Health : Why do we catch diseases from animals
We are increasingly concerned about the dangerous new virus that is causing the epidemic in China. The number of people sick or dead from viral pneumonia caused by coronavirus transmission is increasing rapidly, despite the quarantine of thousands of people and other measures taken to try to stop the virus. Coronavirus transmission in other countries is through travelers including France. Fear of a possible global impact affects the economy, tourism and business.
We still know very little about the coronavirus which is currently scientifically named 2019 nCoV, which means the veut new coronavirus ’. Scientists and doctors are looking for more. Among the key questions regarding the virus is the issue of coronavirus transmission and why there are people who are infected but do not develop symptoms.
Coronavirus transmission has occurred from wildlife to humans
The new coronavirus that is said to come from wildlife highlights our risk of catching animal diseases. It is likely to become more problematic in the future, as climate change and globalization are changing the way animals and humans interact.
How can animals transmit diseases to us?
Over the past fifty years, a multitude of infectious diseases have spread rapidly after making the evolutionary leap from animals to humans. The AIDS crisis of the 1980s had its origin among the great apes. Between 2004-2007, the avian flu pandemic came from birds and sleeping in it gave us the swine flu pandemic in 2009. More recently, it was discovered that severe acute respiratory syndrome (Sars) was caused by bats mice from civets and bats also gave us Ebola.
Humans have always caught animal diseases. In reality, most new infectious diseases come from wildlife. But environmental change is also speeding up this process, as increased city life and international travel mean that when these diseases appear, they can spread faster.
How is it that animals are the source of coronavirus transmission?
How can diseases jump between different species?
Most animals carry a range of pathogens: bacteria and viruses that can cause disease. The evolutionary survival of pathogens depends on the infection of new hosts and jumping between species is a very effective way to continue to survive.
The new host's immune system is trying to kill the pathogens, which means the two are caught in an eternal evolutionary game trying to find new ways to defeat themselves. For example, about 10 percent of those infected died during the SARS epidemic in 2003, compared to about 0.1 percent who died from the "normal" flu epidemic.
Bats can also transmit disease to humans
Climate and environmental change are removing and alternating the habitat of animals which changes how they survive, where they survive and what they eat. The way men live has also changed: 55 percent of the global population now lives in cities, an increase of 35 percent in the past 50 years.
Large cities provide new living spaces for animals: rats, mice, raccoons, squirrels, foxes, birds, jackals, monkeys can now live in rural parks and gardens thanks to garbage left there by men. Often, species of fauna manage to survive better in cities than in nature thanks to potential food supplies which transforms urban spaces in a melting pot for the evolution of diseases.
Pangolins are likely sources of new virus, scientists say
Exactly what animal does this coronavirus come from?
Coronaviruses are common in many species of animals, including camels and bats. Rarely these coronaviruses can evolve and infect men and then spread between men. Recent examples of this include the SARS-CoV virus and the MERS-CoV virus.
Most coronaviruses infect animals, but not humans. In the future, one or more can potentially evolve and spread to humans, as has happened in the past. We are not yet able to understand why certain coronaviruses can infect humans.
The market where coronavirus transmission started
Scientists in Gangzhou, China have suggested that the pangolin, an ant-eating long-nosed mammal that is often used in Chinese medicine, is the likely animal source of the coronavirus, which has already infected more than 30,000 people.
Scientists are speaking for the moment only for a suggestion, based on a genetic analysis but which seems rather plausible. This is a very interesting observation and there are now other facts that prove that pangolins carry viruses related to the 2019-nCoV coronavirus.
The University of Agriculture in Guangzhou in South China announces that two of its scientific researchers Shen Yongvi and Xiao Lihua have identified pangolin as the potential source of the coronavirus nCoV-2019 based on a genetic comparison of the coronavirus taken from the animal and humans infected with the epidemic. The sequences are 99 percent similar, the scientists said.
Here is the pangolin which has been identified as the potential source of the new virus
Before, researchers had already noticed that coronavirus is a possible cause of death in pangolins and that the nCoV-2029 virus and coronaviruses in pangolins use receptors with a molecular structure to infect cells.
Even before the official announcement, pangolins were good candidates to be middlemen for the virus, so it is very interesting that the researchers found such a close sequence.
Pangolins are protected animals, but illegal traffic is widespread and some species are endangered. Pangolins are sold, controversial for their meat and scales and for their use in Chinese medicine in which parts of these animals are used to treat skin diseases, menstrual disorders and arthritis. Chinese law says that people who sell pangolins can be punished with up to 10 years in prison.
What are the measures to take against coronavirus?
This type of coronavirus appeared in the Chinese city Wuhan in December 2019 and is believed to have infected humans at a seafood and wildlife market, where many of the first infected worked. The pangolins were not on the list of goods at the market, but an illegal sale may explain this case. Scientists in Beijing claimed the snakes as sources of the coronavirus last month, but the theory was rejected by other scientists.
