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What 'flattening the curve' means and how you can make a difference

Chief Medical Officer Dr Tony Holohan said the next seven days are “vital” with Covid-19.

A graph showing the difference flattening the epidemic peak makes in the number of cases over time.
A graph showing the difference flattening the epidemic peak makes in the number of cases over time.
Image: Department of Health

THERE HAS BEEN a lot of talk about “flattening the curve” of Covid-19, but what does this actually mean?

As cases of the coronavirus increase day by day in Ireland and across the world, the number of  cases has differed from country to country.

Countries like Italy saw a large spike in cases over a short period of time, whereas others, like South Korea, have had a much steadier increase over the past few months. 

In an effort to spread out the number of diagnosed cases here, the Irish government has said it is trying to ‘flatten the curve’ of the epidemic. 

What does this mean?

Flattening the curve of Covid-19 cases is about slowing the spread of transmission over a longer period of time through measures like social distancing, and closures of schools and workplaces.

If we picture this increase on a graph, the ‘curve’ refers to how the increase in transmissions can be visualised. Flattening the curve is about making this look less extreme.

It also means that there is less pressure on the health service as there isn’t as large a number of people being diagnosed at the same time.

Instead, things are spread out and the health service has more time to deal with and plan for cases.

This image from the US’s CDC shows how we can visualise ‘flattening the curve’:

PastedImage-83523 Source: CDC

“In a pandemic like this where the virus is pretty good at transmitting from person to person, we can have an exponential increase in the number of infected people and that can lead to a peak of epidemic that completely swamps the health service,” explained Dr Kim Roberts, leader of the virology research group in Trinity College Dublin. 

Roberts said measures like social distancing are aimed to slow down this transmission. 

“So we slow down how the virus spreads through the population and we reduce the size of that peak so that although overall the same number of people might become infected, it will be over a longer period of time and the health service won’t be overwhelmed.” 

How is Ireland trying to flatten the curve? 

Countries around the world have taken different approaches to tackling the spread of Covid-19. 

In Ireland, schools, colleges and childcare facilities have been closed since last Friday. Pubs closed yesterday and workers who can continue their jobs from home have been advised to do so. 

The government has informed people about social distancing and avoiding large groups in an effort to reduce a large surge in transmissions. 

To limit the spread of the infection, Kim Roberts explained that reducing social interactions can have a huge influence on numbers. 

“If we assume everyone who has Covid-19 will pass the virus on to an average of 2.5 people, and that transmission occurs on average five days after exposure, then within a month a single infected person can contribute to the infection of 244 people,” she said. 

“If the transmission rate is reduced to 50% and each infected person instead passes the virus on to an average of 1.25 people then in a month, that infected person only contributes to the infection of four people.”

How can people help to reduce the transmission of Covid-19?

Chief Medical Officer Dr Tony Holohan gave a list of advice for people to follow yesterday.

His advice is:

  • Reduce your social contacts – see only a handful of people in your network
  • Distance yourself two metres from people in shops and supermarkets
  • Stop shaking hands or hugging when greeting people
  • Avoid touching your eyes, nose or mouth
  • Wash your hands regularly and practice cough and sneeze hygiene
  • Clean and disinfect frequently touched objects and surfaces
  • Check on your vulnerable family members and neighbours
  • Work from home where possible

Kim Roberts said people need to “be reasonable about risk and assessing the transmission risk”.

“Going to a supermarket to pick up essential supplies, if you wash your hands as soon as you get home and the shop isn’t full of people, that has a low transmission risk,” she explained. 

However, going to a crowded bar and being close to a lot of people has a higher transmission risk. 

“Similarly, meeting a friend in a park is going to be less of a transmission risk than going to somebody’s house or meeting in a cafe.

“It’s about thinking about what the risks are and trying to live as normally as possible, but change behaviours so that we minimise transmission risk.”

“We all need to realise that staying home saves lives… We also need to realise that we’re not trying to stop all transmission, we’re trying to slow it down.”  

Dr Anthony Staines, a professor of health systems in Dublin City University, said people during this time should mind their neighbours and offer social supports, while maintaining social distancing. 

“Contact tracing, testing and social isolation is what controls this pandemic and nothing else will control it,” he said. 

Have these measures worked anywhere else in the past?

Yes. Countries such as China and South Korea have slowed down the spread of Covid-19 during this pandemic already.

In China for the past two months, thousands of new cases were diagnosed each day. There were 36 new cases confirmed in the country yesterday. 

Past examples can be seen during the 1918 flu pandemic which killed around 50 million people worldwide.

In Philadelphia in the US, no social distancing measures were put in place and a parade with crowds of 200,000 people took place during the height of the pandemic. This led to a growth in thousands of infections very quickly.

In St Louis, however, parades were cancelled when the pandemic was at its peak.

A month after the parade, more than 10,000 people died from the flu in Philadelphia, according to the Centers for Disease Prevention and Control (CDC). In St Louis, the death toll did not rise above 700. 

The CDC in the US cited this as a “deadly example” to show the benefits of cancelling mass gatherings and introducing social distancing during pandemics. 

During the Severe acute respiratory syndrome (SARS) epidemic, Anthony Staines said “stringent quarantine measures were put in place and that worked in China and Canada”.

China was the worst affected country by this coronavirus, with over 5,000 confirmed cases.

In Canada, over 250 cases were confirmed, by far the highest number of any country outside Asia.

When will we know if social distancing measures are working to flatten the curve? 

Tony Holohan said yesterday that the next seven days will be “vital” in the spread of the disease. 

Anthony Staines said it will take “at least a week to 10 days” to see if the measures are working.

“What we see today is infections from between five and 10 days ago,” he explained. 

What will happen even if we do nothing, at some point it will go up and then it will reduce no matter what we do.

However, by flattening the epidemic curve the numbers will be spread out over a longer period and the health service will be less overwhelmed. 

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