Epidemics. Where Do They Come From, What Fuels Their Spread, and When Will We Defeat Them?

20 February 2020

Can we stop epidemics? Is vaccination mandatory? Why do diseases that seem to have been vanquished forever reappear? And what is happening with the HIV epidemic in Russia and around the world? AIDS.CENTER gave Mikhail Favorov, Doctor of Medicine in Infectious Diseases, an international expert in public health, epidemiology and laboratory diagnostics an opportunity to answer these and other questions.

To start off, let's get one thing clear. How do epidemics appear?

The standard definition of an epidemic is a widespread occurrence of an infectious disease in a given population within a certain period of time. However, we must specify here what "widespread" means, what kind of disease it should be, and what is meant by "population" — that of a city or a country. This term is very generalised, and is often used to strike fear into people.

We are all a part of an ecosystem. For example, there were almost no measles epidemics in the world until the end of the 20th century. That's because it's been there for a very long time. It has existed as far back as antiquity. People would catch it and develop immunity. There would be severe cases, including fatal ones, but not epidemics. The infection would spread sporadically, and the disease was controlled by natural immunity. However, after the rise of sea travel around the 18th century, measles was brought to Polynesia. A real epidemic broke out around that area, as the locals had not developed any immunity to it. Adults and children alike died in vast numbers. The same happened in the Philippines. Therefore, environmental changes, the wide use of ships, and the development of civilisation led to the spread of infection.

But infections learn to "adapt" too, right? This is a fully fledged relationship then, isn't it?

The interaction between a disease-causing agent and human beings is a relationship between macro-organisms and micro-organisms. A microbe's main purpose is to multiply and continue its existence. So there is no point for it in killing the host. Meaning the microbe needs the disease to be mild and to last as long as possible. Now, as a result of the social and environmental pressure that humanity has been exerting on microorganisms in a bid to eradicate them, the real problem is mainly infections that existed relatively dormant for a long time. For instance, with viral hepatitis C, most severe complications that can be fatal gradually develop over the course of 20-30 years.

In 1918, a Spanish flu epidemic broke out that killed millions of people. There was a recorded case when a family got on a subway car to get from one end of New York to another. The whole family died on the way. This goes to show how poorly protected they were against the infection.

This happened during that time because transport was rapidly developing around the world at the time. Never before had humans moved around so much. Besides, the First World War led to a steep deterioration of nutrition and living standards in general. There is always a set of factors behind any epidemic.

The crucial thing for an epidemic is the number of susceptible individuals. If a child is exposed to an infectious agent, like the one causing measles, that neither that child nor the other kids in the kindergarten have ever encountered, and they were inoculated with a vaccine that had been stored improperly, the incidence of the disease will be high. On the other hand, back in the eighties, my mother — I'm a third-generation epidemiologist by the way, conducted a study on meningococcal infection. It showed that if 30-40% of children in a kindergarten are immune, there will be no outbreak except isolated cases.

By the way, I was among the first people on whom the vaccine against meningococcus was tested, as my mother was involved in its development. It was common practice back then to test vaccines on your own children first.

Do you mean that 30-40% of people need to be vaccinated to avoid an outbreak of a disease?

No, everyone needs to be vaccinated against everything. Otherwise, children, for instance, could get measles and die of necrosis. If we take a kindergarten, 93% of children there should be vaccinated against measles, as it is highly contagious. In this case, there will be no outbreak, only isolated incidents. By the way, Russia has a very good vaccination schedule.

I particularly would like to urge everyone, both men and women, not to shy away from vaccination against the human papillomavirus, which is especially important for girls aged seven to nine. Yes, the vaccine is expensive, but it'll protect you from cancer. Talk to those who have experienced this terrible disease. I'm sure you won’t regret parting with a hundred dollars for that. I also highly recommend vaccination against pneumonia for people over 55.

And what is the danger behind avoiding vaccination in global terms?

The number of people avoiding immunisation speaks to a growing social problem. There are those that refuse to be vaccinated for religious reasons, while others refuse to do it for personal ones. If you don't want to do it, fine, but you will have an infection outbreak.

