In an air-handling system that provides cooled air to occupants of a building, most of the air is returned from the space back to the air handler to be reused. This is called â¦ Return Air, or RA. However, some fresh air (called Outside Air, or OA) must be mixed in.
Polio is a viral infection that can cause permanent paralysis. The inactivated poliovirus vaccine (IPV) is usually given at ages 2 months, 4 months, 6â18 months, and 4â6 years. Though the oral poliovirus vaccine (OPV) is still used in many parts of the world, it has not been used in the United States since 2000.
There are two forms of polio: Minor poliomyelitis (also called abortive poliomyelitis) occurs primarily in young children, and is the more common of the two forms. The illness is mild, and the brain and spinal cord are not affected. Symptoms appear three to five days after exposure to the virus and include slight fever, headache, sore throat, vomiting, lack of appetite, and a general feeling of illness and discomfort. Major poliomyelitis is a more severe illness that develops approximately 7 to 14 days after exposure to the virus. Symptoms include fever, severe headache, stiff neck and back, and deep muscle pain. Some people experience temporary abnormalities of skin sensation.