Emerging Diseases Lecture 8: Polio 8.1: Overview 8.2: Incidence and Timeline 8.3: The Vaccine Race Salk Vaccine Sabin Vaccine 8.4: “Defeat” of Polio and the Age of Optimism

8.1: Overview: Polio is an Ancient Disease Poliomyelitis= polio Caused by a virus- named poliovirus Well-adapted to humans; Usually causes very mild disease Less than 1/1000 paralytic No other known hosts in nature

8.2: Disease Incidence Polio has been present since the days of ancient Egyptians but was not a serious problem until recently. As North America and Western Europe clean up their act in the late 19th and early 20th Centuries, incidence of most infectious diseases goes down. But the incidence of polio goes up!????????

8.2: Polio Timeline in US 1894: First US epidemic , in Vermont: 132 cases 1916: Major outbreak nationwide: 9000 cases in NYC alone 1934: 2500 cases in Los Angeles 1945-1949: at least 25,000 cases each year 1952: 58,000 cases 1953: 35,000 cases: “polio hysteria”-parents and children terrified of polio

8.2: Why So Many Cases? Disease very prevalent in human populations for many centuries. Historically-age of exposure to contaminated water was very young-usually led to a mild childhood disease only. Sanitation produces cleaner water. Delays age of first exposure. Severe symptoms more frequent in older individuals.

Vaccine for Polio? No cure for afflicted individuals May lead to permanent paralysis-total or partial Early attempts at vaccine in the 1930s went terribly wrong Scientists did not realize there were 3 strains of the virus in circulation By late 1930s National Foundation for Infantile Paralysis/March of Dimes led the vaccine campaign

March of Dimes 1940s-50s an effective ad campaign

Salk Vaccine 1948: Laboratory growth of poliovirus-use of cultured cells 1950’s: Vaccine “race” 1954: Large scale field trials of Salk (inactivated) vaccine-small scale tests on Pittsburgh schoolchildren 1955: April 12-successful vaccine announced 1955: The Cutter Incident-Cutter Laboratories produce contaminated Salk vaccine 1961: only 161 cases in US

Sabin Vaccine 1962: Sabin (attenuated) vaccine approved aka oral polio vaccine = OPV 1964: 121 cases in US

8.4: The “Defeat” of Polio A folk memory in US today Begins the “Age of Optimism”