Back in the late seventies and early eighties, my mother wrote in the Rabotnitsa magazine that people tended to avoid vaccination against diphtheria. As a result, dozens of thousands people died in the nineties in the former Soviet Union from a disease that the rest of the world no longer had due to their refusal to get vaccinated.

Avoiding vaccinations is like driving under the influence. Under certain circumstances, everything is fine, but if something irregular happens, people end up dying. Yes, one has the right to refuse to vaccinate their children, but it may kill them. Besides, such people create a population of susceptible individuals, thus harming society.

What is a pandemic? How is it different from an epidemic?

A pandemic is an extremely rare thing. This is the highest form of the epidemiological process when the whole world encounters a new agent within a short period of time. In scientific terms, the Spanish flu was a pandemic.

Nevertheless, this word is sometimes used in a broader sense to attract attention. Is HIV a pandemic? Probably so, if we talk about the scale of its occurrence. Although this infection is slow because it lasts decades, it is still a pandemic, as there is no country where they don't have HIV. In some parts of Africa, more than 30% of the people are infected.

Can we also call hepatitis C a pandemic? Yes, we can, because it, too, is everywhere. However, it takes 20-30 years before the infection starts being life-threatening.

"An article stating that vaccines lead to autism was published in the medical journal "The Lancet". It later turned out to be fake: no research had really been conducted, and the results had been simply concocted"

Have you ever met anti-vaxxers personally?

Sure. I once participated in a meeting in Washington where this group of people advanced the view that the drug Thimerosal, which is used as a preservative in vaccines so that they can be stored longer, can negatively effect people's health. In theory, it can. But these losses are incomparable to those that can occur when using a spoiled vaccine, as well as in case of having no vaccination at all or a violation of vaccination procedures. Interestingly, following the incident, companies all over the world stopped manufacturing vaccines containing thimerosal. This has made vaccines twice more expensive. But who cares?

Unfortunately, I've been having to deal with anti-vaxxers increasingly often in recent years. They are everywhere — Russia, Central Asia, the USA and so on.

Is it true that pharmaceutical companies profit from manufacturing vaccines?

That is a lie. First, the total profit for all vaccines in the world is approximately equal to the profit for a single medicine for heartburn such as Almagel, for example. Second, vaccines are such a painful and socially sensitive business that there are only a few manufacturers in the world, although there used to be dozens before. It's not profitable to invest in vaccines, so no one wants to.

Yes, there have been bad incidents in the history of vaccination, but everything has its flip side. For example, in 1955, 164 people were left paralysed in the United States due to some faulty production of a polio vaccine. A similar thing happened in 1976, when 25 people died after receiving a swine flu vaccine. The next incident took place in 1999, when nine children suffered from intestinal obstruction after getting a rotavirus vaccine. Fortunately, no one died.

Today, all vaccines are almost equally safe, but the important thing is how they are stored and transported. Don't forget about the human factor. Nevertheless, it is believed that the risk of a vaccine causing complications is slightly less than ten cases for one million vaccinated people. Moreover, even redness, swelling or pain at the point of injection are considered complications. This is often just a mild allergic reaction.

I experience such a case in my practice. A young man was vaccinated against hepatitis B, and the next day, he was hit by a car. His parents filed a suit against the vaccination specialist, claiming their son had not been attentive enough due to complications caused by the vaccine. There are always those who are just looking to make a quick buck.

How about vaccines being made from aborted babies? That's not true either, is it?

This is an absolute lie and evil propaganda by anti-vaxxers. It's not the first time I'm hearing this. I usually answer this in my own natural way, saying that it is the anti-vaxxers who were made from aborted babies. Anti-vaxxers are social trolls. Their influence has grown with the rise of the internet culture. They get satisfaction from pitting people against each other.

There was a really shameful story. The journal "The Lancet" published an article saying that vaccines lead to autism. It later turned out to be fake: no research had been really conducted, and the results had been simply concocted. The journal then pulled down the article and apologised a hundred times. Anti-vaxxers must have really enjoyed the situation.

