Case Study VI: History and Epidemiology of Polio Epidemics

Case Study VI: History and Epidemiology of Polio Epidemics

Rural Observations

• Severity of Cases in Rural Areas

Epidemiological Questions

Overview of Poliomyelitis

Key Epidemiological Points

• How did it spread among the community?
• How were people infected?
• How did it spread through the body?
• How is it eliminated?

• Case definition
• Communicability
• Acquired immunity
• Incubation period

• Enterovirus of the Picornavirus group
• Types
• Type I (Paralytic)
• Type II (Non-paralytic)
• Type III (Bulbar)
• Transmission
• Fecal-Oral
• Pharyngeal-Oropharengeal
• Symptoms
• Flu/Cold like
• Risk
• Underdeveloped populations
• Unvaccinated populations
• Vaccine
• Salk
• Sabin

Epidemic Curve

Case Study Questions, cont.

Introduction

Ivar Wickman

• When was the poliovirus discovered?
• What were Wickman's contributions to the study of polio?
• What did Medin do?
• Why is polio more prevalent in rural areas than in urban?
• What is the most common type of polio?
• What are the two phases of polio?

• Pupil of Medin
• Recognized that there were 3 types of polio: paralytic, non-paralytic, and bulbar
• Recognized that non-paralytic polio occurred in 99% of all polio infections.

Names of Polio

• late 1700's - Debility of the lower extremities
• mid 1800's - morning paralysis
• 1850's-1900s - Heine-Medin
• Anterior Poliomyelitis
• Infantile Paralysis

• Difficult disease to understand at first due to its' nature.
• Real breakthrough was in it was discovered to be biphasic
• 1st phase: symptoms similar to a cold
• 2nd Phase: virus moves to the CNS and causes paralysis

Karl Oskar Medin

Polio Virus Discovered

• Swedish physician
• First to compile a comprehensive set of clinical features
• Outbreak of 1887

Case Study Questions

First Polio Epidemiological Studies

• 1908 in Vienna by Karl Landsteiner and E. Popper
• 1911, Carl Kling obtained tissue samples from deceased bodies.

• Identify the pathogenic agent and the group to which the infantile paralysis belongs.
• Identify the location in which this pathogen is harbored.
• Identify the mode of transmission and related epidemiological implications.
• Discuss and explain the issues of age and its implications for the epidemiology of polio and infantile paralysis.
• Why did physicians and epidemiologists have such a difficult time identifying outbreaks and the spread of polio?

Age Issues: Not just a child's disease

• Any age can be affected
• Children <5 are especially vulnerable
• Why?

• What were the epidemiological limitations of Flexner's work on polio?
• Who was Dr. Frost, and what were his contributions to epidemiological investigations of infantile paralysis/polio?
• How did Dr. Frost contribute in the way of understanding modes of disease transmission in poliomyelitis?
• Which specific methods and approaches was Dr. Frost able to use and establish as solid epidemiological methodology?

• What unique epidemiological observations and contributions about the epidemic of infantile paralysis were made by Dr. Caverly from his experience in rural Vermont?
• What epidemiological observations did he make regarding the age of victims and polio epidemics?
• What were some critical thinking and observational errors made regarding epidemiology that were made by Dr. Caverly?

• By 1934, a great deal was known about poliomyelitis. Summarize all that was known about the epidemiology of polio.
• How serious was the polio epidemic of 1934. What were the social, psychological, and political implications and their effects on the epidemiology of polio surrounding this case?
• What were the final conclusions of the LA 1934 epidemic and what were the implications for the future?