Polio: Infection, Symptoms, and History

• In 1921, poliomyelitis outbreaks occurred in America.
• Franklin Delano Roosevelt contracted polio after fighting a fire and swimming.

Polio Infection and Symptoms

• Polio enters the body through the nose or mouth and incubates in the intestines.
• Most patients are asymptomatic or experience flu-like symptoms such as headache, nausea, vomiting, and fever.
• Symptomatic or asymptomatic individuals can transmit the disease.
• Polio spreads through contact with infected feces or droplets in the air, food, or water.
• Once in the bloodstream, the patient produces antibodies.
• Around 10% of infected individuals develop symptoms, and 1% develop the paralytic form of polio. The disease is characterized by lifelong immunity against the virus.
• In paralytic cases, the virus reaches the brain and spinal cord, destroying nerve tissue.
• Spinal polio affects the limbs, while bulbar polio affects the cranial nerves and lungs.
• Paralytic polio has no cure, but physical therapy can help manage muscular paralysis symptoms.

Historical Context of Polio

• Before the 1900s, infants acquired immunity due to poor sanitation and exposure, with maternal antibodies providing protection.
• Improved sanitation paradoxically led to increased susceptibility in later childhood and adulthood.
• The March of Dimes, founded with President Roosevelt's help, funded polio research in the twentieth century.
• Polio is caused by three strains of stable viruses that are part of the enterovirus family, with RNA as their genetic material.
• Polio was a highly contagious disease that affected both rich and poor causing terrifying outbreaks until the early 1950s.

Jonas Salk and Polio Vaccine Development

• In 1947, Dr. Jonas Salk began researching poliovirus at the University of Pittsburgh.
• A method to grow poliovirus in cell culture was discovered in 1949.
• Salk developed a successful vaccine in 1952 using three types of virus grown in monkey kidney cultures and inactivated with formalin.
• Clinical trials began in 1954 in the United States and Canada.
• The vaccine was approved for distribution to children in 1955.
• The original Salk vaccine induced 260 cases of poliomyelitis, including 10 deaths but was soon corrected.
• Since it has been refined, Salk vaccine has a 70-90% protection rate is achieved.

Albert Sabin and the Oral Polio Vaccine

• In 1957, Albert Bruce Sabin tested a live, oral form of the vaccine with an attenuated virus.
• The Sabin vaccine became available in 1963.

Vaccine Administration and Safety

• The Salk vaccine involves two intramuscular injections one month apart, with boosters every 5 years.
• The Sabin vaccine is live and oral.
• The Salk vaccine is safe for those with compromised immune systems.
• Oral polio vaccine can also be given in three doses in the first two years of life, and a booster is given when the child starts school.

Advantages and Disadvantages of Live Vaccines

• Advantages of a live, oral vaccine are its long-lasting immunity, the prevention of reinfection of the digestive tract, and the lower cost of administering the vaccine orally.
• The disadvantage is that it cannot be used for patients with compromised immune systems.
• The Sabin oral vaccine is not suitable for those who have an enterovirus infection of the gastrointestinal tract.

Polio Eradication Efforts

• In 1960, there were 2,525 paralytic polio cases in the United States.
• By 1965, there were only 61.
• Between 1980 and 1990, cases averaged 8 per year, often induced by vaccination.
• There has been a single case by the wild virus since 1979.
• The Americas was declared polio-free in 1994.
• In 1988, the World Health Organization aimed to eradicate poliomyelitis from the entire world by the year 2000.
• Poliovirus is only found in humans, and polio is theoretically possible to eradicate since humans can be immunized.

Current Polio Vaccine Options

• Both the Salk and Sabin vaccines are effective alternatives used throughout the world.
• In the United States, the Sabin vaccine is used almost exclusively, whereas, in other countries, the Salk vaccine is preferred.
• Recombinant biotechnology and genetic alteration of the poliovirus are currently being researched.
• Scientists are using Escherichia coli to synthesize viral capsid proteins for vaccines.

An overview of poliomyelitis, including its outbreaks in America, how the virus enters the body, and the types of symptoms that can occur. It also touches upon the effects of the virus reaching the brain and spinal cord.