How are vaccines made? Is it true that vaccines against the swine flu are produced by growing the virus in chicken eggs?

The scientific term is chicken embryos. Yes, that's true. Kidney cells of marmoset monkeys can also be used for that. All these tissues were discovered experimentally and modelled so that the pathogens grown on them work like vaccines in the human body. Human tissues are not used for this.

Are vaccines expensive?

The cost of one vaccine starts at 16 cents. The HPV vaccine costs almost a hundred dollars. And that's only for supplies. With transportation and other additional expenses, the price can rise to 300 dollars. Vaccines that have been used for many years cost very little, new ones cost hundreds, and the latest ones cost thousands.

The HIV vaccine is currently still being developed. Please, tell us more about it.

The vaccine was made and tested in Thailand. It provided some protection, but only in a few cases. It turned out that there are certain antibodies that help protect against HIV. The 17% of the human test subjects who happened to be protected by the vaccine were found to have them. Using the reverse analysis method, it was determined which proteins these "protective" antibodies belong to. These proteins were incorporated together into a single "mosaic" protein. This is now a new vaccine candidate that is going be tested.

Then they isolated proteins for the production of these antibodies, made a genetically engineered protein and fused these pieces together into one molecule. New trials will soon begin. Hopefully in 10 years, we will get the vaccine. Of course, it'll take a huge amount of money, but it'll be worth it. Because as long as humans continue to have sexual relations, there will be HIV transmission.

Another option is to put all infected people under treatment. Then they will not infect others, as the virus cannot be transmitted through sex when you're receiving the therapy.

What is the current situation with the HIV epidemic in Russia?

The incidence rate is getting higher. Many of the cases are not being registered, and infected people may simply not know that they have the virus. The main question now is how to identify these people. Today, 60 new cases per hundred thousand people on average are recorded every year in Russia, 40 in Ukraine and 20 in Estonia, where the number was 50 in 2006. Estonia has made this leap forward due to proper HIV identification and treatment measures. By the way, the HIV prevalence rate in the Central Asian countries is also about three times lower than in Russia.

Right now, Russia needs to achieve three things: to provide treatment for all HIV-positive people, wherever they live, to identify everyone who has not yet been identified, and to establish a reliable supply of quality medicines. If we do that, HIV will be defeated within ten years. Unfortunately, the number of people living with HIV in Russia has increased by more than twice since 2005. Currently, at least 1% of the country's population is HIV-positive. This is a disaster. I don't know what the reasons for this high level are, but I see that no one is addressing the issue right now.

Once, when I was visiting a virology institute in one of the Sub-Saharan countries before HIV drugs were even developed, I noticed an announcement on the lobby wall. It said that the institute's employees were entitled to seven days off work a year in addition to their regular two-week vacation to attend funerals. That's because so many people were dying of AIDS. Seven days was the limit, otherwise the employees would go to funerals all the time, and operations would just stop.

The same thing will happen in Russia if we don't address this problem. Given that the number of registered cases has already doubled, what are we going to do in the future? It will be four times higher in ten years.

What other diseases endanger humanity today and in the nearest future?

Infectious diseases that were one of the main causes of death at the beginning of the last century have already moved down to the seventh or eighth place. Of course, the answer to this question depends on what criteria we are using to assess the impact of a particular disease. I prefer the "lost years of life" criteria. The main figure is how many young people die.

Major outbreaks may occur with zoonotic diseases that normally do not affect people, such as anthrax, for example. When a person gets it, the disease takes a very severe form. The reason is that the microbe is used to living in a cow, and feels confused once it enters the human body. The microbe starts thinking, "There are different enzymes here, the systems are different... Where am I?" The same happens with the Ebola virus, whose main host is not humans, but bats.

Humanity is currently endangered by the gap between the rich and the poor. Microbes don't care about that. They circulate between these two populations. Meanwhile, the poor cannot afford to carry out the same anti-epidemic measures that rich people take. The role of the state in infectious disease control and prevention is crucial. This is characteristic for any country in the world, but especially for the least developed.

