Week 8.3: Hygiene and other personal interventions

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Do curso por The University of Hong Kong

Epidemics

23 classificações

The University of Hong Kong

Epidemics

23 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

In this part, I am going to talk about

the value of hygiene and other personal interventions.

The objectives of this session are: to identify

the modes of pathogen transmission that can be prevented

by hand hygiene and masks;

to describe a basic case-control study;

to discuss the role of hand hygiene and masks

in control of respiratory viruses.

Improvements in basic hygiene and sanitation

have played a major role in the reduction in burden

of infectious diseases in modern times.

For pathogens spread through the fecal-oral route,

like cholera and other diarrheal diseases,

improved hygiene can effectively prevent transmission

and control epidemics.

For respiratory pathogens that are typically spread

through contact and respiratory droplets,

simple interventions can also be effective

as we will see later in this part.

An important early figure in the application of hand hygiene

in medical settings was Ignaz Semmelweis,

a physician in Vienna in the 1840s.

In Semmelweis’ hospital,

doctors conducted autopsies in the early morning,

before attending the obstetric clinic.

Semmelweis theorized that decaying matter,

which he called cadaverous material contaminated

the hands of doctors who had recently conducted

autopsies on women who died from puerperal fever.

This matter was then brought into contact with women

who were about to deliver.

Semmelweis noted that mortality rates in his hospital

in Vienna were much higher than in Dublin,

since the advent of pathological anatomy in 1823.

He also noted that annual mortality rates

from puerperal fever were higher in the first clinic,

staffed by doctors, compared to the second clinic

which was staffed by midwives after 1842.

Semmelweis proposed and implemented an intensive

hand washing intervention in 1847,

and mortality rates immediately decreased.

You would have thought that Semmelweis would have been

feted for this important breakthrough,

but by challenging accepted medical practice he made

many enemies, perhaps not helped

by his difficult personality.

In a sad ending to this story,

he was forced out of the hospital in Vienna,

and died a few years later in a mental asylum.

The hospital reintroduced early morning autopsies,

and Semmelweis’ contribution was not fully recognized

until some years after his death when hand hygiene gradually

became accepted as a basic measure in infection control.

Surgical face masks were first introduced in surgery

more than 100 years ago, with the intention of protecting

patients from any bacteria shed from respiratory droplets

from the wearer's mouth and nose.

This is known as source control, because the idea is

to control the source of any potential infection.

Nowadays, surgical masks are often used for another reason,

as part of personal protective equipment,

to protect healthcare workers from infection

while treating patients with infectious diseases.

Other components of personal protective equipment

can include gowns, gloves, goggles, and face shields.

In 2003, a new coronavirus emerged which caused

a global epidemic of severe acute respiratory syndrome,

abbreviated as SARS.

One urgent question early in the SARS epidemic,

was about which infection control measures were necessary

to protect health care workers against infection.

A number of studies were conducted,

and I will discuss one such study

conducted by Dr. Seto and colleagues in Hong Kong.

The investigators conducted what is called

a 'case-control study'.

They identified 13 infected health care staff,

with documented exposure to SARS patients,

and interviewed them about the preventive measures

they had taken while they had cared for the specific

patients subsequently diagnosed with SARS,

whether or not SARS had been diagnosed at that time.

Two of the 13 staff reported wearing a face mask,

4 reported wearing gloves, none reported wearing a gown,

and 10 reported hand washing.

It is difficult to make any conclusion

based on this information alone,

what we need is a comparison group.

So the investigators also interviewed 241 non-infected staff

to get a better picture of the type of behaviours prevalent

in the hospital staff at that time.

This group is called a control group.

In the control group, all behaviours were

more commonly reported compared to the cases.

We can quantify the differences in various ways,

one of the most common is through odds ratios

which here we can interpret as risk ratios.

Significant differences between cases and controls were

identified for the use of face masks and hand washing,

and for all 4 measures combined.

The authors concluded that these basic infection control

measures, and particularly the use of face masks,

could adequately protect health care workers against SARS.

We can take a moment to think about the limitations

of this study, and other similar studies.

First, because the cases and controls

were interviewed about their past behaviours,

their responses might have been affected.

For example, cases might have been less likely to report

preventive measures since they know they were infected.

Second, the behaviours are correlated with each other,

and with other factors such as level of training

and experience and it is difficult to determine

which factors were most important in reducing

the risk of infection.

Nevertheless, this type of study can be done very cheaply

and easily, and can provide timely information

to guide infection control.

In addition to their importance in the hospital setting,

personal protective measures such as the use of face masks

and hand hygiene can also be used in the general community.

Widespread use of surgical face masks in the community

is a seminal image during emerging respiratory disease

epidemics and pandemics.

For example, in SARS in Hong Kong in 2003,

and in Mexico in 2009 at the start

of the swine flu pandemic.

However, the effectiveness of these measures in the

community is less certain, with controlled trials generally

identifying limited benefits of these measures.

Recent reviews of hand hygiene and face masks

against influenza found very modest benefits,

consistent with recent studies suggesting that

influenza viruses may sometimes spread through very fine

respiratory droplets, which can remain suspended in the air

for some time and can pass around

or even through face masks.

For emerging pathogens,

the effectiveness of these measures would depend on the way

in which they are spread and their transmissibility.

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