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Author: bacterina

What is Polio?

Your absolute favorite AP Biology blogger, Bacterina, is releasing a 3 part Special Edition feature about the Poliovirus. Prepare to be amazed and intrigued about the deadly disease of Polio and the incredibly effective Polio vaccine. 


Both an article on the historical significance of Polio and another on the Polio vaccines allow us to see the background of Polio.Poliomyelitis or Polio as it is commonly known has existed in the world for 6000 years. Researchers know this from the discovery of Egyptian mummies with withered limbs. The disease is a life-threatening disease caused by the poliovirus. More recently Polio was an epidemic in the 20th century in the US and over the world occurring mainly in the 1940s and 1950s. But in the 1950s a vaccine was created and the rates started to decrease. Since May of 1988, the World Health Assembly strives to eradicate poliomyelitis and because of this, the cases of Polio have decreased by 99%. Now the World Health Organization has declared the regions of the Americas, Western Pacific, and Europe as polio-free. On the other hand, South-East Asia is not free of polio but is working to eradicate the disease. The most well-known case of Polio was when President Franklin Delano Roosevelt was paralyzed by Polio and remained in a wheelchair for most of his adult life. The President was only in his late 30s when he got polio. Most people who are paralyzed by Polio were confined to wheelchairs or iron lungs for the rest of their adult lives. 

A Child Infected with Paralytic Polio

A very informative article written by the CDC informs us of the symptoms of Polio, how it is transmitted, and how to prevent the disease. The articles share the information which is explained below. 


Initially, individuals infected with Polio experience flu-like symptoms where they have a sore throat, fever, nausea, fatigue, headache. These symptoms last for 2 to 5 days and eventually go away. A smaller amount of people infected with polio will have more serious symptoms like paraesthesia, Meningitis, or Paralysis commonly in the legs, arms, or both (.5 percent of people will experience this). Of those who have paralysis, 2/100 will die from the paralysis because the virus will paralyze key muscles that allow ourselves to breathe. Only people who have paralytic disease polio are considered to have poliomyelitis. 


Poliovirus is a very contagious disease and lives in an infected person’s throat and intestines. It is spread through person to person contact by either fecal matter or from droplets of a sneeze or cough (less common). A person can be infected with polio if they have feces on their hands or on other objects that eventually enter their mouths. After someone is infected they can spread the virus to other people from immediately to two weeks. The virus can infect others if it contaminates food and water that is later ingested. 


There are two vaccines that act as preventative measures against this disease. The inactivated poliovirus vaccine (IPV) is given by an injection into a patient’s arm or leg depending on their age. In the United States, this vaccine has been used widely since 2000. The other type of vaccine is an Oral poliovirus vaccine which is used all over the world. Many children who get the vaccine are protected from the disease with a success rate of 99 percent. There is currently no cure for poliovirus but there are ways to speed up recoveries like bed rest, pain medications, and a ventilator.

Types of Polio Vaccines Available and How They Work

According to a very informative article by the Children’s Hospital of Philadelphia, there are two types of Polio Vaccines. Below we look at the specifics of these two vaccines.  

What types of Polio Vaccines are available? 

There are two types of Polio Vaccines the inactivated polio vaccine (IPV) and the oral polio vaccine (OPV). The IPV was made first in 1955 and is administered by a shot. The OPV which was made in 1961 is more convenient and is given by liquid form. These vaccines have been incredibly effective and have eradicated Polio in the US since 1979 and the Western Hemisphere since 1991. IPV is the only polio vaccine that is used in the US. 

How Were the Vaccines Made Initially?

Oral Polio Vaccine

The OPV was created from weakening three strains of the poliovirus that caused the disease by growing these strains in monkey kidney cells. Because this was growing the kidney cells the virus was able to be weakened where if ingested it would create an immune response that didn’t cause the disease. The OPV allows the body to have a first defense against the disease because the induced antibodies are in the intestines. But OPV rarely went back to the natural form which eventually caused paralysis. 

Inactivated Polio Vaccine 

The IPV, unlike the OPV, could not reproduce by itself which means that it does not have the capability to revert back to its natural form. In order to make IPV, the poliovirus is purified and killed with formaldehyde. Also unlike the oral vaccine, the IPV does not create antibodies in the intestines but rather in the bloodstream. This prevents the virus from traveling through the blood into the brain or spinal cord which then disables paralysis. 

Why does the US use only the Inactivated Polio Vaccine?

