There have been a number of partial extinctions of we humans within the written historical record. The Black Death of 1347-51 killed about a quarter of the Earth’s population. The Little Ice Age of the 16th to the 19th centuries, which followed the Medieval Warm Period, also killed about a quarter of humanity through lack of food. The 1918 Flu epidemic killed as many as 100 million people (about as many as Socialism has killed).

Local epidemics can be much worse. The Cocoliztli epidemic in Mexico in 1545-48 killed 80% of the population. It returned in 1576-80, killing half the population.

Pathogens keep evolving and mutating, creating an ever present threat. And they can make the species jump from other animals, creating totally new human diseases which we have no immunity against. This is what Wuhan Coronavirus is.

It was first noticed that there was a cluster of infections of workers at the Huanan Seafood Wholesale Market on 8 December 2019. Initially the Chinese authorities arrested anyone who publicised it. But on 31 December events were getting out of hand and the Chinese informed the World Heath Organisation. The virus was quickly genetically sequenced and that information was release to the world’s scientists. They named it 2019-nCoV.

So now we know that it is a completely new Coronavirus, just as SARS and MERS are, that has crossed over from the reservoir of the disease that lives in local bat (or maybe snake) population. Both of these were sold at the market.

Now, here are the reasons you should worry:

• The virus kills humans. We don’t know what percentage, because most infections are very recent. But 41 people (as of yesterday) have already died from it.
• It is airborne. Most pathogens you have to ingest. This one is in the air you breathe. It can and is spreading very quickly indeed.
• We have no immunity to the virus because it is new to humanity. So no herd immunity to prevent the spread of the disease, no individual immunity to keep us healthy.
• It has a long, symptomless incubation period, up to 14 days, during which the victim is contagious and spreads the disease. This is incredibly dangerous.
• Modern air travel gives the virus a free ride to the whole planet very quickly. There are already laboratory confirmed cases in Thailand, Hong Kong, Australia, France, Japan, Malaysia, Singapore, Taiwan, Macau, South Korea, United States, Vietnam and Nepal. With unconfirmed cases in several other countries.
• Basic reproduction number (R0) is the number of new cases one infected person generates on average over the course of its infectious period. For Flu it is in the range 2 to 3. For Ebola it is 1.5 to 2.5. For this Coronavirus it is 3.8. So it is highly virulent and spreading exponentially.
• In the last 24 hours there have been more confirmed cases than there were total cases until Wednesday (the 22nd). In the last day there have been more new cases than there were in the first 41 days of the outbreak.
• It will take about 12 months to develop and put into mass production a vaccine. Which itself cannot offer 100% protection.
• There are very few anti viral drugs and they are of patchy efficacy.
• Mutations of the virus have already been detected, making it more difficult to deal with.

There are a number of reasons why this epidemic might already be worse than we think:

• The Chinese secrecy for the first month.
• Videos from Chinese health workers saying that the numbers already infected are far, far higher than stated.
• Videos of victims in China just keeling over in the street, on trains and in supermarkets.
• China has locked down Wuhan and 12 other cities.
• Russia has stopped some of its flights from China.
• A new 1,000 bed hospital is being built in Wuhan. In six days!

So we live in interesting times. This is a genuine existential danger, unlike Greta’s lie based climate panic.