Recent Posts

swiss cheese slices with a family and covid 19 virus image
Posted in #covid-19

Swiss Cheese Model for COVID-19

The Swiss Cheese Model for COVID 19 is an excellent mental tool to visualize COVID 19 prevention strategies.

First, about the Swiss Cheese Model. As emphasized by James Reason, the model’s creator, it invites us to look at a human error as a consequence, not as the cause. Therefore, according to this line of thinking, error is not a moral problem but a system problem. I have discussed it in the above post.

Swiss Cheese Model for COVID 19

We can apply the Swiss Cheese Model for COVID 19 to visualize and understand COVID 19 prevention strategies. In fact, academics and healthcare practitioners have already applied the model for this purpose. I will discuss their versions here.

Swiss cheese layers with a family and COVID 19 virus
Apply the model for COVID 19

The above image depicts my version. It features the following characteristics.

1. COVID 19 defense layers arranged in levels

The prevention strategies are categorized into three levels: Micro, Meso, and Macro. I bring this group nomenclature from the sociological literature. The following list clarifies what those terms refer to.

  • Micro-level: Individual-level
  • Meso – level: Group or community level
  • Macro-level: Political/policy level

2. The levels in a hierarchical order

The levels are arranged in a hierarchical order. The macro-level layers yield the highest impact. The meso and micro-level layers follow each other respectively. The slices’ increase in size from micro to macro represents it.

3. Each level includes at least two defense layers (slices).

Each level includes at least two layers or strategies (two cheese slices). This is not comprehensive and requires modifications. These layers carry holes of varying sizes and shapes. The holes shift their positions and hence they are dynamic.

  • Micro-level defense layers: Stay at home, face mask, and physical distancing
  • Meso – level defense layers: Community support and lockdowns
  • Macro-level defense layers: Paid sick leave and border control

4. The lower level is dependent upon the adjacent higher level.

Any level cannot withstand by itself; each layer is dependent on its adjacent one. The image depicts it.

The above list of prevention strategies is not complete, and the model deliberately omitted vaccine and testing because its aim is to highlight the relative importance of standard preventive measures. Those interested can include any other measure.

Previous models

Few Swiss Cheese models for COVID 19 exist. The most popular one is the version of Ian Mackay, a virologist from Brisbane, Australia. The New York Times reported it after his version went viral through Twitter. The following is his version.

Ian Mackay’s Twitter on the model

I found a Sinhala version of the Ian Mackay’s version of the Swiss Cheese Model.

File:SwissCheese ver3 SINHALESE.jpg

A Sinhala version of Ian M. Mackay’s adaptation through Wikimedia Commons under the license of CC BY 4.0.

The New Zealand version

Siouxsie Wiles, Associate Professor at the University of Auckland with Toby Morris introduced the following model. It is a very comprehensive one as you can see it. You can read about it in this post of COVID 19 nad Swiss cheese system.


Swiss cheese model for COVID 19 prevention

Source:; New Zealand’s Swiss Cheese model for COVID 19 under the license of CC BY-SA 4.0

A yellow colored slice of Emmental Swiss cheese
Posted in mental models

Swiss Cheese Model and the Hot Cheese Model

The Swiss Cheese Model and the Hot Cheese Model revolutionize the way we traditionally think of human error. In short, both models force us to move away from “blaming someone” for human error; instead, it pushes us to look at human error as a consequence, not as a cause. In fact, the Hot Cheese Model is an improvement to the classic Swiss Cheese Model.

About Swiss cheese

Following is a special type of Swiss cheese slice. It has holes in it. Among many, this is only one variety of Swiss cheese. This variety is from the Emmental area of Switzerland and also known as Alpine cheese. It is yellow, medium-hard, and therefore not flexible.

A yellow colored slice of Emmental Swiss cheese

A slice of Emmental Swiss cheese

Source: Emmental Swiss Cheese Slice; National Cancer Institute; Renee Comet (photographer): Wikimedia Commons on the public domain

About the Swiss Cheese Model

In 2000, James Reason, a professor in Psychology at the University of Manchester introduced this model. He published it in British Medical Journal under the title, “human error: models and management”. This is a “mental model” that helps us to visualize human errors in healthcare through a “system lens” instead of a “moral lens”. As a result, it forces us to move away from the emotional trap of the “blame game”.

James Reason’s Swiss Cheese model: Source: BMJ 2000 March 18.

This is one of my favorite conceptual models that helps to discuss behavior change options without prejudice. I have used it before as a community physician at a private hospital’s family and corporate health program in Sri Lanka in 2014 after my retirement from the government service.

