Disease Control

Disease control means the measures a government or health service takes to reduce the spread of an infectious disease through a whole population, rather than protecting one person.Key public health measures include:• Surveillance: monitoring the number and location of cases, so outbreaks are spotted early. Some diseases, such as measles, are notifiable: doctors must report every case.
• Isolation of people who are ill, and quarantine of people who may have been exposed but are not yet ill, for the length of the incubation period.
• Contact tracing: finding and testing or isolating everyone an infected person has been in contact with.
• Travel restrictions and screening at borders.
• Vaccination programmes aimed at reaching herd immunity, and ring vaccination of contacts around each case.
• Culling of infected animals, e.g. in foot-and-mouth disease or bird flu.For vaccination, the proportion of the population that must be immune to stop the disease spreading is the herd immunity threshold:threshold = 1 − 1/R₀Worked example. For a virus with R₀ = 4, the threshold is 1 − 1/4 = 0.75, so 75% of the population must be immune. For measles (R₀ about 15) the threshold is about 93 to 95%, so very high vaccine uptake is needed.These measures together can eradicate a disease. Smallpox was declared eradicated in 1980 after a worldwide programme of surveillance and ring vaccination. It was possible because smallpox had no animal host, caused obvious symptoms, and its vaccine was stable and effective.