We only use the Inactivated Polio Vaccine instead of the Oral Polio Vaccine because the IPV cannot replicate which means it will never revert back to the natural form and cause paralysis. Now every infant in the US is required to have four doses of the shot. On the other hand countries outside of the US still use the oral version because it is more affordable and easier to give which allows more people to receive the vaccine.

Polio vaccine dropped on to sugar lump for a child patient

How Poliovirus Infects Our Bodies

How polio Initially affects your body – 

According to an informative article by Khan Academy, Poliovirus typically enters the body through the nose and the mouth and will immediately start to infect the cells of the lining of the larynx. The virus will then travel to the intestines where it will begin to reproduce rapidly. After a week of being infected the virus will start to spread to your tonsils and other parts of the immune system. Gradually the poliovirus will break into the bloodstream where it then can be transported around your body. Most of the time the virus will be eradicated in the bloodstream or in the intestines but in some people, it can infect the Central Nervous System. If it reaches the CNS it will begin to replicate inside of the motor neurons and copy itself thousands of times. Then when it is ready it will kill the neurons and spread to even more uninfected cells. The disease will then fall into three classifications depending on where the neuronal damage is occurring. 

two children polio-stricken children attending physical therapy circa 1963

Three classifications of Polio

Spinal Polio 

This is the classification when the poliovirus kills the motor neurons in the gray matter of the ventral horn of the spinal column. As the cells in the region are dying off the muscles of the limbs are not able to receive signals from the CNS so they begin to atrophy and become weak. In a few days, the patient will be fully paralyzed. This is the most common form of polio. 

Bulbar polio 

This form of polio is not as common as spinal polio. It is classified by this when the poliovirus infects and kills neurons in the bulbar region of the brain stem. This affects the muscles we use to speak, swallow, and breathe. 

Bulbospinal Polio

About 20 percent of people will get bulbospinal polio where they have both bulbar and spinal infection. In this situation poliovirus infects the upper part of the cervical spinal cord making the diaphragm paralyzed.   


Structure of Polio –     

An article by Science Direct and the American Society for Microbiology explains the structure of Poliovirus. Poliovirus is characterized as a nonenveloped virus and is composed of an RNA genome and a protein capsid. The genome is a single-stranded RNA genome and is 7500 nucleotides long. The shape of the virus is an icosahedral capsid and it belongs to the Picornaviridae family. Because poliovirus is a nonenveloped they don’t follow the same pathways as enveloped viruses take. Usually, with an enveloped virus the virus will deliver nucleocapsids to the cytoplasm of cells and fuse with the viral membrane with the host cell membrane. Instead, nonenveloped viruses will need to travel within the organelle membranes and infect specific cellular structures that would support the arrival of a virus to the cytosol. This is made possible when the virus penetrates across the endomembrane of the host cell which allows the virus to infect the cell. 

Type 3 poliovirus capsid, colored per chains

Climate Change Killing the Environment Part 1000000 – How Ocean Acidification is Damaging Shark Scales

What is Ocean Acidification and How Does it Affect Sea Life?

During Climate Change the amount of carbon dioxide (CO2) in the atmosphere increases which also increases the amount of CO2 in the ocean. This CO2 which dissolves in the ocean combines with water to create carbonic acid. This added acid lowers the pH of the water which therefore acidifies the seawater. When the pH is lowered, the acid harms organisms like coral or other calcium-based structures because the acid starts to break down their calcium. 

Coral Facing the Effects of Ocean Acidification in the Great Barrier Reef

How Does This Affect the Sharks? 

If you look closely at most fish you will see that they have flat scales but Sharks, on the other hand, have scales that resemble teeth and are called denticles. Unlike other fish, Shark denticles cover their entire bodies and influence the way they swim. The denticles on Sharks are also made up of compounds containing calcium which is sensitive to a lower pH. Sadly because of this Sharks like corals will suffer from the effects of Ocean Acidification.  

Shark Denticles under a Microscope

The Study 

The article by the Heinrich-Heine University Dusseldorf focuses on the study which was performed by the research team from two South African research institutions the University of Duisburg-Essen and Heinrich-Heine University. They studied both puffadder shysharks who live on the bottom of the Atlantic Ocean off the coast of Cape Town and ones who lived in the DAFF Research Aquarium in Cape Town. For several weeks the researchers kept one group of sharks in a controlled seawater environment and another group in acidic water. After this time the researchers compared the denticles of these two groups and noticed that on average about 25% of the acidic water shark’s denticles had been damaged while in the controlled group the percentage was less than 10%. The acidic group’s denticles were damaged where it affected their ability to swim. Furthermore, Shark’s teeth are made of a similar compound to their denticles so the acidity also affected their food intake. 