Swiss Cheese Model in patient safety

Swiss Cheese Model in patient safety newsletter

Following are the James Reason’s thoughts about it;

Do not see human error as a moral problem

Think of deaths due to COVID-19. We, particularly those who hold authority, can easily find faults with the “general public” for not adhering to the recommendations; on the other hand, others can find faults with health officials, decision-makers, and politicians. We always fall into this trap of making it personal because blaming someone is emotionally satisfying.

Blaming individuals is emotionally more satisfying than targeting institutions.

James reason; “hUman error: models and management”, 2000, British medical journal

Instead, look at human error as a consequence, not as a cause.

James Reason conceptualizes that “humans are fallible and errors are to be expected even in the best organization system”. As a result, we need to see human errors as consequences, not as causes. In this paradigm shift, we do not have any room for the blame – game. In other words, this is an “upstream” journey; those who hold power cannot pass the ball down. Everyone has to bear equal responsibility and accountability.

This is the basic premise of this system approach. In fact, the systems approach forces us to think of humans as only a cog of a larger wheel of systems. So, here a human error is not seen as a failure but a variability. The focus is on the conditions or environments under which they operate or behave.

Swiss cheese model’s systems approach

James visualizes this system approach in layers: Some are engineered such as alarms, physical barriers, and automatic shutdowns, etc; others are human barriers such as physicians, pilots, control room operators in the aviation industry. Procedures and admin controls are other layers.

Ideally, any layer should not have holes; but in reality, there are many. And, the holes are dynamic; it constantly changes in size, shape, and shifts locations. Having holes in one or a few layers does not necessarily result in bad outcomes or disasters. Instead holes in each layer need to be aligned together for a disaster to happen. When a disaster occurs, according to the model, one cannot look at only one layer; we need to examine all the layers to prevent it from happening again.

Active failures and Latent failures

He grouped the holes into two:

  • Active failures
  • Latent

The active “holes” consist of slips, lapses, fumbles, mistakes, and procedural violations. For example, administering the wrong drug is an active failure.

The Latent ones are the “holes” in the management decisions that lead to understaffing, time pressure, lack of facilities, unworkable procedures, etc. As its name suggests the latent conditions lie dormant years in the system. He used another analogy here; active holes are like mosquitoes; although we can remove them one by one they keep coming. The Latent ones refer to the breeding places we can remove.

However, this model contain several limitations.

Hot Cheese Model: An improved Swiss Cheese Model

Li Y and Thimbleby H. in 2014 introduced several improvements to the James’ Swiss Cheese Model and named it has the Hot Cheese Model. This model addresses the limitations of the classic model. As the name implies, this Hot Cheese Model is hot, fragile, flexible, and new holes can form with time. in contrast to the classic model, this model emphasizes that adding more layers does not necessarily bring more protection. It might add new holes to the system.

A comparison between the classic Swiss Cheese Model and the Hot Cheese Model

Following are the key differences between the classic Swiss Cheese Model and the Hot Cheese Model.

  • The original model sees managerial, policy, and procedural actions as latent ones. The Hot Cheese Model argues these layers are also active, not latent.
  • The original model implies more layers minimize the chances of error. The Hot Cheese Model argues more layers can also introduce more errors (drips) in addition to the errors that pass through from previous layers.
  • The original model does not accommodate the shape-changing nature of a loophole. The Hot Cheese Model recognizes the hole’s shape can change with time. For example, those involved may find method short-cuts with time.
legendary journey of the ottawa charter
Posted in Behaviour change theories health promotion

The legendary journey of the Ottawa Charter

Above are the logos of the global health promotion conferences held since its inception in 1986 to the latest in 2016: 30-years. The first logo earned its legendary term – Ottawa Charter – because that conference was held in Ottawa in November 1986.

I first learned about the Ottawa Charter as a third-year medical student two years after it came to light in 1986. After entering into the public health field, I have made “attempts” to implement some elements of it in my practice; first as a medical officer in maternal and child health in a remote district and then as a consultant community physician in mental health and health education (promotion) fields.

This post walks through its legendary 30-year long journey starting from Ottawa in 1986 to Shanghai in 2016.

The birth

The concept of the Ottawa Charter was built on the Declaration on Primary Health Care at Alma-Ata, Russia in 1978. The Charter considers health promotion as a process of enabling people to increase control over and to improve health. The term health refers to a complete physical, mental, and social wellbeing, not merely the absence of disease or infirmity as articulated in 1948.

