How viruses arise and why their massive outbreaks are not accidental: the opinion of the epidemiologist
How do viruses and epidemics arise, what are the mechanisms of infection, and do viruses have a higher goal? Epidemiologist, Doctor of Medical Sciences Mikhail Favorov answered the most important questions for "RBK".
The coronavirus has become a reason for jokes, memes are dedicated to it, songs are composed about it. The virus penetrates not only the organisms of living things, but also pop culture. However, time will pass, and everyone will forget about it, as once they stopped talking about the Ebola virus, SARS and smallpox.
In the 1980s, an outbreak of a previously unknown virus arose in Central Asia. The situation was difficult and tense. The virus was transmitted through contaminated water. Due to its use, the number of cases has plummeted. In most cases, the disease progressed relatively well, but the horror is that mostly women died in the third trimester of pregnancy.
Comprehensive studies began, during which hepatitis E virus was discovered. Its main manifestation is “jaundice”. Now there is a vaccine and various methods of preventing this infection. Then, epidemiologist Mikhail Favorov worked at the epicenter of events.
“I have been to the center of epidemic outbreaks many times - in Africa, Asia, India. But that one, in the city of Dashoguz in the north of Turkmenistan, was perhaps one of the most difficult and tense. I remember we deployed a 30-bed intensive care unit for seriously ill pregnant women. Such an epidemic resembles a situation during a war, only a war is an epidemic of injuries, and here the fight is against an invisible enemy, ”says Favorov.
Today Mikhail Favorov lives in the USA, holds the post of president of DiaPrep System Inc and continues to work actively in the field of diagnosis, control and prevention of infectious diseases.
The virus is the simplest form of life. It is generally accepted that if it is inside a person or an animal, it becomes a living creature - it multiplies and exchanges information. But when the virus is outside the body, it is considered inanimate. We learned about viruses relatively recently, about 100 years ago.
Microbiologist Dmitry Ivanovsky published a study on the existence of a certain substance that passes through filters that trap bacteria, and called it a virus.
While the plague has been known to humanity for many millennia, it has a different nature - it is caused by bacteria, which are a more complex and large organism. Its spread was associated with low living standards and poor hygiene. The mortality rate reached 25%, that is, every fourth died with a pulmonary form.
Among the viral infections, the worst was smallpox, which affected all countries of the world. It was caused by the smallpox virus. The vaccine was invented thanks to a chance encounter with smallpox. The virus of animals that acted as carriers was introduced into the human body, but those vaccinated did not fall ill with the human form of the disease: the body was protected by antibodies from the introduced virus.
The uniqueness of smallpox is that it is an anthroponous virus - only people were sick with it. Therefore, when the vaccine was produced, smallpox was eradicated. In the 1950s, the last contacts with patients were vaccinated in Africa, and since 1978 the virus has been completely eradicated. Smallpox disappears when the last sick person has antibodies - he recovers and ceases to be a carrier.
Another thing is that the main part of viruses is zoonotic, that is, it is transferred from animals to humans, and it is unlikely that such a virus can be completely eradicated. Its first transmission from animal to human is called cross-species transition. So, the bird flu was known to everyone at first, and it was only during World War I that there was a transition to the human population, which caused an epidemic of the “Spanish woman”, which killed tens of millions of people.
Over the past 20 years, we are already witnessing the third attempt to transfer coronavirus to humans. The vaccine, of course, will be found, Mikhail Taborov believes, but one should not expect that the "transitions" of coronavirus and other zoonotic infections will stop even with the improvement of medicine.
“Take one bat, boil in boiling coconut milk for about 15 minutes with green onions, carrots and spices” - this is the recipe for apocalyptic soup, one of many Chinese delicacies.
Bats in China are sold dried and used as an alternative medicine. It was these creatures that caused the outbreak of the SARS (atypical pneumonia) epidemic in 2003, the Ebola virus fever in 2014 and the coronavirus that causes COVID-19. Steven Soderbergh's Contagion perfectly illustrated the chain of coincidences that led to an epidemic similar to the outbreak of the deadly Nipah virus in Malaysia in the late 1990s. It all started with a bat, the virus spread to pigs and then to humans.
“The outbreak is not just an accident, but a coincidence,” says Mikhail Favorov. - And all of them are caused by changes in the environment. Humanity, which had never previously been in contact with bats close enough, suddenly climbed into the cave and caught them. Then the mice were brought to some place, processed, perhaps people even slept with them in the same room. Zoonotic infections are usually transmitted under two conditions: a large dose of the pathogen and fairly close contact. Another incentive may be that this year the mice had a so-called epizootic - an outbreak of infection. And this means that a large dose fell on a person - millions of viral particles. Among these particles is always a variation that attaches to the receptor in the human body and enters the cell. Moreover, the first contact is the most difficult and often leads to the death of the first infected, because all systems and enzymes are different, the virus is completely not adapted to humans and quickly leads to the destruction of the body. Mice themselves do not get sick, but serve only as carriers. ”
Heat of our bodies
In terms of population density, China and India are superior to all other regions of the planet, and the diversity of animal species in Africa is so great that most of us are unlikely to know about the existence of some of them, for example okapi, wyverre, and arm-legs.