Puffadder Shyshark on the bottom of the ocean floor

How Are Sharks Combatting 

Researchers continued their study and analyzed the blood of the animals in the acidic and normal environments. They discovered that the blood of sharks in the acidic environments had higher concentrations of both CO2 and bicarbonate. Interestingly, as sharks have more bi-carbonate in their blood this prevents the blood from becoming too acidic. This shows that sharks have acid-base regulatory processes for adapting to environmental changes. Although Sharks have a way to combat these changes not all animals have ways to protect themselves. So as more climate changes issues happen it is vital that we as humans are aware of the harm and strive to find ways to reserve its effects. 

Microbes Role in Evolution

In the human body, there are trillions of bacteria that come together to make a collective group called microbiomes. These cells are an essential part of the human body and regulate our risks to get obesity, asthma, and allergies. Considering microbials help our bodies function, researchers then are wondering if microbials have played a critical role in our evolution. In an article by Carrie Arnold a writer at Scientific American, she illustrates microbiome’s effect on evolution through two studies on insects.

Microbiome’s Effect on Mate Selection

Eugene Rosenberg of Tel Aviv University conducted an experiment in 2019 which found that raising fruit flies on different diets changed their mate selection. During this experiment, the fruit flies would choose to mate with flies with the same diet as them. The flies would revert back to there original mating patterns after they were given antibiotics. The results showed that the changes in the gut microbes from the diet caused the flies to change their choice of mate.

Microbiome’s Effect on Longevity and Ability to Reproduce

In 2011 Geneticist Seth Borderstein at Vanderbilt University conducted an experiment with two types of termites – Zootermopsis angusticollis and Reticulitermes flavipes – to test an organism’s life span and their ability to make offspring. The study found that after the study the antibiotic fed termites had less of a variety of gut bacteria and fewer offspring. The lead researcher Borderstein then concluded that there were important microbes reduced by the antibiotics. Because microbes help with digestion and the absorption of nutrients this reduction left the termites malnourished thus producing fewer eggs.


These two studies help to illustrate that researchers can no longer see a separation between an organism’s genes and their microbiomes. They both work together in a single hologenome. One of the researchers, Rosenberg, says that by looking at the history of botany and zoology we can see how billions of microorganisms are connected to most animals and plants. Scientists have to look at hologenome in order to understand an organism. Microbiomes are also important in human evolution too. This is shown through human adaptations of digestion, smell, and the immune system. Borderstein says that these changes over time are very likely to be a product of microbiomes in the body. Bordenstein ultimately argues “the microbiota are as important as genes.”

3-D Printing’s Role in the Future of Organ Transplants

According to the statistics provided by the Health Resource and Service Administration’s article on Organ Donation , every day there are over 16,000 people waiting on the organ transplant list while only 80 of those people actually receive the transplants. Although we have many people in the world because of the donor requirements set by UNOS (United Network for Organ Sharing) , the same blood type, same organ size, matching of the donor and recipient immune system and if the recipient is a child or adult, there is a small number of donors who are eligible for donation. 3D printing potentially could fix the issue of matching organ donations. 

Described in an article by Amy Norton a HealthDay Reporter from US News and World Report, 3D printing is the process of a computer creating three-dimensional objects by layering varying materials. Researchers have developed ways to use 3D printing in order to create customs tissues and organs for patients, a process called “bioprinting”. The problem with creating tissues to work cohesively within the human body is that those tissues need to connect with blood vessels and nerves flawlessly. Credit: Paige Derr and Kristy Derr, NCATS

Although a fully functioning bioprinted organ is years away researchers at Carnegie Mellon University in Pittsburgh are working to create ways to make artificial and working tissue in humans. At Carnegie Mellon University, Lead researcher Andrew Lee and his team have formulated a new method of bioprinting, called “FRESH 2”, which uses collagen in order to create parts for the human heart. Collage, a plentiful protein in the body that is also vital to the construction of the extracellular matrix illustrates the challenges with printing cells and soft living materials. If collagen was printed by itself the result would be a puddle. But within this study, the researchers supported the collagen with a gel to allow it to solidify. The process allows them to manipulated collagen into any shape or form they want and furthermore helps them to understand how to shape living cells in general. The researchers also used collagen and human heart muscles as “bio-ink” in order to create a small model of the heart’s left ventricle, the main pumping chamber. After a couple of days, the artificial chamber had the ability to contract.

Although right now there is a perfect process for artificially created organs the works of the researchers represent a significant stepping stone in the process of bioprinting. With the research artificial tissues and cells comes the hope that one-day 3D bioprinting can create custom tissues for patients and save countless lives.


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