Does everybody show COVID-19 symptoms?

As an employer amidst the COVID-19 pandemic, your role will have seen a dramatic shift over these last few months

Safety in the workplace – whatever form that takes – is now your primary task.

Before Coronavirus, health and safety could largely be covered by a decent risk assessment process being followed, a few briefings here and there to ensure staff and H&S officers all know their roles towards safety, and besides the exercising of a little common sense – you could ‘kind of’ forget about it and let them all carry on in a well-informed capacity.

You’ve crossed your t’s and dotted your i’s. You’re all good to go.

Safety has changed drastically as soon as COVID-19 arrived. Virtually
overnight, employers have become firefighters. Except the fire is invisible,
you have no idea what is flammable around you and if you’re not
careful, you won’t have any protection to put it out either.

That may sound dramatic, but if we remember that your role as an employer is to keep your workers safe, neglecting the importance of protection when you have a silent killer in the midst isn’t going to bode well.

If your premises are currently open for business – prevention of COVID-19 transmission is your number one priority. And you can’t do that job, if you don’t know what you’re looking for. Knowing your killer is in stealth mode, gives protection a whole new persona.

What Is The Official Percentage Of Asymptomatic Coronavirus Cases?

The truth? We don’t know. Nobody does.

But would it make any difference to your operations, if you knew that there could be anything between 5% to a whopping 80% of workers with COVID-19 having NO symptoms?

We’ve tried to research some clear numbers on the asymptomatic people testing positively, but that relies upon all reports, providing clear data using exactly the same criteria.

It also relies on data being accurate on how and who were tested. Let’s scrap that plan then if we’re to keep our own integrity here!

However we did find examples of situations where there was an outbreak, multiple people were tested quickly and efficiently, and results of the entire population affected at the time were recorded.

If ‘seeing is believing’ is your current course of action, it’s not going to work. The results are pretty shocking, and we don’t say that lightly with most test populations having a majority of tested cases being asymptomatic…

The following results were taken from The Centre for Evidence-Based Medicine website. They trawled online by searching LitCovid (a subset of Pubmed), medRxiv, Trip, Scholar and Google and retrieved 21 reports for analysis.

We didn’t want to distort any of their findings so we’ve provided their full Table of Studies Assessing Asymptomatic Cases below so you can see for yourself…

Setting Proportion Comment
Diamond Princess cruise ship, Yokohama, Japan (n=-634 tested positive). [1] 18%

(95% credible interval 16%-20%).

Most infections occurred before the quarantine started.
Vo’Euganeo, 50 km west of Venice, Italian village [2] 50% to 75%—were asymptomatic In an open letter to the authorities in the Tuscany region
MERS-CoV [3] Increased from 0% to 29% over time As the MERS-CoV progressed over time there was more identification of asymptomatic individuals due to increased surveillance and contacts testing.
328 adults in Shanghai [4] 13 (4%) patients were asymptomatic
Japanese nationals evacuated from Wuhan (n=565) [5] 31% (95% CI: 7.7% to 54%) Based on temperature screening before disembarkation, interviews on symptoms including fever, cough, and non-specific symptoms
23 Residents of a Long-Term Care Nursing Facility King County, Washington[6] 10 (43%) had symptoms, and 13 (57%) were asymptomatic.

Seven days after testing, 10 of 13 asymptomatics developed symptoms

Symptom-based screening could fail to identify approximately half of nursing home residents with COVID-19.
Airport screening of travellers [7] 17% undetectable by typical screening procedures Based on: A familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: Lancet. 2020;0(0):S0140-6736(20)30154-9.
Hospitalised in Beijing, China (n=262)[8] 13 (5.0%) asymptomatic cases
391 cases including 148 family index cases in Zhejiang Province [9] 54 (14%) asymptomatic higher family secondary attack rate, the secondary attack rate of spouses is higher than other family members.
Chinese perspective [10] Over the past few days, asymptomatic patients were found in many Chinese cities. Whether asymptomatic people can transmit SARS‐CoV‐2 to others is unclear.

