Wuhan pneumonia in context – why we need not overreact 20200131

There seems a universal (well at least in HK) panic about the Wuhan pneumonia outbreak, with at least 95% of the people we see in the streets wearing masks – a spectacle – and many organisations completely shutting down (including the govt) for fear of contagion…

This is despite to date only 10 people in HK have been confirmed cases. The status at the time of writing looks like this:

Figure 1: current outbreak statistics

If you look at the numbers, however, the situation is perhaps much less frightening than the media (and officials) have whipped up:

1) Death rate similar/weaker than normal flu? As table below shows, the death rate of diagnosed cases in the epicentre, Wuhan, may be high at 5.7%, but by the time you look at the province at large, it drops to 3.5%, and overall China-wide, the ratio becomes a low 2.2%. HK’s death rate is a lucky big Zero:

Table 1: WARS statistics

Compared to other headline flu pandemics reported (see FR1 below), where death rate range around 0.03-0.08% of population, the current rate of death, even in Wuhan, is a tiny fraction (see right column in Table 1, at 0.0012%) – ie there needs a 100-300x increase in deaths from current Hubei levels (0.00027%) to match past pandemics alone – ie. 16k – 49k in casualties in total. Luckily, the Hubei death toll is a low 162 as of today; 

2) The death rate have been dropping – usually the early deaths tend to be more heavily reported/collected as a statistic compared to the actual infected population, while the catching up by the latter leads to a more normalised, actual rate in time (red line below). Public awareness may also put a stop to accelerated growth in death rates, which the blue line below could well be suggesting, falling from 3% to early 2% in the past few days. A consistent departure from the red trajectory will mean we can largely return to normal activities:

Chart 1: death rate tends towards the disease’s true virility in time

3)      Vigilance is ultra-high this time – compared to SARS (when prevention only scaled up after several weeks of casualties), people are armed to the teeth within days, thanks to the magnifying effect of social media and international measures (which are unprecedented – chartered flights to retrieve nationals from China, for example). As a result, the spreading of the disease will likely be much less rapid. Here is a map showing which country to be in with any epidemic outbreak. Not surprisingly, OECD countries come top:

Figure 2: which countries are best prepared for an outbreak?

4)      Possible longer drag than SARS – One feature that does not talked about is the timing of the current outbreak – instead of a March incident like in SARS, we are in January, that means the period of time before it becomes too warm for virus to spread diseases will be longer than during the SARS episode, which ended in June 2003 as temperature rose.

This time round, the outbreak will potentially be lengthened by two months. Hopefully the growth in case numbers (red line in Chart 2 below) will see a tailing off much faster this time compared to SARS (blue line) on increased vigilance.

Chart 2: Case growth rate may decay like the SARS outbreak

5)      Virility tracking will give the answer – the viciousness of the current outbreak has yet to be proven, but if the trends discussed thus far hold, the situation stands good chance stabilising at current levels.

In the next few weeks we should have our answer, but if anyone even remembers the not too distant 2009 avian flu outbreak, which is so far 1000x higher than WARS in death rates (red dotted line, Chart 3), people seem much more ready, if not more than necessarily prepared this time round.

Chart 3: log chart comparing current death rates to past pandemics

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Reference – further reading 1 (FR1)

Flu causes more death than you may think!

Every flu season, a lot of people die from this disease, mainly from complications such as pneumonia

More than 200,000 people are hospitalized each year in the United States for the flu illness and its complications and between 3,000 and 49,000 people die each year from the flu. The number of flu deaths every year varies. That is 1.5%-25% of hospitalised flu victims die each year!

According to the World Health Organization (WHO), about 3 to 5 million cases of severe flu illness and about 250 000 to 500 000 flu season deaths worldwide occur due to the influenza virus. That is anywhere between 5% to 17% of deaths.

Really big pandemics in context

The world has seen five pandemics during the last century, which took a large number of lives. Here are the figures of deaths that occurred in the United States and Worldwide during those years.

1. 1889 Russian Flu Pandemic – about 1 million flu deaths (0.07% global population)

2. “Spanish flu” A of 1918-19 caused the highest number of influenza-related deaths: approximately 500,000 deaths occurred in the U.S. and 20 million worldwide. That figure is more than the total number of deaths caused by the World War one — 16 million. As a matter of fact, during that year, the flu had killed more people than any other illness in recorded history. (1.1% global population)

3. “Asian flu” A of 1957-58 caused 70,000 deaths in the United States and about one million to two million deaths worldwide (0.07% global population)

4. “Hong-Kong flu” A of 1968-69 resulted in 34,000 deaths in the United States and an estimated one million to three million people died worldwide. (0.08% global population)

5. 2009 H1N1 Flu Pandemic – about 18,300 deaths in the United States and up to 203,000 deaths worldwide (0.003% global population)

So amongst the most feared pandemics in history, only the Spanish flu was of truly frightful scale when 1.1% of population perished.

https://healthvigil.com/flu-season-deaths-us-worlswide/

Reference – further reading 2 (FR2)
Trends in Recorded Influenza Mortality: United States, 1900–2004, by Peter Doshi

In results section author concluded: “An overall and substantial decline in influenza-classed mortality was observed during the 20th century, from an average seasonal rate of 10.2 deaths per 100 000 population in the 1940s to 0.56 per 100 000 by the 1990s. The 1918–1919 pandemic stands out as an exceptional outlier.”