Wuhan Coronavirus: The Real Threat Level

I use the label ‘Wuhan Coronavirus’, but it is also described as ‘novel coronavirus’, and other names including perhaps confusingly just ‘coronavirus’. This is a disease that has managed to raise alert levels before even getting a unique name.

What is a Coronavirus?

Answer: A family of viruses, ranging from the common cold to SARS, influenza, and others. They range from ‘relatively harmless’ to deadly. More information is available with a quick search, but generally at the moment use of the term ‘coronavirus’ is refereeing to the new version that does not yet have an official name. even though technically you could describe anyone with a cold as having coronavirus.

First, The Good News

So far over 4,700 cases of Wuhan Coronavirus are being treated with approximately 100 fatalities. This would indicate a mortality rate of around 4%, but as the denominator is those being treated, and there is an unknown number not requiring treatment, the actual rate should be lower. SARS had a mortality rate of approximately 10%, with around 8,000 cases and approximately 750 deaths. MERS infected around 2,500 people and resulting in around 850 deaths. Influenza has a mortality rate of around 1%, so this new coronavirus is closer to a new ‘flu’ than SARS or MERS in terms of mortality rate…at least so far.

Getting Infected?

As with the common cold, the normal path for transmitting infection is a carrier coughs or sneezes, creating tiny airborne droplets that can be inhaled by others, land on the skin of others, or on the skin of the carrier and then be physically transmitted to others.

Because coughing and/or sneezing are symptoms and normally required for the disease to be transmitted, we normally describe people displaying symptoms as ‘infected’. However, with all coronaviruses, there may be a significant number of people who ‘catch’ the virus, but with whom things do not progress to the display of symptoms. Such people may have immune systems extremely effective in dealing with the virus, or the initial exposure may be at a low level. It is normally impossible to know how many people display no symptoms, as there is only screening of people with symptoms.

In all, ‘infected’ usually means ‘displaying symptoms’, but may not include all people who have/had the virus in their system.

Now, The Bad News

Reports are that Wuhan coronavirus can be spread even by those not yet displaying symptoms. Perhaps even by people who would never display symptoms. This suggests just breathing is sufficient create vapour containing the virus, or there is yet another mechanism. Simply put, we may be seeing new ground in terms of how this virus can spread.

While the mortality rate is lower than SARS or MERS, this can easily be offset if more people become infected. If a virus with a mortality rate as low as even 1% was to infect 1/8th of the worlds population then there would be even 10 million deaths. The Spanish flu, another coronavirus, created an even greater level of devastation.

Rate of Infection.

Over 4,000 people being treated just 2 months after ‘case 1’ is rather worrying. With a believed 2 week incubation period, that would be only 5 cycles of incubation. Even if the two weeks is longest time, and one week is more representative, then there are 9 cycles. From 1 to 4000 in 9 one week cycles, is an increase of just over 2.5 times more cases every week, or 53 times more cases every month. At that rate, we would reach 100,000 cases before March, and over 1 million before the end of March, and the entire population as soon as May, so obviously things cannot continue at that rate.

The 2.5 times per week could only continue in an infinite population. What limits that growth in a finite world is that many infections become multiple infections of the same person, or infections of those already infected. Contained within a given area, there simply becomes less and less new people to infect.

This gives and extra factor, ‘rate of contact with uninfected people’ factor. So far, this factor can be considered to be 1.0 or 100%, and perhaps even higher in artificially constrained environments such as cruise ships, but the rate will eventually drop to towards zero (0.0) and the first wave of the disease reaches infecting everyone it can.

Conclusion: Potentially a Wild Ride

The ability of medical science to understand how to handle epidemics and even create vaccines is way beyond what it was at the time of the Spanish Flu, so repeating the estimated 50 to 100 million killed at that time sounds unlikely.

However, in 1918, plane travel was not a reality so any disease spreading internationally had to happen far more slowly back then.

The growth rate of infection above does put into perspective the fact that while just over 4,000 cases worldwide now, the next month is critical. Does it reach close to the 180,000 possible by the end of February, or are there cases now in areas where further spread is not possible?

It will take another month to know the answer, but if the quarantine period really is two weeks, half of the next months infections may already be in place.

Stay tuned for what is potentially going to be one wild and frightening ride.

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