Summary
Highlights
Dr. Mony Isai Mancilla introduces the topic of poliovirus, poliomyelitis, and polio vaccines. He explains that polio is caused by the poliovirus, an enterovirus, which usually causes mild symptoms but can lead to serious illness like poliomyelitis if it reaches the central nervous system. There are three serotypes of poliovirus (1, 2, and 3), and immunity to one offers minimal protection against the others, necessitating vaccination against all three.
Poliovirus is found only in humans and is primarily transmitted via the fecal-oral route, with some droplet transmission possible, especially during the first week of infection. Viral shedding in saliva and stools is reduced in individuals who have received the oral polio vaccine or had a wild polio infection. Polio is highly infectious, and silent transmission can occur, with active sharing of the virus through feces for 3-6 weeks. Only a small percentage (less than 5%) of infected individuals develop paralysis, with most being asymptomatic.
Symptoms, if present, usually appear after 10 days of exposure and can initially mimic a minor viral illness. Paralysis typically develops rapidly within 1-10 days, affecting one specific muscle group and progressing to complete immobility within 2-3 days. Key characteristics of polio-induced paralysis include fever, muscle pain, asymmetric and descending paralysis, and diminished deep tendon reflexes, while sensation remains intact. Diagnosis requires laboratory tests, such as poliovirus isolation from stool samples, as clinical presentation alone is insufficient.
Poliovirus can affect various parts of the body depending on where the infection settles. If it targets the spinal cord, spinal paralysis can occur, affecting limbs. If it affects the brainstem (bulbar and bulbospinal portions), it can impair breathing due to cranial nerve involvement. Polio-induced paralysis is permanent. The case fatality rate is 2-5% in children and significantly higher (15-30%) in adults. Currently, there is no cure for polio; treatment focuses on supportive management, including fever reduction, physical therapy, orthopedic management, and surgical intervention for deformities.
Two broad types of polio vaccines are available: Inactivated Poliovirus Vaccine (IPV) and Oral Poliovirus Vaccine (OPV). IPV contains inactivated forms of all three poliovirus serotypes, administered intramuscularly (0.5 mL per dose) at 14 weeks old (or 3.5 months) as per the Philippine National Immunization Program. IPV provides systemic immunity (antibodies in the blood) and is very safe with minimal local reactions. OPV, currently bivalent, provides both systemic and mucosal immunity (in the intestinal lining), offering protection against shedding and transmission, though there's a small risk of vaccine-derived polioviruses. Both vaccines are crucial for preventing polio and its spread.