The director general of health, Dr Ashley Bloomfield speaks to media during a press conference at the Beehive (Photo: Hagen Hopkins/Getty Images)

A beginner’s guide to public health

The Covid-19 crisis has propelled the field of public health to the foreground. A few simple public health concepts could help keep us on track as we near one month in level four, writes Louise Thornley.

Public health is suddenly part of everyday conversation. Many of us have become addicted to the daily Covid-19 update, observing from our living rooms as the pandemic leaders and journalists discuss concepts like case definition, contact tracing and asymptomatic transmission.

The collective health of New Zealanders is taking priority over everything else. And in the name of public health, we’re all required to change our lives dramatically.

For those of us who work in the field, it’s always been a red-hot topic. The classic definition comes from 1988, when the epidemiologist Sir Donald Acheson defined public health as “the art and science of preventing disease, prolonging life and promoting health through the organised efforts of society”. 

What could be hotter than stopping illness before it strikes, and helping create healthier policies and places where all people can live fuller, healthier lives?

But before 2020, public health wasn’t such a headline-grabber. It’s just not as sexy as a surgeon saving a child in hospital, or a primary care practitioner assessing a patient in just 10 minutes, prescribing exactly the right drug to help an immediate need. 

Public health is about prevention – harder to capture with a snappy headline or a short soundbite. It involves long reports and detailed graphs. It’s about in-depth analysis of data and trends, horribly slow policy processes, tireless advocacy by committed people, and finally, brave decisions by politicians. 

Public health is things like government efforts to reduce smoking and improve the condition of housing. Tackling institutional racism, ensuring food safety and clean drinking water, and encouraging healthy urban design to make it easy for people to walk or bike more often.

Public health is things like government efforts to reduce smoking and improve the condition of housing (Photo: Hannah Peters/Getty Images)

What we mean by public health is sometimes confusing to others. When I’m asked what my job is, the response “public health researcher” is often met with a blank stare. My own partner admits that at first he didn’t have the foggiest idea what I did for work.

And yes, public health has several meanings – all of which you may have heard in the media recently. It can mean publicly funded health services, in contrast to private health services. Or it can refer to the public health system as a whole: doctors, nurses, hospitals, primary care, physiotherapists, pharmacists, and district health boards.

What public health usually means in this Covid-19 pandemic is what Acheson said above – except he forgot the crucial task of eliminating inequity and disparities in health outcomes. In Aotearoa, public health strives to improve health equity and outcomes in Māori health, and in the health of others like Pacific communities and people on low incomes.  

On the surface, public health can appear to involve a lot of “don’ts”: don’t smoke, don’t eat those things, don’t drink and drive.

Healthy actions by individuals do matter. But we don’t all have the same opportunities to make healthy choices. Societal pressures make some healthy choices less feasible or even impossible. 

Things like structural inequalities, systemic discrimination, financial constraints and limited access to health resources can all limit the power that an individual has over their own health decisions. That’s why public health focuses on the social, cultural, economic and environmental factors that affect people’s wellbeing.

So public health is a health specialty that works to prevent disease and promote health and equity through society’s organised efforts. In the case of this pandemic, we’re all getting organised. We’re part of a large collective effort to prevent and reduce the impact of Covid-19, ably led by prime minister Jacinda Ardern and the director general of health, Dr Ashley Bloomfield.

Not to name drop, but when I first started in public health nearly 20 years ago, Ashley Bloomfield was my manager. Now he’s a media sensation, the subject of adoring tributes.

Bloomfield introduced me to the baffling-but-fascinating world of epidemiology and biostatistics, sending me off to medical school to study a post-graduate qualification in public health. There I learned about what epidemiologists do, what a population-health approach is, and ways to analyse and quantify risk and exposure to risk. 

These concepts can help explain why it’s so important that we all keep staying at home this weekend, as we near the end of four weeks in level four. This is to reduce every possible chance of Covid-19 transmission and to each play our part in this collective journey we’ve been thrust into.

If you find you’re wavering, asking yourself why are we doing this again, please call to mind these three public health concepts:

It’s about us, not just me or you (the population-health approach)

Covid-19 requires us to think about health in a different way. It’s not just about our own health as individuals or families, though that is also important. The population-health approach aims to improve and maintain health across a defined population. Its focus is the health outcomes of a group of individuals, and how these outcomes are distributed across the group. 

In the Covid-19 crisis, we’re interested in the health outcomes of New Zealanders as a whole: Māori and Pacific communities, older people, the immune-compromised and people in the identified clusters of Covid-19 cases, among others. And we’re interested in the social and economic outcomes for people most affected by the Covid-19 response – economic factors have major effects on health.

We’re in this together: our own health and wellbeing (individual-level) is deeply connected to the health and wellbeing of each other (population-level).

We are all at risk of getting this virus

Anyone can get this virus. Teenagers have died of Covid-19. Some groups have a higher chance of being worse affected, but we are all “at risk”. Human health risk assessment is an approach used to understand the nature and size of health risks in people, groups and communities. 

When assessing health risk, a health hazard is something with the potential to cause harm to the health of individuals, groups or the wider community – that’s the virus that causes Covid-19 disease.

A health risk is the probability – or likelihood – that being exposed to a health hazard such as the virus will cause harm (getting sick with Covid-19 infection). 

We all have ways to reduce how exposed we are to risk

The good news is that in our daily decisions we can reduce how exposed we are to the health risk of Covid-19. We’re not just following the rules of this rāhui/lockdown because we’re obedient and admire our leaders (though this may also be the case). We’re changing how we live for now so that we can all reduce our exposure to Covid-19. 

Epidemiologists define exposure as the degree of contact with a hazardous disease agent (the virus), where transmission could have occurred. When my friend returned from Australia a few weeks ago, she had higher exposure to Covid-19 than she would have without that trip.

Where I live, our local dairy owners are doing everything they can to comply with the level four safety rules for the benefit of our community. Essential workers can take steps to reduce their risk, but are still exposed to more risk than those of us who aren’t in essential work right now. 

This weekend, you can reduce your exposure to Covid-19 by staying home and only interacting with people outside of your bubble by phone, text, email or video.

It’s not about blindly following the rules. It’s about acting in ways that reduce every possible chance this virus has to infect us. As the prime minister put it: “be a good human”.

Our wellbeing is intertwined. When you stay at home and limit physical contact to your household, you break the chain of transmission. Your choices help to keep my family members well, free our hospital beds for those who need them, and to help all of us to stamp out Covid-19.



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