Is the new coronavirus comparable to the SARS virus or the seasonal flu?
The new coronavirus transmission is genetically close to the SARS virus of 2003 and appears to have similar characteristics even if what is currently known about the virus is still quite limited.
The SARS virus appeared in 2002 in China and more than 8000 cases have been registered in more than 33 countries for an eight-month period. At the time, one in ten people who were sick died from the virus. The 2019 new coronavirus outbreak triggered around 10,000 cases in China in the first month of the epidemic, with additional cases in Europe and other countries. Cases and deaths of the virus continue to increase. At this point, there is very little information to say for sure how deadly the new virus is, but preliminary information indicates that the new virus is less fatal than SARS.
While coronavirus and influenza viruses do not spread from person to person and cause similar symptoms, the two types of virus are very different and do not behave in the same way. It is still very early to draw conclusions about how the new coronavirus spreads, but preliminary information indicates that the coronavirus is transmitted in the same way as SARS and some other influenza viruses. The World Health Organization estimates that each year around 40,000 people in the European Union, the United Kingdom, Norway, Iceland and Liechtenstein die from causes associated with influenza viruses.
How dangerous is the new coronavirus?
It appears that the new coronavirus is less severe than SARS, which killed around 10 percent of those infected in 2003. At the moment, 2 percent of those infected with the coronavirus are dead, according to the most recent information. Many of the people who died are elderly or have health problems such as diabetes. But coronavirus transmission is easier than that of SARS, scientists say.
How is coronavirus transmitted?
Coronavirus transmission may not occur through coughing, sneezing, or other contact with infected saliva. There is no evidence of aerosol or airborne transmission. The MERS and SARS viruses were generally spread by respiratory droplets produced by coughing or sneezing by someone sick. These two viruses were generally transmitted through close contact.
Can masks protect us?
Scientists and mask makers say that only a properly used reusable N95 mask can both protect us from contacting the virus and at the same time prevent us from infecting others if we are sick. Masks made of polyurethane foam or paper do not filter out the small particles that are responsible for coronavirus transmission.
Should we be worried?
It is still very early to say how severe the diseases caused by this new coronavirus are. It is possible that many people become infected but do not get severely ill. We are still trying to determine the exact number of people infected. In addition, the new virus can mutate and become more virulent when it spreads among populations.
Who is most at risk?
New diseases in new hosts are often more dangerous and that is why this new coronavirus is so worrying. Certain groups of the population are more vulnerable to catching the virus than others. The poorest city dwellers who work in the cleaning and sanitation arena have of course a better chance of catching and spreading the virus. It is also possible that these people have a weaker immune system because of their poorer nutrition and their exposure to worse and less healthy conditions. And if these people get sick, they can rarely afford medical care.
Coronavirus transmission can also occur more quickly in large cities since the concentration of people who breathe the same area and touch the same surfaces is greater. In some cultures, people also use urban wildlife for food by eating animals caught in the city or bushmeat harvested nearby.
What can we do ?
Societies and governments are trying to treat each new infectious disease as an independent crisis, instead of recognizing that all of these diseases are symptoms of the changing world. The more we change the environment, the more opportunities there are to disrupt the ecosystem and create opportunities for the emergence of new diseases.
Only about 10 percent of the world's pathogens have been documented, so we need more resources to identify the rest and also who the animals are that transmit them. For example, how many rats are there in London and what are the diseases transmitted by these rats? Many city dwellers enjoy city life, but we must also recognize that some animals carry potential dangers.
It is important to keep track of animals that have just arrived in cities and if people kill or eat wildlife or if people bring them to local markets to sell them. Trying to improve the situation, treating waste and controlling animals are the ways to stop the emergence of new diseases. A change in environmental management is strongly recommended.
Pandemics are part of the future
Recognizing that new diseases are emerging and spreading puts us in a strong position to fight the new pandemics that are an inevitable part of the future. A century ago, the Spanish flu infected around half a billion people and killed between 50 and 100 million people worldwide. Scientific advances and large investments in public health guarantee that such a pandemic will be better controlled in the future.
Yet the risk remains real and potentially catastrophic and if something similar happens again, it will reframe the whole world. In the middle of the last century, some claimed that infectious diseases were fightable. But as urbanization increases, so do inequalities and the climate also changes and all this greatly disrupts the ecosystem. We must recognize that the emergence of new infectious diseases is a greatly increasing risk.
When should we test for the new coronavirus?
If you have an acute respiratory infection and within 14 days of the onset of your symptoms you have either been in close contact with a person likely to be infected with the coronavirus or have traveled to an area where there is continuous transmission of the virus . Likewise if you have worked or visited a hospital that treats patients infected with coronavirus. In all these cases, you must contact your doctor.