Striking children younger than 5 the hardest, the worst form of the virus causes nerve injury that can lead to paralysis, difficulty breathing and death. During 20th century epidemics, the virus often struck in warm summer months, sweeping through towns and cities every year or so.
Polio was one of the world’s most feared diseases until Dr. Jonas Salk invented the polio vaccine and tested its safety in 1954.
What causes polio?
One type of wild polio virus still circulates in Pakistan and Afghanistan, however, and can be picked up by travelers and carried worldwide. “It takes only one traveler with polio to bring the disease into the United States,” the CDC said.
Transmission can also occur when not enough children are vaccinated in an area. That typically occurs with the oral polio vaccine, created by Dr. Albert Sabin and first used in 1961. This vaccine’s formulation has a mixture of each of the three types of live attenuated poliovirus strains, according to GPEI.
“The weakened strains are shed by vaccinated children into the environment via their digestive systems and can pass from one unvaccinated individual to another, a process exacerbated by poor sanitation systems and the absence of clean drinking water,” the GPEI said.
Once the strain has infected an unvaccinated person, it begins to circulate and can be carried via travel around the world.
“This suggests that the virus may have originated in a location outside of the U.S. where OPV is administered, since (reverted) strains cannot emerge from inactivated vaccines,” the statement said.
Polio is highly contagious
Most people come into contact with polio by picking up a tiny piece of infected poop and then touching the mouth. Exposure to the virus also occurs when children mouth toys or other objects contaminated with feces.
In unsanitary conditions, the virus can also spread via contaminated food and water.
Symptoms of polio start like the flu
Like Covid-19, many cases of polio are asymptomatic. In fact, people have no symptoms in about 95% of all polio cases, the CDC said.
When symptoms appear, they can take three forms. Flu-like symptoms such as headache, sore throat, nausea, diarrhea, fever and fatigue are characteristics of abortive polio.
If those symptoms include additional neurological symptoms, such as light sensitivity or a stiff neck, the person may have nonparalytic polio.
The most dangerous version of polio can cause paralysis within “a matter of hours,” the WHO said. The illness begins with flu-like symptoms, then transitions into muscle pain or spasms, and loss of reflexes. Paralysis of one side or the other can follow.
Treatment for polio
There is no cure for polio, only treatment to alleviate the symptoms.
“Heat and physical therapy (are) used to stimulate the muscles and antispasmodic drugs are given to relax the muscles,” the GPEI said. “While this can improve mobility, it cannot reverse permanent polio paralysis.”
Vaccination is the only prevention.
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