Poliomyelitis (Poliovirus)

Summary

Poliomyelitis, commonly known as polio, is a viral disease caused by the poliovirus, which can lead to paralysis. It spreads through person-to-person contact, primarily via the fecal-oral route. Major outbreaks in the past caused significant fatalities and paralysis, with a 1916 New York epidemic killing over 2,000 people. Polio can paralyze muscles required for breathing, leading to the use of iron lungs. Advances in science identified the virus as the cause, and vaccines (IPV and OPV) were developed. Polio has been eradicated in most countries, though cases remain in Pakistan and Afghanistan.

Takeaways

• 🦠 Polio is caused by the poliovirus, which can spread from person to person and infect the spinal cord, leading to paralysis.
• 📅 The first major polio outbreak in the U.S. was in 1894, resulting in 18 deaths and 132 cases of permanent paralysis.
• 🔬 Swedish scientist Ivar Wickman discovered in 1905 that polio is infectious and that not all cases are severe.
• 🧪 In 1908, scientists Karl Landsteiner and Erwin Popper confirmed that polio was caused by a virus, though the virus itself wasn't seen until the 1950s with the invention of the electron microscope.
• 🏥 A major polio epidemic in 1916 in New York City caused over 6,000 deaths across the U.S. and left thousands paralyzed.
• 🫁 The iron lung, developed in 1929, was a breakthrough for patients with paralytic polio, helping them breathe by using air pressure.
• 🧬 There are three serotypes of poliovirus (PV1, PV2, and PV3), and immunity to one serotype doesn't grant immunity to the others.
• 🚪 Poliovirus typically enters the body through the mouth via the fecal-oral route and infects the throat, intestinal tract, and bloodstream.
• 🧠 Around 1% of polio cases result in paralysis, where the virus invades motor neurons and destroys them, leading to poliomyelitis.
• 💉 The U.S. has been polio-free since 1979 due to successful vaccination programs, with two main vaccines available: the inactivated poliovirus vaccine (IPV) and the oral poliovirus vaccine (OPV).

Q & A

What causes poliomyelitis, commonly known as polio?

Poliomyelitis is caused by the poliovirus, which can spread from person to person and infect the spinal cord, leading to paralysis.

When was the first major documented polio outbreak in the United States, and what were its effects?

The first major polio outbreak in the U.S. occurred in June 1894, resulting in 18 deaths and 132 cases of permanent paralysis.

What important findings about polio did Swedish scientist Ivar Wickman publish in 1905?

Ivar Wickman discovered that polio is an infectious disease and that not everyone who contracts it develops a severe form.

Which scientists concluded that polio is caused by a virus, and when was this discovery made?

Karl Landsteiner and Erwin Popper concluded in 1908 that polio was caused by a virus, though the virus itself wasn’t visible until the 1950s with the invention of the electron microscope.

What was the impact of the 1916 polio epidemic in New York City?

The 1916 polio epidemic in New York City killed over 2,000 people in the city and around 6,000 nationwide, leaving thousands more paralyzed.

What is the iron lung, and why was it developed?

The iron lung, developed in 1929, is an artificial respirator used to help polio patients who experienced paralysis of the diaphragm and other muscles needed for breathing. It mechanically forced air into and out of the lungs.

How many serotypes of poliovirus are there, and why is this significant for immunity?

There are three serotypes of poliovirus: PV1, PV2, and PV3. Immunity to one serotype does not typically provide immunity to the others, which complicates efforts to prevent the disease.

What are the common modes of poliovirus transmission?

Poliovirus typically spreads through the fecal-oral route, entering the body through the mouth. It infects the throat and intestines before moving into the bloodstream.

What percentage of people infected with poliovirus experience symptoms, and how severe are these symptoms?

Over 70% of people infected with poliovirus do not show any symptoms. About 25% may experience flu-like symptoms, but only around 1% of cases result in paralysis or severe symptoms.

What treatments and prevention methods are available for poliovirus infections?

Polio is treated with supportive care, such as rest, fluids, and pain management. There are two types of vaccines for prevention: the inactivated poliovirus vaccine (IPV) and the oral poliovirus vaccine (OPV).

What is the current global status of polio, and which countries are still affected?

Polio has been largely eradicated globally, with the U.S. being polio-free since 1979. As of 2020, only Pakistan and Afghanistan still report cases of poliovirus type 1.