Polio, or poliomyelitis, is a viral infection that can be acute and potentially destructive. Humans are the sole natural carriers of the poliovirus. The virus enters through the mouth, replicating in the throat and intestines. Some of the virus then enters the bloodstream, spreading to other areas where it multiplies more extensively. Another wave of viremia (presence of the virus in the blood) leads to the virus attacking the central nervous system (CNS), particularly targeting the spinal cord and brain.Infections in the CNS cause inflammation, especially affecting the anterior horn cells of the spinal cord and the brainstem, which is the connecting structure between the brain and spinal cord. Polio often presents as a mild illness in 80% to 90% of cases, particularly in young children, without affecting the CNS. Symptoms include mild fever, headaches, and vomiting occurring 3-5 days after exposure, with recovery within 24-72 hours. This mild form is known as abortive polio.In more severe forms, polio can be either non-paralytic or paralytic. Symptoms usually appear 7-14 days after exposure without prior illness, particularly in older children and adults. These symptoms include fever, severe headaches, neck and back stiffness, deep muscle pain, and sometimes hypersensitivity or altered sensations. In some cases, this viral infection doesn't progress further, but in others, it leads to the loss of reflexes and muscle weakness or paralysis.Recovery is usually complete in abortive and non-paralytic polio forms. In cases of paralytic polio, about half of the patients recover fully, around 25% experience mild disabilities, and the remaining suffer from severe permanent disabilities. Most muscle function recovery occurs within the first six months, but some improvements can continue for up to two years. Rehabilitation is crucial during recovery from paralytic polio. Prevention through vaccination remains the most effective approach. The global fight against polio has been largely successful, with the disease remaining only in Pakistan, Afghanistan, Nigeria, Somalia, and Kenya as of June 2013.U.S. President Franklin D. Roosevelt, a polio survivor, collaborated with the National Foundation/March of Dimes to raise funds against this once-dreaded disease. Polio is also referred to as infantile paralysis.
