February 23rd, 2020
This week I have decided to talk about about another disease, since so many of you liked my post about the flu (shameless plug: if you haven’t read that one go check it out!). In my microbiology class we talked a little about Polio while we were discussing vaccines. It sparked my interest and I wanted to do more reach about it, so I decided that I would make this weeks blog post about polio and its vaccines. What got me really excited about this disease, was that it is looking very possible that we can eradicate Polio off that face of the earth in the next couple of years! I don’t know about you, but I think that is amazing and shows the power of modern medicine.
What is Polio?
First off what is Polio? Polio, or poliomyelitis, is an infection that is caused by the poliovirus. Most people who are infected with the poliovirus have an asymptomatic infection, meaning it causes no visible signs or symptoms. However, this makes the disease very contagious because people can be infected with the poliovirus but have no idea, and thus take no precaution in trying to not transmit it to someone else. However, if someone does show signs and symptoms they are likely to be similar to that of the flu (sore throat, fever, headache, and just a general feeling of malaise). Rarely, this virus can cause very severe nervous damage and cause paralysis, difficulty breathing, and sometimes death.
Polio is transmitted by person to person contact. It enters the mouth of the person. Most commonly this is spread when someone directly touches or inhales fecal mater (poop) from an infected person and it enters into their mouth. This virus can also be inhaled from droplets that are coughed out from a host. The virus colonizes on the tissues that line the host’s throat and gastrointestinal tract, and can then enter into the bloodstream.
Polio Vaccinations
Polio used to be a fairly common disease, but thanks to its effective vaccines it has been nearly eliminated. Let’s discuss these life saving vaccines in a little more detail. There are two vaccines that I will examine in more detail. Both of these vaccine result in the immune system creating an antibody response, and thus protection from future encounters with the virus.
The first polio vaccine that I will discuss is the inactivated polio virus (IPV). The IPV vaccine was created in the mid-1950s and was also called the Salk vaccine, which is the name of the doctor who found it. This vaccine is an inactivated vaccine, meaning it contains inactivated poliovirus strains. The virus has been modified so that it can no longer replicate, and is thus not infectious. The pathogen does retain its immunogenicity, which helps your body form proper immune response to it. However, the drawback of inactivated vaccines, and thus the IPV vaccine, is that the magnitude of the immune response is limited. As a result, you need to get a regular booster dose to ensure that you have acquired an adequate immune response to ensure that you are protected from the poliovirus.
The second polio vaccine that I will discuss is the oral polio vaccine (OPV), which was developed in 1961 by Dr. Sabin. Unlike the IPV vaccine, which was an inactivated vaccine, the OPV is an attenuated vaccine. An attenuated vaccine is a vaccine that contains a weakened form of the virus. So, the virus is still able to replicate in the host, but since it is weak, your immune system (unless you are immunocompromised) is able to easily and effectively eradicate it from your body. An advantage of these types of vaccines, is that unlike inactivated vaccines, the immune response to these is usually long-lasting. Moreover, because the vaccine injects the naturally occurring virus (wild-type virus) into your body, your immune system creates a more effective response. Specifically with OPV, your immune system is able to provide better mucosal immunity. Thus is you were to become infected with the virus again these antibodies are able to eliminate the virus before it can colonize the cells in your throat and gastrointestinal tract.
Both of these vaccines were effective in their effort to eliminate polio. However, OPV is the only vaccine that can truly eliminate polio. With IPV the virus is still able to replicate in the host’s throat and gastrointestinal tract and can thus be shed by their feces and spread to another susceptible host. Because of this vaccine by the 1980s wild-type (aka not mutated/ naturally occurring forms) polio was eradicated from the United States and by 1991 it was eradicated from the whole Western Hemisphere. I think that this is just amazing and very important. It is amazing how far science has come that we are able to create vaccines that help completely eradicate a disease from certain areas. It is important because it shows what happens when everyone/ majority of the population in a certain area vaccinates their kid. Due to the anti-vaccination movement many diseases that were almost eradicated (like measles and mumps) are increasing in incidence. I hope that this information helps you realize the importance of vaccines! I hope we, as a society and as a world, can erratic other diseases, like mumps or measles in the “near” future.
What Is Up With Polio Now?
Though polio was eradicated from the Western-Hemisphere it still remains a problem in other parts of the world like Asia and Africa. However, because of how effective the oral polio vaccine is it is very attainable to eradicated polio globally within the next couple of years. According to António Guterres, the United Nations Secretary General, it is a priority of the United Nations to help eradicate it globally. As of February 19th there have been a total of 12 cases of wild-type polio viruses (WPV) and 6 cases of circulating vaccine-derived poliovirus (cVDPV). I think that this is amazing because for this to be the amount globally, is very low and shows how it is very attainable to eradicated this globally within the next couple of years. All of theWPV cases and 3 of the 7 cVDPV cases came from Pakistan. With help from the UN, Pakistan is now making it a national goal to eradicate polio from their country by spreading awareness and availability of the vaccine.
I hope you all enjoyed this weeks blog. I think it is very important to know about polio because it shows how we can eradicate diseases with vaccines. I hope you now see how effective vaccines can be when the majority of the population uses them. I really hope and believe that polio can and will be eradicated within the next couple of years.
Thank you for reading this weeks blog and keep a look out for the next one!
Anna's Microbiology Blog 