A possible outbreak of plague in the Irkutsk region is widely discussed in the media and social networks. The press writes that several hospitals in Irkutsk have been quarantined, and a mask regime has been introduced at the local plant. The chief sanitary doctor of Russia, Anna Popova, even flew to the region. All this is because of the news about the death of local resident Daria Shipilova, who worked at the anti-plague institute. Both federal and local authorities do not confirm an outbreak of plague.
Are plague epidemics possible in the 21st century? Are the government measures effective?
The host of the BBC Russian Service podcast “What Was It”, Vsevolod Boyko, discussed these issues with molecular biologist, popularizer of science and author of the Telegram channel “Weak-willed Masons” Irina Yakutenko.
BBC: From the heap of messages that I have just listed that we know for sure about what happened in the Irkutsk region, what will we talk about today with confidence?
Irina Yakutenko: This is a very good question, because we only know for sure that something happened. This, it seems to me, is where the reliable information ends. In this case, it is not up to us what information we have. We are completely dependent on local authorities: what they report, we will have such information, because trusting information from unverified sources is not a good thing.
BBC: Okay, then it remains to repeat once again that - according to media reports - we are dealing with the death of a young woman who worked at an anti-plague institute. Also, according to media reports, local authorities, doctors and one enterprise decided to somehow respond to this information. Regional authorities are trying to calm everyone down, as is Rospotrebnadzor.
At the same time, we do not have objective, verified information, any test results that would tell us what is happening there. I think it's important to remember this before we continue this conversation. But let's figure out what the plague actually is.
I.Ya.: Yes, the only approach left is to say that we don’t know anything, but they tell us about the plague. So let's talk about the plague.
The plague, of course, immediately brings to mind images of plague doctors and European cities littered with corpses. 30-60% of Europe's population was wiped out by plague during the Black Death. There was also the Justinian plague and the third plague epidemic, which was so sluggish.
In general, nothing good comes to mind right away, and that’s right. The plague is caused by a bacterium, Yersinia pestis in Latin, and it is a very unpleasant disease that, due to its characteristics, has claimed a huge number of lives in the past.
First, there were no antibiotics in the past. Secondly, the plague is dangerous because it first disables our immune system for some time, that is, it does not allow the body to notice that the pathogen is multiplying. And after the body does detect this, there is already such a quantity of the pathogen that it triggers a hyperinflammatory reaction.
This reaction is largely responsible for such a large number of deaths. As we still remember from Covid, when the immune system gets out of control and uncontrolled inflammation begins throughout the body, the body turns on a hyperinflammatory reaction, which kills the body.
BBC: The media are writing that if there is any outbreak, then we are talking about pneumonic plague. What is pneumonic plague and why is it a prime suspect?
I.Ya.: There are no different pathogens that cause different forms of plague. There are different forms of the disease. They are all caused by the same pathogen, the same plague bacillus. But depending on the method by which the bacterium entered the body, the amount of pathogen and the condition of the person, the disease can take one of three paths.
The first way is the bubonic plague, the “black death”. It was the bubonic plague that was the main form in epidemics of the past. The route of infection is fleas. They get the bacteria from rats, which are also sensitive to the bacteria, and then bite people. Why is it called bubonic? The lymph nodes become inflamed, and these painful, swollen lymph nodes are the buboes. There is also a fairly high mortality rate, but the prognosis is better than with the other two forms, namely septic and pulmonary.
The septic form is a massive proliferation of bacteria in the blood, that is, sepsis. With this form, death is almost guaranteed: the chances of recovery are low even today, and in the past there were none.
The form that everyone is interested in right now is pneumonic plague. It develops when bacteria end up and multiply en masse in the lungs, and this form can be transmitted from person to person. When a person coughs, sneezes, maybe just talks, droplets of saliva and phlegm fly, and there is enough pathogen there to cause disease if it gets on the mucous membranes of another person.
