Week 8.1: Non-pharmaceutical interventions overview and John Snow

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Epidemics

29 classificações

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The University of Hong Kong

Epidemics

29 classificações

“If history is our guide, we can assume that the battle between the intellect and will of the human species and the extraordinary adaptability of microbes will be never-ending.” (1) Despite all the remarkable technological breakthroughs that we have made over the past few decades, the threat from infectious diseases has significantly accelerated. In this course, we will learn why this is the case by looking at the fundamental scientific principles underlying epidemics and the public health actions behind their prevention and control in the 21st century. This course covers the following four topics: 1. Origins of novel pathogens; 2. Analysis of the spread of infectious diseases; 3. Medical and public health countermeasures to prevent and control epidemics; 4. Panel discussions involving leading public health experts with deep frontline experiences to share their views on risk communication, crisis management, ethics and public trust in the context of infectious disease control. In addition to the original introductory sessions on epidemics, we revamped the course by adding: - new panel discussions with world-leading experts; and - supplementary modules on next generation informatics for combating epidemics. -------------------------------------------------------- (1) Fauci AS, Touchette NA, Folkers GK. Emerging Infectious Diseases: a 10-Year Perspective from the National Institute of Allergy and Infectious Diseases. Emerg Infect Dis 2005 Apr; 11(4):519-25. What you'll learn - Demonstrate knowledge of the origins, spread and control of infectious disease epidemics - Demonstrate understanding of the importance of effective communication about epidemics - Demonstrate understanding of key contemporary issues relating to epidemics from a global perspective

Na lição

Theme Three: Control (Non-pharmaceutical intervention (NPI))

Theme Three Summary

Week 8 Introduction1:42

Week 8.1: Non-pharmaceutical interventions overview and John Snow4:34

Week 8.2: Control of Cholera8:37

Week 8.3: Hygiene and other personal interventions6:23

Video 8.4: Isolation and quarantine and contact tracing6:02

Video 8.5: School closure7:49

Video 8.6: International measures including travel restrictions and entry screening4:40

Video 8.7: Zoonoses - market closure6:18

Conheça os instrutores

Gabriel M. Leung (HKU)
Dean
Li Ka Shing Faculty of Medicine
Joseph T. Wu (HKU)
Associate Professor
Li Ka Shing Faculty of Medicine
Kwok-Yung Yuen (HKU)
Professor
Li Ka Shing Faculty of Medicine
Tommy Lam (HKU)
Assistant Professor
Li Ka Shing Faculty of Medicine
Maria Huachen Zhu (HKU)
Associate Professor
Li Ka Shing Faculty of Medicine
Guan Yi (HKU)
Chair Professor
Li Ka Shing Faculty of Medicine
Benjamin Cowling (HKU)
Professor
Li Ka Shing Faculty of Medicine
Thomas Abraham (HKU)
Associate Professor
Journalism and Media Studies Centre
Mark Jit (LSHTM)
Professor
Department of Infectious Disease Epidemiology
Malik Peiris (HKU)
Chair Professor
Li Ka Shing Faculty of Medicine
Marc Lipsitch (Harvard)
Professor
Department of Epidemiology

Non-pharmaceutical interventions,

sometimes abbreviated as NPIs, are actions,

apart from getting vaccinated and taking medicine,

that people and communities can take to help slow

the spread of infectious diseases and control epidemics.

This week, we are going to look at a range of NPIs

that can be used to mitigate the impact

of an epidemic of an emerging infectious disease.

The objectives of this first part are:

to identify the date of the first global pandemic of cholera;

to define the incubation period of cholera;

to have defined the case fatality risk of untreated cholera;

and to discuss the two competing hypotheses

about the mode of communication of cholera

in the mid 19th century.

To start, I want to go back to

the foundations of the science of epidemiology,

and one of the best-known non-pharmaceutical interventions

among infectious disease epidemiologists.

This is the story of John Snow,

cholera, and the Broad Street pump.

John Snow was born in 1813 into a poor family

in the North of England.

At the age of 14, he was apprenticed to a surgeon,

and at the age of 23, he travelled to London,

to continue his training.

He soon qualified as a surgeon, a general practitioner,

and later as a physician.

He began to experiment with anesthetics in the mid 1840s,

and played a major role in the standardization

of the use of anaesthetics,

both in terms of the preparation and delivery

of the anaesthetic vapors,

and in the monitoring of the patient during anaesthesia.

He excelled in obstetrics,

and became so well known that Queen Victoria

invited him to administer anaesthesia to her

during the birth of two of her children in the 1850s.

Not only was he an accomplished physician,

he was also an active scientist,

taking time off from his medical practice

to study various tropical diseases.

Cholera is a diarrheal disease

caused by the bacterium Vibrio cholerae.

In infected persons, disease appears

after an incubation period of 1-3 days.

Without appropriate treatment,

which is basically rehydration,

severe cholera kills about half of affected individuals.

While cholera is thought to have been prevalent

in the Indian subcontinent for hundreds,

or even thousands of years,

it did not spread to the rest of the world

until the early 19th century.

The first global pandemic started in the early 19th century,

reaching Europe by the late 1820s.

Further pandemics occurred sporadically

through the 19th century,

killing tens of millions of people

worldwide in that century.

John Snow first encountered cholera at the age of 18,

during his apprenticeship.

Cholera returned in a second pandemic in the late 1840s,

when Snow was practicing physician in London.

At the time, the predominant view of cholera

was that it was spread by “miasma”, or “bad air”.

An analysis that supported this view

was published by William Farr,

a famous demographer and statistician.

Farr studied the incidence rates of cholera

in persons living at different elevations above sea level,

and observed that the risk of cholera

appeared to be higher in persons living close to sea level,

or equivalently closest to the river Thames,

where there was more organic matter

that produced noxious gases.

John Snow took a different view.

He was an expert in the behavior of gases,

through his work on anaesthetics,

and he didn’t think that the miasma theory

explained the epidemiology of cholera.

In 1849, he proposed an alternative hypothesis,

that cholera was a contagious disease

acquired through the fecal-oral route,

and spread by contaminated water, not through the air.

He noted that cholera was a disease

of the intestines, not the lungs,

pointing to infection via the alimentary canal,

rather than the respiratory tract,

and he drew an analogy with intestinal worms.

Snow noted that cholera thrived in places

and subpopulations with poorer hygiene,

and suggested that emptying sewage into waterways

could contribute to the dissemination of the disease.

This was controversial,

because proponents of the miasma theory

supported the disposal of sewage into the river

to reduce the bad smells around cesspits.

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