Polio has killed and crippled humans for centuries, striking kids younger than 5 the hardest. The worst form of the ancient virus causes nerve injury that can lead to difficulty breathing, paralysis, and even death.
Polio, which often struck in warm summer months during 20th century epidemics, was one of the world's most feared diseases until Dr. Jonas Salk invented the polio vaccine and tested its safety back in 1954.
According to the US Centers for Disease Control and Prevention (CDC), before polio vaccines were available in the early 1950s, polio outbreaks caused more than 15,000 cases of paralysis each year in the United States. The World Health Organization (WHO) noted that reported cases of polio worldwide reached a peak of 350,000 by the year 1988.
One type of polio virus still circulates in the world
What causes polio is an enterovirus called the poliovirus. According to the Global Polio Eradication Initiative (GPEI), a WHO program, there are three strains of the poliovirus, two of which have been eliminated in the world.
One type of wild polio virus still circulates, however, in Afghanistan and Pakistan and can be picked up by travelers and carried worldwide. The CDC said that it takes only one traveler with polio to bring the disease back into the United States.
Transmission can also happen when not enough kids are vaccinated in an area. That typically transpires with the oral polio vaccine, which was created by Dr. Albert Sabin and first used in 1961. According to GPEI, this oral vaccine's formulation has a mixture of each of the three types of live attenuated poliovirus strains.
Once the said strain has infected an unvaccinated person, it begins to circulate and can be carried via travel by a person around the world. According to the New York State Department of Health, that may be a factor in the recent diagnosis of polio in a Rockland County, New York resident, the first case of polio reported in the United States since 2013.
What are the symptoms of polio?
According to the CDC, the poliovirus lives in an infected person's throat and intestines. People carrying the poliovirus, including those persons without symptoms, can spread the highly contagious virus for weeks in their feces. Viral transmission can occur via droplets from a sneeze or cough in rare cases.
Many cases of polio are asymptomatic like COVID-19. The CDC said people have no symptoms in about 95 percent of all polio cases. When symptoms appear, though, they can take three forms. Flu-like symptoms such as sore throat, nausea, headache, diarrhea, fever and fatigue are characteristics of abortive polio.
If those symptoms include additional neurological symptoms, such as a stiff neck or light sensitivity, the person may have nonparalytic polio. The WHO said that the most dangerous version of the poliovirus can cause paralysis within a matter of hours.
The said illness begins with flu-like symptoms, then transitions into spasms or muscle pain, and then loss of reflexes. Paralysis of one side or the other can soon follow, according to CNN.