Writing an editorial to the Health Promotion International on behalf of the “Shanghai stop” held in 2016 – 30 years after the Ottawa Charter – Ilona Kickbusch and Don Nutbeam say “the Ottawa Charter brought a paradigm shift in thinking about how to improve public health”. According to them, from 1986 up to 2016, the Ottawa Charter has made “significant strides forward”. For example, in 2015 the health promotion became a Sustainable Developmental Goal (SDG) – SDG 3 aims to ” Ensure healthy lives and promote well-being for all at all ages”.

Its concept

The best way to describe the concept is to walk through the logo; the logo consists of a red circle and three wings – the action areas.

Ottawa charter logo
The red circle

The red circle – Build healthy public policy – holds each element together; without that everything falls apart. It also symbolizes the need to build policies while working on the three wings.

The three wings

The three wings represent three core action areas: reorient health services, create supportive environments, and strengthen community action together with developing personal skills. One wing – the community action – breaks through the building healthy public policy. The breaking through symbolizes the ever-changing needs of societies and the need of having responsive healthy public policies.

The wing of reorienting health services is worth discussing a little bit more; it symbolizes the need of reorienting health services to prevent illnesses and promote health.

We can also see where health education fits in this circle: Develop personal skills. In other words, health education is a crucial but only one element in health promotion.

The small inner circle

This small circle represents three strategies – enable, mediate, and advocate – that need to use in all five action areas.

Much later, in 1998, the Health Promotion Glossary defined its every word and term. This occurred after the Jakarta Declaration launched in 1997.

Healthy public policy and intersectoral action are the central elements.

However, the eight pre-requisites for health in the Charter is less known;

  • peace
  • shelter
  • food
  • income
  • education
  • a stable eco-system
  • sustainable resources
  • social justice and equity


The Charter has traveled around the globe with many transformations; Following is its journey. Each stop has added some change to the original roadmap. However, we need to accept as Bosse Pattersson wrote in 2011 to the Health Promotion International that the advancements from these stops were heavily underutilized in the world.

The Journey begins,

The first stop: Adelaide recommendations for healthy public policy (1988)

This was the second international conference on health promotion after the Ottawa one. These recommendations explored the healthy public policy theme further and its importance; it creates environments that make the other four action areas doable and sustainable.

It called for all governments to make a political commitment to health by all sectors.

The recommendations made clear about the characteristics of a healthy public policy: it should be explicit, reflect equity in all areas in the policy, and accountable for the health impact of the actors. It further mentions specific subject areas beyond the health sector: agriculture, trade, education, industry, and communications. It means when formulating such policies, health should be considered as an essential element.

At this stop, four priority areas were identified: Supporting the health of women; improving food security, safety, and nutrition; reducing tobacco and alcohol use; and creating supportive environments for health.

For its time, this statement seemed well advanced. South Australia has taken the mantle and moved forward with health for all policies later.

The second stop: Sundsvall statement on supportive environments (1991)

This third conference held in Sweden focused on creating supportive environments. The statement directly addressed policy-makers and decision-makers at all levels. Its call for action was to form broad alliances on the health platform. The statement elaborated what supportive environmental dimensions refer to Social, political, economic, and inclusion of women at all levels.

Furthermore, the statement detailed key strategies to be adopted in creating supportive environments.

  • Advocacy through community groups particularly women’s groups.
  • Education and empowerment
  • Building alliances
  • Mediation to ensure equitable access to supportive environments

In the following year, 1992, the subject of health took a prominent role in the UN’s RIO Declaration on Sustainable Development.

The third stop: Jakarta Declaration, 1997

We can see here the emblem has evolved further from its original one; the outer circle of healthy public policy and the inner small spot in the original logo had merged to form a large blue spot. The three wings originate from the blue spot. And, the wing’s color has become brick-red. According to the designers, this represents the evolution of the original Ottawa Charter to be more open to embracing new players.

The Jakarta stop was the fourth conference as well as the first held in a developing country with the active involvement of the private sector.

This Declaration focused its attention on the determinants of health of the original Ottawa Charter: peace, shelter, food, income, trade, industry, social justice, women empowerment, stable eco-system, sustainable resource use, respect for human rights, and equity. Above all, they recognized poverty as the greatest threat.

Further, it emphasized the clear need to break through traditional barriers within the government sectors, between the government and non-government sectors, and the involvement of the private sector.

The Declaration finally recommended all countries develop appropriate political, legal, economic, educational, social environments supportive of health promotion.

Key messages
  • Applying all five action areas together is the most effective than single-track ones.
  • Choosing settings – schools, markets, mega-cities, the workplace, healthcare facilities – make implementation all five action areas feasible.
  • People should be at the center of decision-making and implementation.