Both rare animals and population density become additional incentives for a high rate of spread of infection. Viruses do not infect Chinese or representatives of other nations separately; viruses are apolitical and lack religion. They can adapt to any changes in the environment no worse than humans. All they need is the warmth of our bodies and, possibly, certain receptors.
Coronavirus can be called in some way age-specific - the disease in isolated cases affects children, and mostly elderly people die. One of the theories put forward by experts suggests that there is a certain receptor that appears only in adults.
This “traitorous” receptor helps viruses attach to the cell in large volumes. But this is only a hypothesis, and in order to confirm it, a lot of work needs to be done to study viruses. Their structure is complex and diverse. Viruses vary in form, according to the mechanism of replication (damage to the body), but the biggest difference is that part of the viruses has the main nucleic acid - DNA, and the other part contains RNA. These are two different "natures", and the difference between them is much greater than between elephants and bacteria - both of them at least have cells that contain DNA.
The outbreak is not just an accident, but a combination of circumstances.
Each virus has its own characteristic, which it uses to parasitize on a living creature, and what the disease will lead to depends on this interaction. If the virus is “ours,” anthroponous, then it usually does not cause global epidemics (with rare exceptions of the same smallpox). It causes a disease that leads, for example, to a chronic disease, as in the case of hepatitis B and HIV. If the virus is zoonotic, then it somehow leads to an outbreak.
Everything is closed: markets, shops, metro. Public transport stops are completely empty. Along the sidewalks only trash driven by the wind disappears, disappearing in a yellowish haze. It’s strange when you consider that millions of people live in the city. Occasionally people in respiratory masks appear on the street, some are made from improvised means.
Once having seen such a picture, it is hardly possible to confuse the epicenter of the spread of a respiratory disease with something, and you need to defend yourself immediately.
“Ways to protect against a virus in the global and local sense depend on how the virus spreads and what its nature is,” Mikhail Favorov explains. - During the outbreak of hepatitis E, the virus was transmitted through water, so it was advisable to stop any contact with water. When a respiratory outbreak occurs, as it is now, it is more difficult to control. The Chinese acted very competently: they isolated a multi-million city. This is an ancient proven method of combating the epidemic, which was found back in the Middle Ages, when they fought against plague. You need to wait until people get sick or “get immunized” - the virus tends to adapt and ceases to give symptoms, while the human body produces antibodies against it. When there will be more than 30% of people with antibodies, we can say that the epidemic will end soon. ”
In order to protect yourself and your family during a respiratory epidemic, the main thing is to be at a distance no closer than 2 m from a sick, sneezing or coughing person, wash your hands every two hours, ventilate the premises, and minimize contact with people.
“A respiratory mask may well protect, but the problem is that it is reliable for only 20 minutes,” Taborov recalls.
The history of mankind has tens of thousands of bloody wars, but the most terrible in losses, perhaps, are wars with parasites. According to some reports, more people died from the plague than as a result of all wars taken together - about 186 million people. One Justinian plague, the first recorded in history, killed 100 million people.
The development of protection against biological threats is expensive, therefore vaccines are created only for those viruses that pose a real danger. Moreover, viruses get used to some vaccines, become resistant and change their structure, so humanity has to be constantly on the alert and come up with something new.
A respiratory mask may well protect, but the problem is that it is reliable for only 20 minutes.
In microbiology, this is called the arms race between the virus and humans - when the virus gets used to it and humans develop a more sophisticated type of vaccine. This can be attributed to the influenza virus, which can constantly change its antigenic structures, eluding immunity or vaccines.
For example, there was originally influenza A from which the vaccine was invented. But microscopic creatures, or rather their nucleic acids, have picked up the key to existence in the body. This is how type B flu appeared. But not all viruses can “decode” the vaccine. For example, measles virus, to which there is a vaccine, does not change for centuries and cannot survive in the body in the presence of antibodies.
In biology classes, we were told that life is the way nucleic acids exist. One of the options for the existence of nucleic acids is viruses that live on other organisms.
They do not care about our well-being at all, they are trying to adapt, like all living things on the planet. The only thing worth thanks for is the evolutionary perfection of the human immune system. For centuries, when any infection appeared, the human body produced antibodies and formed cellular immunity.
Everyone knows that if you keep a person in a sterile environment, and then let him out into the street, he will soon die, because he will not have a mechanism for generating protection. But this is not the goal of viruses, but rather a side effect.
Predicting the occurrence of virus outbreaks is even more difficult than talking about higher meanings. This is always a unique situation that occurs as a result of a change in the state of the environment in which a person falls into new conditions of interaction with other species of animals.
And today, the anthropogenic impact on the environment has reached absolutely disparate proportions compared to previous generations, moreover, man as a species is constantly growing. Scientists have the opportunity to observe the attempts of viruses to make a cross-species transition due to laboratory tracking methods.
Doctors eliminated smallpox and almost defeated the polio virus - this inspires hope that at least an agreement can be made with the coronavirus. No matter how this relationship develops, it is worth remembering: as long as a person exists as a species, there will always be those who want to parasitize on him.
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