COVID-19 and the great Chinese puzzle (How deep is the corona infection in China really?)

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 COVID-19 and the great Chinese puzzle (How deep is the corona infection in China really?)

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• Wildfire pandemic: What started small in Wuhan, China in November 2019, has gripped the whole world. The speed is mind-boggling, and everyone is petrified.
• Technical clarity: There are 3 things - being infected, being diseased, and being infected + diseased. The virus is SARS-CoV-2 and the disease is COVID-19.

1. The infection and diseases must not be mixed, else wrong decisions happen.
2. The chain is -- get infected - get COVID-19 symptoms - develop pneumonia - die.

• Scale of trouble: In China, 3100 died from at least 81600 confirmed infections. So fatality rate was 3.7%.

1. All diseased were infected, but not all infected died.
2. Not all infected were sick or tested.
3. The kind of numbers from China aren't helpful in assessing the trouble elsewhere.
4. Now China is reporting a stop of virus spread.
5. China is now also trying to prevent spread from returning citizens (from abroad)

• The mathematical puzzle: So 90000 infected in China's 140 crore population makes it a rate of 0.0065%.

1. For any pandemic, its sudden stop due to herd immunity will require 70% infected and immune
2. That will make every second person a dead end for the virus (for spreading)
3. If China claims a stop in spread, then 0.0065% is too low a number. If 70% China was infected, it would be 98 crore infections. The range is too big, and dangerous.

• From start to date: The first doctor(s) who alerted others about the possibility of a new epidemic were all silenced. The first 41 cases all came from Hunan Seafood Wholesale Market, Wuhan. It was closed by 31-Dec, 2019, as WHO also was alerted. Infection was zoonosis - vertebrate to human transmission of infection)

1. Full genome sequence of new virus was mapped quickly and data given publicly
2. The virus was re-named SARS-CoV-2 as it was similar to SARS coronavirus
3. By 15 Jan, COVID spread everywhere
4. From zoonosis, it became anthroponosis (person to person transmission of infection)
5. The question is - when did Wuhan see the first outbreak exactly? Many details are unknown.

• First death: The first COVID death was on Jan 11, 2020 in China, but earlier deaths may simply have been not recorded at all. By 30 Jan, China saw COVID in all 31 provinces. The pandemic was spreading uncontrolled by February 2020.

1. But WHO declared it on 11 March, 2020, perhaps misled by the 0.0065% number.
2. India too was misled due to this non-declaration of an official pandemic.
3. India invoked the Epidemic Diseases Act in March, out of sheer fear of seeing no preparation for a massive outbreak.

• How much has it spread: Disease specialists (Epidemiologists) estimate the transmissibility of SARS-CoV-2.

1. Reproduction Number (Ro) is the number of new infections an already infected person can seed during infective period, provided all contacts were non-immune
2. For COVID virus, Ro is between 1.5 to 3.5.
3. If Ro = 2, then one infected person will infect 2 more, and then 4, 8, 16, 32 ...
4. A large number then turns immune, and scene changes. A newly infected person meets immune people now, and only a few non-immune, and things slow down.

• Scope outside China: This virus may touch 30-70% of world population (of 780 crores). 80% of these won't get very ill, but 14% would. Nearly 6% will need full care. Now China has reported only 90000 cases. The truth may be close to 98 crore. It is clear no country can handle this. So if less than 1% led to a stop of spread, India can be very happy. (but is it true?)
• The other side: The truth may be that although 98 crore were infected in China by March, but only 90000 developed COVID-19. That is 0.0092%. The only way to know the truth is by careful antibody prevalence surveys. So if China locked down much later, then the infection is far more widespread than China knows (or does not know).
• Other countries: Be warned. Expect upto 70% infections in first wave of epidemic. Summers may help, but that is not clear yet. Once the first wave is over, this virus will stay on in human society as a seasonal endemic disease.
• Summary : China may not know the exact extent of the virus's spread inside China, due to late clampdown, or it may know it and is hiding the same.

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