The fourth stop: Mexico ministerial statement, 2000

This statement stated health promotion should be a fundamental component of all public policies and programs in all countries. With the involvement of politicians, the subject of health promotion was brought up to the political arena. Another major development from this stop was the birth of a broad Framework for Countrywide Plans of Action for Health Promotion.

The fifth stop: Bangkok Charter, 2005

In Bangkok, the focus was on the determinants of health. The document acknowledged the UN’s recognition of health as a fundamental right. Moreover, it highlighted major progress that placing health measures at the center in the Millenium Development Goals (MDGs).

The Bangkok statement was named the Bangkok Charter that identified the implementation gap at the regional and country levels and called for member states to follow through. Among the recommended strategies included

  • Building capacity for policy development, leadership, health promotion practice, knowledge transfer and research, and health literacy.
  • Partner and build alliances
  • Invest in sustainable policies

In 2010, The Eastern Mediterranean region, published a capacity mapping tool for health promotion; it was an excellent development after this stop.

The sixth stop: Nairobi, 2009

The Nairobi stop focused on the implementation gap in health promotion; it went further in contrast to the previous ones outlining 59 evidence-based interventions.

A notable follow-up development was the Rio Declaration in 2011. It was a political declaration.

Rio Political Declaration on Social Determinants of Health, 2011

Through this Declaration, political leaders agreed to implement the Social Determinants of Health approach to reduce inequity.

The seventh stop: Helsinki, 2013

This stop again re-iterated the importance of the “Health -in – all – policies” (HiAP) approach. With this, the participants affirmed their commitment to improving equity in health, consider health as a fundamental right without any discrimination. The Declaration called on the governments to,

  • Commit health and health equity as a political priority
  • Ensure effective structures, resources, and processes to enable health in all policies across all levels
  • Strengthen the capacity of the ministry of health to engage other sectors
  • build capacity to provide evidence on social determinants of health, inequity, and effective responses
  • Adopt transparent audit and accountability mechanisms for health and equity impacts
  • Establish conflict of interest measures
  • Include communities

This link provides access to conference presentations;

As a follow-up development in 2017 a global network for health-in-all policies was launched;

The eighth stop: Shanghai Declaration, 2016

This stop was held 30 years after the inaugural Ottawa Charter in 1986. And, one year after the UN Sustainable Developmental Goal (SDG) held in 2015. The Declaration aimed at the 2030 agenda of the Sustainable Developmental Goal (SDG). It focused on four themes;

The Declaration called to action,

  • To recognize health as a political choice
  • To counteract interests detrimental to health and remove barriers to empowerment – especially for girls and women
  • To accelerate the implementation of the SDGs through political commitment and financial investment in health promotion

In parallel to the Declaration, the city mayors who attended the conference gave birth to another revolutionary document: Consensus on healthy cities.

The journey continues…

social norms
Posted in Behavioral theories message framing

How social norms shape our behavior – I

You must have been into a library; you stay silent. That is a classic social norm example. Another common one is littering. As we all know social norms can either be socially desirable or socially undesirable.

Every day we adhere to social norms that are an array of unwritten sets of rules we follow. In a way, these play a crucial role in the smooth functioning of a society. Once we deviate from it, we can expect negative consequences.

Robert Cialdini deconstructs the concept further; he describes two types of social norms: Descriptive and injunctive.

Descriptive (popular) social norms = What is being done

The descriptive social norm refers to actions that others seem to be doing. Irrespective of its impact – either socially desirable or socially undesirable – social norms exhibit a “contagious effect”. Take the example of littering; seeing others maintaining a clean environment persuades us to keep those places clean; in contrast, if we see others litter a place, we tend to follow it.

Need evidence?

Robert Cialdini’s 1991 report provides evidence. He together with his team demonstrated how “littering begets more littering”. Not only that, they further showed when a norm began to change; in a perfectly clean environment, the subjects adhered to that social norm even with one litter; with the increase of the number of litters, the “slippery slope began”. We tend to change our perceived descriptive social norm from the ” no one litters here” to “everyone litters here”.

This certainly goes beyond littering, even to policy making!

The interesting thing here is that we, most of the time inadvertently, promote socially undesirable norms with our statements highlighting socially undesirable behaviours as the norm. It results in a dangerous “boomerang effect”.

David Halpern in his excellent book memoir – “Inside the Nudge Unit” (David Cameron’s unit where he worked) writes, ” I have lost count of the number of examples of Robert Cialdini’s “big mistake” that I have seen”.

Injunctive social norms = what ought to be done

in contrast to the descriptive social norms, injunctive social norms refer to actions that people either approve or disapprove of (as we perceive). It could either be a displaying “do not litter” notice, the presence of a designated place to dispose of garbage, or what we see that another person removes and properly disposes of the litter.

