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Infectious Diseases

Updated 23 March 2020

How mild, undocumented infections could lead to an even bigger coronavirus spread

A new study indicates that one of the biggest culprits enabling the coronavirus to spread even faster could be mild, undocumented cases, emphasising the need for social distancing.

As the official number of new coronavirus cases in South Africa increases, we can't help but wonder how many more unsuspected cases there might be.

On Sunday, 15 March 2020, the president suggested social distancing, but many South Africans don't understand exactly how such drastic steps could help curb a serious outbreak.

New research now suggests that those mild, undocumented cases might be the ones that could rapidly accelerate the outbreak.

What the research entailed

The study was published in JAMA Science. Researchers wanted to emphasise the importance of documenting even the mildest, asymptomatic cases as people who carry the Covid-19 virus without any knowledge thereof can cause a large number of infections as they spread the virus.

The authors wrote: “The fraction of undocumented but infectious cases is a critical epidemiological characteristic that modulates the pandemic potential of this virus. These undocumented infections often involve mild, limited or no symptoms and hence go unrecognised, and, depending on their contagiousness and numbers, can expose a far greater portion of the population to the virus than would otherwise occur.”

To determine these undocumented cases, the researchers designed a model-inference framework to estimate exactly how contagious any undocumented infections were in China during the weeks before and after the shutdown of travel in and out of Wuhan, the first location of the outbreak.

Their findings indicated that a large number of Covid-19 cases were undocumented before severe travel restrictions were implemented, and that affected the spread.

As soon as travel bans and measures of social distancing were put into effect, the spread tapered off.

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The importance of social distancing

Right now, there are certain criteria that will determine whether someone in South Africa should be tested for the Covid-19 virus.

We also know by now that the disease, Covid-19, has a median incubation period of 5.1 days, where someone who is infected doesn’t show any symptoms. Such a person may be blissfully unaware, or just suffer mild symptoms, and still spread the disease through droplets.

According to experts, social distancing is an important factor in helping to curb new outbreaks, especially when people are not aware that they might be spreading the virus.

As several sporting and culture events are being postponed around South Africa, it’s essential for us to see how this may help curb an already growing pandemic.

During the influenza pandemic of 1918, medical technology wasn’t as advanced as today, no facilities for testing were readily available and air travel not as prevalent. But several sources show that the closure of schools, shops and other public gatherings (also known as non-pharmaceutical interventions) worked. Cities which implemented these restrictions had lower mortality rates. And while experts are still racing to develop a vaccine, the best thing to do is to curb the spread.

How would I know if I’m infected?

Right now, the World Health Organization (WHO) calls for stringent testing measures. Unfortunately, this is easier said than done – not only is testing expensive, but it is also logistically impossible to test everyone.

Therefore, the responsibility falls on everyone to act as if they could all potentially spread the virus, even if they don’t show symptoms or are potentially not at risk of severe symptoms.

Do the right thing

Right now, we are advised to take the following precautions:

  • Limit your social interactions.
  • Find out if your office allows working from home.
  • Keep your distance from others if you have been in a high-risk area.
  • Practise stringent hygiene, like washing your hands, especially if you work with the public.

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READ | Coronavirus: What are the criteria for a suspected case?

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