic conditions are favorable for the full reproductive cycle of such a mosquito, i.e. the transition from the larva to the adult specimen.
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However, mosquitoes alone, which can carry different species of pathogens, are not enough to spread infectious diseases.
Dr. AA: It is enough, however, for animals that are migratory species, such as birds, to appear in the same niche in the ecosystem. And for blood-sucking mosquitoes, both animals and humans can be hosts. So, if a mosquito becomes infected after being bitten by a sick animal, and then bites a person, there is a possibility of transmitting the infection to humans. If these are only isolated cases, the risk of spreading the disease is low. However, if there are more of these mosquitoes in ecosystem niches, the risk of developing infections in geographic conditions and places where they have not been present before also increases.
Even at the beginning of the XNUMXth century, malaria was present in Europe, even in Poland and Germany, but it was successfully eradicated. The report “The link between climate change and infectious diseases” points out that there are still mosquitoes with the potential to cause malaria in Germany, although fortunately it is not endemic. Malaria parasites are brought only by tourists, including Poland.
Dr. AA: Malaria vector mosquitoes are already in southern Europe and endemic or local infections are becoming increasingly common.
Can they also appear in Poland?
Dr. AA: Not immediately, but in the long run, there is such a risk – especially when there is a favorable change in climatic conditions. We are already seeing a shift in parasitic diseases, so far mainly among wild and domestic animals. Dogs begin to get sick with parasitic diseases that until recently did not occur in our climate zone. Climate change, however, causes the shift of optimal conditions within an ecosystem niche, beneficial e.g. for insects, which are vectors for previously unknown diseases, and for some parasites.
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We can also expect other tropical diseases, such as dengue fever – a variant of hemorrhagic fever, chikungunya viral disease or West Nile fever?
Dr. AA: Yes, as long as we have intermediary organisms. In the report, we remind you that dengue fever was already present in southern Europe and in 1928 about 650 people fell ill with it. the inhabitants of Athens and Piraeus. Currently, the climate in Central Europe is unfavorable to the virus that causes it, but rising temperatures and greater population mobility may change that. A. albopictus mosquitoes, which carry chikungunya disease, are already present in the southern and central European Union and are still spreading. In turn, about 1996 people near Bucharest were infected with West Nile fever in 1997-400.
The report also warns against Vibrio bacteria in the Baltic Sea; they can cause gastroenteritis as well as wound infections and sepsis. In 2018, there were as many as 107 days on the Baltic coast suitable for the development of Vibrio.
Dr. AA: If the average air temperature in a given region increases, so does surface water warming. Therefore, when we have several or several days with very high air temperature, the water temperature rises. In such water, bacteria and viruses more adapted to warmer conditions may appear. And vice versa – we observe a significant disturbance of water glaciation in winter. In Central Poland, air temperatures more and more often – as this year – in winter oscillate around 0 degrees Celsius, the forecasts of climate change suggest that at the end of the 17st century our winter will be snowless – it will be too warm to maintain the snow cover. The snowstorm in Warsaw on Monday, January XNUMXth is an excellent example: in the middle of winter we had hail, heavy snowfall and… lightning discharges, so far typical of the spring and summer period. A few hours later, the snow melted.
The appearance of the COVID-19 pandemic was accidental, but to what extent is it related to climate change?
Dr. A.A. The first stage took place in natural conditions, at least so far everything seems to indicate it. Here, the risk factor was not climate change, but the aggressive transformation of the natural environment and the shortening of the distance between wild animals, domestic animals and humans. The published results of genetic studies on the structure of the SARS-CoV-2 virus do not so far indicate that the concept of the laboratory phase in virus evolution is correct.
The point is, haven’t humans tinkered with the DNA of this pathogen?
Dr. AA: I am not a specialist in this field, but if this virus had a laboratory stage in its evolutionary cycle, it would show up in its genetic makeup as a “reproductive break”, or stability in the genetic makeup of the virus. And of course, we do not have such proof yet. Regardless, there is no doubt that it is a virus of zoonotic origin, derived from nature.
Does the research confirm it?
Dr. AA: In 2014-2018, I participated in research in Southeast Asia, Cambodia and Los, during which bats were caught and genetic analyzes of pathogens detected in them were carried out. Those who were carriers of coronaviruses moved closer to humans in their life activities. Usually people change the environment in such a way that it favors the proximity of bats of different species that do not come into contact with each other in natural conditions. For example, the development of electricity attracts insects, which are food for bats – therefore insectivorous bats adapt to the living conditions in the vicinity of people. Fruit bats, on the other hand, roam the fruit orchards. The process of bats transfer to socio-ecosystems is epidemiologically dangerous. But that doesn’t mean bats are dangerous. It is our management of natural environment resources that is far from sufficient and not adjusted to non-obvious threats.
Did this research detect SARS-CoV-2 related coronavirus?
Dr. AA: No, our project did not show the presence of the coronaviruses, which are the direct relatives of SARS-CoV-2 – and therefore the one that colonized the population in Wuhan, China. However, in January 2019 a search of the zoonotic coronavirus database began. My colleagues with whom I conducted research in Cambodia and Laos, in 2020, published the results of analyzes from these countries and it turned out that a coronavirus was circulating locally among bats, very closely related to that from Wuhan. Thus, in the region of Southeast Asia, as a result of natural evolution, there were conditions for such colonization attempts. It was a natural and long process of matching the virus to the next host.
Until a person or group of people was attacked in which SARS-CoV-2 could have multiplied and then spread?
Dr. AA: We all experience in our lifetime attempts to colonize our body with all kinds of bacteria, viruses, and parasites. However, only some of them are successful, the vast majority fail.
Wasn’t it related to climate change?
Dr. AA: No. It was rather related to the quick, even robbery entry of man into the natural environment and the shortening of the distance between man and wild animals.
So what was most conducive to rapid human colonization by SARS-CoV-2?
Dr. AA: As early as six months after the outbreak in China, this coronavirus was present in every country. The main reason for this was transportation, as it usually took five or six days between infection and the onset of symptoms. During this time, it was possible to travel a long distance and transfer the infection to any corner of the world.
What other infections may still threaten us?
Dr. AA: The World Health Organization (WHO) lists ten such threats, coronaviruses were high on this list from the start. An article from our research warning against these pathogens was published in 2018, and an epidemic in Wuhan appeared in the fall of 2019. This was no surprise to us.
And what new insects can be vectors of infectious diseases?
Dr. AA: A Chinese-origin Asian hornet (Vespa velutina) appeared in Europe, brought to Europe around 2004, possibly with the shipment of porcelain. He has found himself well in Western Europe, is already present in France, Italy and Germany – and is getting closer to Poland. Undeterred, it does no harm to people, but it becomes the dominant insect in the niches of the ecosystems where it appears, and thus reduces the insect biodiversity typical of the European ecosystem. Our European ladybirds – so well known in Poland from our childhood, are also replaced / displaced by insects from Asia.
Author: Zbigniew Wojtasiński
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