Respiratory infections like colds and flus are caused by vast numbers of viruses. As viruses infect us all, they cause herd immunity and stop propagating. Usually, they do not completely disappear, but come back in new waves causing small number of infections. We have learned to live with colds and flus, albeit they are an important contributor to life lost to illness (sick leave, etc).
When a new virus appears, nobody is immune. Thus, the virus is free to infect the entire population in a relatively short time. Even for a virus that is mild and causes serious illness only in very rare cases, infecting a vast number of people all at once will result in a spike in deaths and seriously ill patients.
Every time a virus replicates, it can change its genetic code a little bit. Some of these random changes will give the virus interesting and useful abilities, like, for example, to infect a new species. If the new species is in close contact with the old host when the mutation occurs, the virus has the chance to jump. This is how the epidemic starts.
For reasons I do not fully understand, China and South-East Asia seem to be a prolific ground for such jumps. Several new viruses have been tracked to this area and, most likely, many of the epidemics of the past also originated there. China and nearby nations have played no politically motivated role in this natural phenomena.
It may well be that some cultural habits do play a role. For example, Chinese are more adventurous with their food. They are more likely to eat undercooked bat lungs, frog intestines or other delicacies. They are also more likely than many other nations to cook and process these animals with bare hands and neglect scratches and bruises on the skin when doing so. On farms, people and animals often live together, with caregivers walking barefoot in excrement, blood, etc. While, for the individuals such habits can actually be healthy (fewer allergies, asthma or autoimmune disorders), the lifestyle may offer viruses an opportunity to adapt to humans.
In the West, we eat factory farmed stuff. While not quite there yet, in principle, we tend towards a world where our food is formed of sterile clones of the same thing. All pigs are clones of the same pigs, all cows clones of the same cow, all chicken are clones of the same chicken and so on. In Romania, for example, the European Union has recently made it illegal for pigs to reproduce naturally. All porcine reproduction is to take place in EU standardized farms. In the past, when a farmer wanted piglets, he would call on a friend who owned a male pig and introduce him to his sow. The male would be walked through the village to the house of the female, where reproduction takes place or if the male was more valuable, the female would go to the house of the male and there was a price to be paid for the service to the owner of the male pig. This is now illegal. I do feel sorry for the pigs who have to reproduce through artificial insemination and for the farmers who have to pay, sometimes more than the cost of a pig for the insemination procedure.
For viruses though, the disappearance of privately owned pet pigs that are occasionally eaten, might not be not great news. If the pig and the man do not stay nose - to snout, when the pig has a cold, he cannot pass it to the man. Most viruses cannot mutate from one species to another — but a few do. Recently, we have seen the avian flu (mutated from birds), the swine flu (mutated from pigs) and now the coronavirus.
Modern pig farms where animals of nearly identical genetics are catered to by machines and very few people offer less opportunity for viruses to change species. If this is, overall, a good or a bad thing for humanity and nature, it is still to be debated.
Anyway, the conclusion is that viruses change species. This often happens in China and they go on to spread around the world.
== This isn’t the first time ==
Humanity has seen countless pandemics. The coronavirus pandemic is not the first pandemic and it will not be the last. This is, however, the most deadly pandemic since the Spanish Flu of 1918, and the best monitored. Due to recent advances in PCR (polymerase chain reaction), it has been more closely monitored.
What is unusual, is that it appears we have understood this virus so well that we even know the market where it adapted to infect our species. The market in itself is not unusual for Asia. Animals are sold -- some dead, some alive in a mix of blood, sweat and excrement. People — salesmen and customers -- are in close contact with each other and the animals. The animals, in a state of stress and near death have weakened immune systems. This makes them more susceptible to human viruses. Perhaps, when human and animal viruses meet in the same organism, they can exchange some genes which can help them adapt to infect humans. This is a natural phenomena.
The flu tends to cause multiple well observed epidemics. Coronaviruses, generally, gave 10-15% of colds. They were not well tracked before because the colds were not severe enough to warrant attention. The exceptions to the rule are MERS and SARS who are rather deadly and have been successfully stopped.
The most famous flu epidemic is known as the Spanish Flu of 1918. It consisted of three different waves. This flu ended more lives than the first world war. This is what we are afraid of. Today’s coronavirus has a similar ability to spread, but it kills fewer people, and the average age of the dead in each country is so far within a few years of the life expectancy.