The pulmonary form can develop when the pathogen immediately enters the lungs in large quantities. Well, for example, you inhaled. You work in a laboratory, you work with a pathogen. For some reason your respiratory system is not protected, you inhale. Another option is that if there are a lot of bacteria, then with the bubonic form it can turn into pulmonary.
Or you become infected from someone: in fact, if you inhale from a person who has the pulmonary form, you can also become infected with the pulmonary form. That is, this is not a different pathogen, it is still the same pathogen, the question is where it mainly reproduces.
The pulmonary form is midway between bubonic and septic in terms of mortality. But the problem is that it spreads from person to person. This makes everyone terrified: everything will be terrible, a pandemic like Covid, only a plague.
No. The pneumonic form is found, for example, in Madagascar, a region where plague is endemic. There are pulmonary chains, but they are usually short. One person can infect several other people, but these will not be chains of tens or hundreds of people, because today we have control measures. In addition, when a person is already so sick that there is enough bacteria in his saliva to infect another person, he usually becomes very ill and does not walk the streets.
BBC: For ordinary people like me, the word “plague” remained in school textbooks on the history of the Middle Ages. And then it turns out that some residents of Madagascar are taking her with them in a minibus. Can you please explain how this is possible?
I.Ya.: Plague is a disease that is not specific only to humans. It's not smallpox. The plague did not develop its own devices for infecting people. People are, in principle, a dead-end host for the plague bacillus. The main carriers are small rodents: gophers, chipmunks, prairie dogs, rats.
But since both we and rodents are mammals, we have generally similar immunity mechanisms. The plague adapted specifically to the general mechanisms of mammalian immunity. Therefore, in order for the plague to exist sustainably somewhere, a natural population of rodents and fleas is needed, within which a stable balance is maintained. People in this chain are not needed at all.
Madagascar, which I already mentioned, is a bit of a tragic story. There was no plague there, but it was brought there from India, where there are natural foci. And it turned out that the conditions in Madagascar are very well suited to maintaining this particular ecological balance - rats, other rodents and fleas.
Another place where plague is abundant and constant is Africa. The main region where it affects people is the Democratic Republic of Congo.
BBC: You may have already said this, but could you explain in a little more detail what conditions were, say, in the Middle Ages in order for these epidemics to be maintained and what has changed by the 21st century?
I.Ya.: The main word that is important to us in this case is unsanitary conditions. Because we are dead-end owners. The main ones are rats and fleas. Accordingly, in order for a plague epidemic to be maintained, it is necessary that populations of rats and fleas be constantly present near people in large numbers.
Today we also have rats living somewhere in the basements, but still they don’t run around your apartment, and fleas from them don’t get on you. That is, there is no what it was like in the Middle Ages - where there is a barn with grain, some kind of cellar in which food is stored, because there is no refrigerator, all this attracts rats, there are no repellents, traps do not work well, and there are no insecticides against fleas either.
BBC: A short clarification question: The media wrote that perhaps the deceased girl could have become infected in Southeast Asia. Is Southeast Asia in general and Thailand in particular some place that is specific to this pathogen?
I.Ya.: We need to see if there is some kind of outbreak there. Endemic countries are the Democratic Republic of the Congo, Madagascar, and Peru. This is where most of the infections today come from.
BBC: But then again, ordinary people, using Occam's razor, will probably say that this girl was an employee of the anti-plague institute, and she could have become infected there.
Before discussing the possibility of such an infection, I will ask one more common question: why do we need anti-plague institutes if we have long learned not to live with flea-bearing rats?
I.Ya.: Precisely because foci exist, and they need to be monitored in the same way as we monitor any other infections that can infect a person. Firstly, mutations are possible, and the mode of transmission may change. These are living systems, and living systems can leave the current equilibrium and seek some other equilibrium. Plus, we may, for example, notice an increase in lesions. This may be due to the biology of rats, climate change, and natural hosts begin to migrate.
