Let me begin with a disclaimer. Our knowledge of viruses and vaccines is imperfect as is my own understanding of that knowledge. This is my best understanding of the current science.
The Covid pandemic has caused hardship and conflict far beyond the actual medical manifestations of the virus itself. For that reason, I am writing this post to talk about the basic scientific concepts related to viruses and vaccines. I will not address the social and political phenomena beyond saying that this is not the first time there has been conflict about the measures necessary to slow an epidemic. For those who are interested you can read the Wikipedia article about the 1771 Moscow plague riots here. https://en.wikipedia.org/wiki/Moscow_plague_riot_of_1771
It is important to understand that viruses have evolved side by side with complex organisms for millions of years. One should not misinterpret their simple structure as a lack of sophisticated and complex mechanisms. Viruses are essentially genetic material wrapped in a delivery system so the level of complexity is limited only by the potential of their genetic material which is almost unlimited.
Viruses are different from bacteria in that they are not capable of reproducing on their own. Since viruses are nothing more than a package of genetic material they require a host cell to provide the mechanisms to reproduce. There are also many different kinds of viruses. A retrovirus like HIV (which causes AIDS) and HTLV (which causes lymphoma) actually reprograms host cells while influenza viruses and coronaviruses hijack the cell mechanisms to reproduce themselves. We won't go into retroviruses, which are extremely difficult to treat, and focus on common RNA viruses. Notable human diseases caused by RNA viruses include the common cold, influenza, SARS, MERS, COVID-19, Dengue Virus, hepatitis C, hepatitis E, West Nile fever, Ebola virus disease, rabies, polio and measles. These are the viruses most commonly and effectively treated with vaccines.
Here are some basic FAQs about these viruses and the vaccines to treat and prevent them.
1) What is a novel virus like the Spanish Flu of the early 1900's or Covid-19 and why are they so dangerous? Viruses mutate very quickly but once you have had a virus you will likely have some immunity to mutations. Seasonal flus are variations of flu viruses that have infected humans before. They tend not to kill as many people or make them as sick because our immune systems have seen something like them before. A novel virus is a virus that the human population has never seen before. It has jumped from another species. The Spanish Flu of the early 1900's was a swine flu that is still present in the human population but its subsequent mutations are less harmful now as we discussed earlier. The Covid-19 virus is originally thought to come from bats and is new to the human population.
2) What are swine and avian flus and why are they important? Swine flus come from pigs and avian flus come from birds. Each of them presents a different danger and challenge. The swine, avian and human flu strains are not exactly the same but similar so they sometimes jump between species. Birds are a problem because they travel vast distances and are the perfect mechanism for spreading viruses. Pigs are less mobile than birds but exist in very close proximity to humans.
3) Are all viruses airborne and what about masks and hand washing? No, some viruses require physical contact while others can be passed by breathing the same air. In addition, many viruses can be spread both ways so you can get them from either breathing the same air or touching a surface with virus on it. It's very difficult to protect yourself from airborne viruses and masks offer limited protection to the wearer even if worn properly. What a mask does do very effectively is reduce the ability of an infected person to spread the virus. Hand washing is important because some viruses can survive on surfaces for hours or even days. Hand washing is critical to avoid infecting yourself with viruses present on common surfaces. Soap and water works best because the outer shell of viruses is lipid (fat) and protein. Soap is very effective at dissolving the outer layer of a virus and killing it. Alcohol and chemical based disinfectants are not always as effective as soap.
4) How do vaccines work and are they completely safe? There are many different types of vaccines but the basic mechanism is the same for all of them. Vaccines introduce components found on the outer coating of viruses which our immune systems recognize as foreign and cause us to develop an immune response to fight the actual virus later. The first vaccines were made by killing the actual virus and injecting the dead virus. Vaccines today have very different mechanisms to introduce those components but the basic immunological response is the same. Vaccines are never 100% safe. One of the reasons for testing a vaccine it to check to see how safe and effective it is. If its effectiveness is high and side effects are limited then it is deemed worth the risk. Basically it has to save a lot more people than it harms.
5) What do quarantines and lockdowns do and what is herd immunity? Quarantines and lockdowns slow the spread of viruses. Since viruses have a limited ability to survive outside of a living organism reduced contact and increased distance between people will reduce the spread of a virus. Herd immunity is a condition reached when enough people are immune to the virus either from previous infection or immunization so that the people who remain cannot spread the virus to each other very easily. One question that policy makers face is whether to allow a virus to spread unchecked so herd immunity will be reached more quickly and the economic impact of quarantines and lockdowns are eliminated. Sweden used this strategy. The problem is that more people might potentially die because the healthcare systems could get overwhelmed and more people will be infected before a vaccine is developed.
Viruses will be with us and challenging us for the foreseeable future. We never know when we will have more epidemics but we are sure to have them.