As I understand, there is a very important difference between the descriptive social norms and the injunctive social norms; the former can be situation-specific while the latter’s influence can be very robust. For example, Cialdini and his team’s research demonstrated seeing that someone picking up and removing litter from a clean environment (social disapproval) lead others to imitate that behavior not only at that particular place but in other settings also.

How can we apply the above concepts usefully?


  • Using descriptive social norms is like a double-edged sword; it becomes effective only when most people engage in socially desirable behaviors; if most engage in socially undesirable behaviors it will backfire.
  • If we suspect most people engage in socially undesirable behaviors, Cialdini suggests using injunctive social norm focus.

I will write in a later post how descriptive and injunctive social norms influence, for better or worse, during this COVID 19 pandemic.

Posted in #covid-19 message framing

Do your part – stay apart; more relevant now

This message becomes more relevant now than before with the growing presence of the COVID 19 variants. The new variants are more transmissible; for example, the UK variant is said to be 56 percent more transmissible than the original COVID 19 virus.

What does that mean?

It means if the original one takes 20 days to double the number of us infected, this variant will do it within 10 days. Some epidemiologists predict the numbers can go up by more than 10 fold if the current lockdown restrictions are removed.

Posted in #covid-19 message framing

Message framing effect on vaccine hesitancy-II

In 2018 I explored the message framing effect on measles vaccine hesitancy among the US population. In that post, I highlighted the Hendrix et al. (2014) finding that more parents were modestly persuaded to vaccinate their children when the benefits to the child were emphasized when compared to the standard CDC information. That is about the measles vaccine. And, they explored parents’ intentions to vaccinate their children.

We do not know whether the same holds true for people living in other cultures and other vaccines.

This post is about a study on the influenza vaccine and 222 patients who attended a tertiary hospital in Turkey. These researchers have explored this personal-benefit versus social-benefit dualism with regard to the perceived risk level of the people. In their field experiment, they found the intentions to get vaccinated were higher among those perceived as high-risk when the personal-benefit was emphasized. On other hand, the intentions were higher among those who perceived low-risk when social-benefits were emphasized. In other words, at least for this population further division of the target audience and customizing the message accordingly is more beneficial.

Posted in Uncategorized

Face mask comparison

Germany mandated the wearing of surgical masks, commonly called N95 while traveling public transport and public places two days ago. Previously clinical studies have shown cloth masks’ efficacy varies from 30 percent to 80 percent. Last December, a German community-based comparative study found normal masks’ efficacy as 45 percent.

The following image was taken from the CNN World website; it clearly compares the efficacy of cloth masks, surgical masks, and the N95 (respirator).

Mask comparison (source: CNN World)
Posted in #covid-19 Risk communication

Is Covid 19 different from the influenza flu?

Even after a year, some are grappling with the same old question: Is Covid 19 different from the seasonal flu?

How do we communicate the risk convincingly to this target audience? Obviously, we need to compare number of deaths due to Covid 19 with the number of deaths due to the seasonal flu. The Centre for Risk and Evidence Communication in the University of Cambridge has done exactly that.

Look at the following graph;

It compares the number of COVID 19 deaths with the deaths from influenza flu and several other common causes. As we can clearly see that the number of Covid deaths sharply increases with age when compared to the deaths from influenza flu. It convincingly debunks the claim that Covid 19 is not different from influenza.

Source: Winton Centre for Risk and Evidence Communication, University of Cambridge

US CDC COVID-19 message
Posted in COVID19publichealthresearch Paradoxes

US COVID-19 pandemic: Cases vs deaths paradox

The US CDC data reveals an interesting age-specific case versus deaths paradox.

Look at the following graph. I created the graph using data available at the US CDC website.

US COVID-19 cases versus deaths paradox
(Data source: US CDC)
  • Of all the COVID-19 cases, 85.6 percent occurred among those aged equal and below 64 years.
  • In contrast, of all the COVID-19 deaths, 80.6 percent occurred among those aged 65 and above.

Now, my message is clear and straightforward based on this graph: Minimize the contact between these two age groups.

How can we minimize the contacts between these two age groups?

My suggestions are;

  • Provide financial and other incentives to those aged 65 and above to stay at home.
  • Mobilize all regional and local community organizations and all faith groups to create supportive environments to separate the two groups.
Posted in #covid-19 Risk communication

A face mask is not a substitute for physical distancing

A face mask over your mouth AND nose is not a substitute for physical distancing;

stay at least 6 feet apart from those who don’t live with you.

#WearAMask over youth mouth AND nose in addition to staying at least 6 feet apart from people who don’t live with you and washing your hands often.