And what epidemics are considered now defeated?

I believe that the HIV epidemic is coming to its end around the world. All countries, except Russia, are showing signs of a decrease in the incidence rate. I think that after a while, the number will stop growing even in Russia, when they finally decide to fund drug supply sufficiently. If people remain untreated, they continue to spread the infection. This is outrageous. For me as an epidemiologist, providing HIV treatment means stopping the transmission of the virus.

"Once, I was visiting a virology institute in one of the Sub-Saharan countries. Employees there were entitled to seven days off work a year to attend funerals. That's because so many people were dying of AIDS. The limit was seven days; otherwise, people would go to funerals all the time"

When smallpox was brought into North America, a devastating epidemic occurred there. Smallpox epidemics had happened earlier in Europe, but they had been self-regulating, that is, they would break out and then go away on their own. Smallpox was only finally eliminated through vaccination.

There was an Ebola epidemic in Sierra Leone a few years ago. It took great efforts to defeat it, but now, it has come back to strike neighbouring Congo.

All epidemics are eventually eradicated, either by immunising people or after a significant amount of people have gone down with the disease. Unfortunately, many people die from the second way.

What are the criteria for declaring an epidemic eradicated?

There is no clear answer here. I guess if there are three infected people left, then the epidemic would be declared to be over. If there are still three hundred of them, things will depend on the population and what type of disease it is. If you have one case of smallpox, this is an epidemic. If there are three hundred people with runny noses, it's not.

Are scientists today still discovering new dangerous viruses?

They do, but I'm not really worried about them, because there are few clinical cases. There is much talk now about bacterial resistance. For example, they say that HIV is developing resistance to drugs, or that bacteria now have high antibiotic resistance. That is true, but, for example, in case of bacteria, the problem is not so much people as animals. Resistant forms of bacteria appear because growth hormones and antibiotics are used when raising pigs. People also have their role in this, but it can be limited.

What are the latest discoveries?

New pathogens are being discovered, but there is nothing special about them. The last to cause a worldwide stir on infectious diseases was the Ebola virus, but this has been known since the mid-seventies.

As a practitioner, I enjoy reading about new pathogens. But I also like to read about the discovery of bacteria living, for example, in spiders. This is interesting and important in science but difficult to apply in practice.

I participated in the discovery of hepatitis E. I worked with patients with the infection, and detailed its clinical characteristics. The virus itself was described by the Institute of Poliomyelitis researchers Mikhail Baloyan and Alexander Andzhaparidze and their colleagues.

Hepatitis G was discovered a few years later. Everyone was alarmed because of the new agent. Tatiana Yashina and I conducted a study based on patients' materials in Moscow and showed that although this agent does exist and can be transmitted from person to person, it is not heterotopic, that is, it does not cause liver damage. We would joke then that it's a small and kind virus looking for a disease. So the newly discovered agents do not necessarily cause terrible outcomes.

Why do previously defeated illnesses such as measles come back?

The measles vaccine is highly effective, but not effective enough to violate a vaccination plan. Besides, it is quite sensitive to external factors. If a vaccine is heated, which happens quite often, it will not provide long-lived immunity. Moreover, as a result of people avoiding vaccination, a susceptible population group is formed. Unvaccinated and poorly vaccinated people can trigger a measles outbreak.

How many vaccinations does a person need in life?

There are about 14 vaccines that need to be received with a certain frequency. That makes 17 adults. Some of them are administered only once in early childhood, while with some of them, like the flu vaccine, for instance, repeated vaccinations are required. For example, the hepatitis B vaccine is given in three shots, while the hepatitis A vaccine requires two doses.

In the US, people get vaccinated against the flu for free at pharmacies. It's covered by insurance. Moreover, those who have been vaccinated are given a ten-dollar coupon. This is beneficial for insurance companies: if a person gets sick, the treatment will take much more money. I usually use this coupon to buy a bottle of wine.

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