'Flattening the Curve’ Explained

By Kalani Kumarasinghe

Flatten the curve! It’s a hashtag that accompanies every other post you see on social media. Many have been talking about this curve that needs flattening. But what is it all about and why does it need to be flat?

The curve, what is it?

Responses to infectious disease epidemics make use of a growing body of data to make informed decisions. One of them is the epidemiological curve or epicurve. It is one of the most trusted tools used by epidemiologists and other decision makers for evaluating the forces at work when it comes to infectious diseases.  

Epidemic curves describe the number of new cases over time, also called incidence. Incidence remains one of the most important sources of information for health authorities, especially early on in an outbreak of a disease.  The data specifically illustrate the number of new cases per time unit, based on the date or time of the onset of symptoms. In other words, epicurves give us a simple, visual outline of epidemic dynamics, which can be used for assessing the growth or decline of an outbreak.

Why does it need to be flat?

When fighting an epidemic or a pandemic, the goal is to completely contain and stop the spread of the disease. But even just slowing the spread of the disease is crucial to managing the situation at hand. In Wuhan, China, the epicentre of Covid-19, the disease spread fast and caught the region unaware. By just February hospitals were at capacity. Ambulances were hard to come by and hospitals eventually turned patients away, as the facilities were completely overwhelmed.  It was clear that healthcare providers hadn't quite gotten the handle on what they were grappling with. Social distancing measures therefore, weren't practiced until it was too late. This resulted in a steep spike in the epidemic curve.

By slowing the spread of the disease, the number of cases that are active at any given time is reduced. What this does is give some time for the hospitals including medical personnel and the authorities such as the police to prepare and respond, without being overwhelmed. To keep our doctors, nurses, hospitals and police officers from being overtaxed with the number of active Covid-19 patients at a time, the ultimate goal of our health authorities would be to flatten this curve. 

An epidemic curve with and without social distancing (Source: CDC)

The curve can take various shapes depending on how, when and how fast the disease spreads. The above graph illustrates two curves. Over time, both these curves would add up the number of new cases. When more people are diagnosed with the virus in a given day, the higher the curve would be, which means that the disease is spreading rapidly. A low curve or a flattened curve will indicate that the virus is spreading slower, meaning that a lesser number of people are diagnosed with the disease on a given day. The dotted line meanwhile illustrates finite resources available to treat the sick or the amount of cases the healthcare system is able to handle. Therefore, flattening this curve, or slowing down the number of new cases, prevents overwhelming and overloading our entire healthcare system. The best practice to make sure that the curve remains flat is social distancing. 

How to flatten the curve

By just last evening (Tuesday, March 31) Sri Lanka recorded 21 new patients who tested positive for the coronavirus, the highest number of patients diagnosed within a day since the outbreak of the disease early March. Deputy Director of Health Services at the Ministry of Health Dr. Paba Palihawadana speaking to the Daily Mirror said that minimizing community transfers of coronavirus remains a high priority for Sri Lankan health authorities. "We are trying to maintain the caseload at this level. This is why we are identifying and tracing close contacts of all the patients who have tested positive. With the quarantine centres and self-quarantine measures in place, we have tried to minimize community transfers,” she said. 

There is no vaccine or a specific anti-viral treatment for Covid-19.  Many experts credit the rigidity of social distancing measures practiced in Wuhan to the drastic reduction in new cases being reported. This is also why similar practices, with state enforced lockdowns and curfews are placed in many countries including Sri Lanka.

How can you help?

‘’If we are be able to minimize the community transmissions itself, then there would be no spread from one person to another. It means that we would be able to flatten the curve,” Dr. Palihawadana said.  She added thus far in their investigations, community clusters have been at a minimal. “At the moment, there is no further spread beyond the family, this is what we have observed. We have observed very close family clusters, but not beyond that,” she noted. 

However, maintaining the dynamics of this deadly disease at this level has not been easy. In fact, convincing several errant cases to seek assistance of the authorities has been a challenge, which in turn has endangered the wellbeing of many others across the country. “People should understand their responsibility and report themselves. They should inform the health authorities and they should come to the hospital for identification. The general public meanwhile if they do not have symptoms, should maintain social distancing, hand-washing and hygiene etiquette and also avoid gatherings,” she said that these practices are expected from the community level in order to contain the spread of Covid-19. 

“If someone has the symptoms, they should promptly inform the health authorities and they should not hide their illness. Suppose someone is sick, that person should tell the doctor the correct history of the illness. They shouldn't hide their actual symptoms which is happening,” she added highlighting that it was the collective responsibility of all Sri Lankan citizens at this critical time.