The Spanish flu was different. It killed mainly young adults. Pregnant women were particularly vulnerable, with some authors citing a mortality of about 70% among pregnant women, with a good fraction of survivors losing the baby.
Today, we have a flu vaccine. We did not have that in 1918. Various treatments have been tried, but it appears nothing worked. We were in a similar situation to what we seen now with COVID-19. We don’t have a cure.
In 1918, the one thing that appeared to work was blood transfusions. Transfusing the blood of people who had recovered from the flu into newly infected patients would pass on to the recipient the antibodies of the donors, resulting in milder infection and better change of recovery.
It is amazing that we are considering such barbaric treatment methods today.
== To kill or not to kill? This is the question of viral evolution ==
Cold and flu viruses had been able to conquer the world long before planes and trains would help them travel fast. They’d go from house to house, from village to village, at the speed of a donkey or slower than a snail. Yet, sooner or later, the often end up taking over the world -- the whole world.
Once a virus becomes adapted to humans, it continues to evolve. The virus “wants” to live and spread. It wants to colonize new hosts. For this, the old host has to be able to carry the virus to the new one. Thus, a virus who kills the host will not be very successful. The virus will go in the grave with its dead host and spread no further. However, a virus that causes mild illness allows its sick host to party and dance, to meet people and kiss friends and infects a lot more people. Thus, a less deadly virus will be more successful.
If a mutation appears, making the virus less deadly, but not sufficiently different to be immune to the antibodies of the main viral population, the less deadly virus will spread more than the deadly version of the virus. Eventually, the deadly version will die out and the more mild one will take over the world — unless, maybe, an ever milder evolves. This is why, cold viruses that have infected humans for a long time don’t cause very serious illness.
Evolution in the opposite direction is also possible, but not likely. It isn’t always easy for a virus not to kill. The natural thing for a virus to do is to multiply — an exponential process that can easily grow out of control, until all cells of the host have been killed. The host will die when only a relatively small fraction of its cells no longer work. Thus, the virus has to be very careful to not kill us. Usually, they do a pretty good job of being careful.
== The role of globalization ==
In the past, at the start of an epidemic, the new virus would progress with relatively low speed. He’d move from house to house and from village to village, at most at the speed of a donkey. Usually, it might have been more like the speed of a snail, with many stops and breaks. This way, it would take a long time and many cycles of viral replication to go around the world. Along the way, the virus would learn to be gentle with its hosts, causing milder and milder illness as it went along.
This gradual transition towards a more mild illness was seen in the Spanish Flu of 1918. People infected later fared better.
We have seen a similar effect in Wuhan in 2020. In Wuhan, however, the more mild illness happened when the quarantine was imposed. It is thus possible that they were not caused by a viral mutation, but by the quarantine itself. People who go to work through wind and snow often develop more severe forms of the cold when infected. We have seen this in World War II. Adenoviruses, that usually cause nothing but mild colds, were responsible for many cases of pneumonia among young and healthy soldiers who were forces to live in cold and damp trenches for a long time.
In the same way, overworked doctors are seen to have more severe forms of COVID-19 and have higher mortality rates. It is thus possible that Dr Li Wenliang who first discovered COVID-19 was not even killed on purpose by the Chinese police. He was only jailed — certainly a stressful experience. Just like soldiers in trench warfare who develop deadly pneumonia from a mild adenovirus, Dr Li Wenliang would be expected to develop a more severe form of pneumonia after a stint in jail than after a sunny holiday. Furthermore, upon release, the government issued the doctor with an apology and he was sent back to work, not on holiday. Most free men would not willingly work for a government that put them in jail for fake reasons. Statistically, these aspects would have certainly contributed to Dr Li Wenliang’s death even if he was not actively killed.
The quarantine should help by making people stay home, thus decreasing the severity of the illness. It may be beneficial even if we don’t consider the effects on contagion. Considering that hospital care is very expensive, especially if it comes to using one of the respirators on very short supply, the productivity lost in the quarantine could be less than the cost of the hospital care that is saved as long as the quarantine period stops before the supply chains break in an irretrievable fashion.
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