Another uncertainty is whether those who are asymptomatic can cause large‐scale infections.

36 children, Zhejiang, China [11] Asymptomatics, 10 (28%) 7 had acute upper respiratory symptoms (19%)
Data-based analysis, modelling and forecasting of the COVID-19 outbreak [12] The number of asymptomatic and mild cases with subclinical manifestations that probably did not present to hospitals for treatment may be substantial; these cases, which possibly represent the bulk of the COVID-19 infections, remain unrecognized,
166 new infections in China [13] four-fifths of cases are asymptomatic, China figures indicate  Numbers quoted not verifiable
Nanjing, China (n=24) [14] 5 (21%) developed symptoms (fever, cough, fatigue etc.) during hospitalization.
450 case reports from 93 Chinese cities. [15] estimate that people who had not yet developed symptoms transmitted around 10% of the cases they studied.
 People’s Hospital of Daofu county. Tibetan population (n=83) [16] Asymptomatic carriers 22% The median age of asymptomatic carriers was 31 years and 1/3rd were students, aged <20 years.
WHO Q&A: Similarities and differences – COVID-19 and influenza [17] suggest that 80% of infections are mild or asymptomatic,
Iceland [18] 50% of the people who tested positive had no symptoms.” See also: First results of the voluntary screening in Iceland[19]
CDC [20] A significant number of individuals that are infected actually remain asymptomatic. That may be as many as 25%.
Interim Clinical Guidance for Management of Patients with Confirmed Coronavirus Disease [21] Among children in China, illness severity was lower with 94% having asymptomatic, mild or moderate disease,
Northern Italy, 60 volunteer blood donors [22] 40 (67%) tested positive

 

They also go on to say…

“We also learnt that there is not a single reliable study to determine
the number of asymptotics. It is likely we will only learn the true
extent once population based antibody testing is undertaken.”

A minority of cases from the above populations evolved to show they were pre-symptomatic rather than asymptomatic, but either way, at the time they were tested, they looked and behaved like otherwise healthy individuals.

There are also cases where symptoms are present, but they are not what most people would expect. This article from Sky News shares how Anosmia – a loss of taste and smell – has now been added to the official list of Covid symptoms. This new information is thought to be capable of adding an extra 2% to the known cases.

There are also multiple symptoms that show up in usual day to day life such as diarrhoea, abdominal pain, fatigue, skin symptoms such as rashes, lesions or chillblains. The list is very long and doctors globally are encouraging people not to self diagnose.

What Type Of COVID-19 Testing Do I Need For My Employees?

In light of all of that information, it is nigh on impossible to rely on Coronavirus guesswork.

It is now widely accepted that antibody testing is key to the global exit strategy from the disease. Legislation is being revised in some industries to make testing compulsory – for example testing ALL seafaring crew, pre and post boarding ships.

There are currently two principal types of commercially viable test for occupational screening of employees – antigen (PCR) testing and antibody testing. You can read more about these in our previous article ‘Why It’s Critical For Companies To Screen Employees For Covid-19’

Both tests help employers equip themselves with information to help them decide which measures to put in place to contain the outbreak – and consequently inform them on how they can safely return a workforce back to work.

Once tested, where Covid-19 is concerned, employees can then be placed into the following categories, to give you a clearer plan of action when returning people into the workplace:

  1. Totally free from any infection and never previously infected
  2. Totally free from any infection and recovered from previous infection
  3. Infected, without symptoms and within the widely accepted median 5-day incubation period
  4. Infected, past the incubation period and with symptoms
  5. Infected, past the incubation period & without symptoms
  6. With symptoms but not infected with Covid-19 (e.g common cold)
  7. Relapsed/reactivated cases – scientists are studying this concept as ‘relapsed’ patients increase

Returning To Work Safely

If you are concerned about returning your employees to a safe working environment – particularly if workers are operating within close proximity to each other – the safest way to do this is to get a clear picture of their overall health through testing.

Here are some articles we put together previously on creating a safer working environment:

If you need more information on how to buy COVID tests for your employees or equip them with PPE kit, our team is here and ready to fast track your protection to you.


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