The flu virus that nearly killed me
Blood is one of our most precious assets, a carrier of oxygen and of antibodies that protect us against infection - and can also be used to tell stories about our past, says Michael Mosley.
In December, I gave some of my blood to Dr Steven Riley at Imperial College, London. He sent it to a laboratory in China where they hold samples of serums containing every influenza virus to sweep the globe in the past 100 years.
They used this database to see if I had antibodies to particular viruses. A positive match would show that I had, at some point, been infected. I am the first person in the UK to have my blood analysed this way and it told a fascinating tale, with me as a bit player in a far larger drama.
I was born in Calcutta, India, in March 1957, just as a new, deadly strain of influenza virus known as Asian flu emerged from China.
It probably started in a bird, spread to a pig and then infected a human. It reached Calcutta (a port, and therefore a meeting place for people from different countries) in July that year, and nearly killed me.
My mother tells me that I was extremely ill and that for a while it was touch and go. My blood, 55 years on, still shows traces of antibodies, proof that young though I was, I was able to fight it off.
But to this day I have slightly weakened lungs, and chest infections tend to linger. I did recover, but many others in India and the wider world were less fortunate - nearly two million people died.
The Asian flu of 1957 was the first new strain of influenza virus to emerge and ravage the world since the dreadful Spanish flu pandemic of 1918. Asian flu is also known as H2N2, named after a couple of proteins on its surface (haemagglutinin and neuraminidase).
When we are infected by a new virus, our body first has to identify the invader as foreign, then mount an aggressive immune response.
Once our body has learned to recognise the virus surface proteins, it remembers them - which means our immune system is much better prepared the next time we encounter a similar virus.
The problem is that flu viruses mutate rapidly and these proteins change. When that happens, our immune system has to start the whole complicated process of mounting an immune response all over again.
Asian flu, bad though it was, had nothing like the impact of its predecessor. Spanish flu (H1N1) - spread by soldiers returning home from WWI - is estimated to have killed between 40 and 100 million people, making it the greatest infectious catastrophe since the Black Death.
It reached the remotest parts of the globe and in some communities it killed up to a third of the population. So great were the numbers of the dead that in some countries the bodies had to be taken away by the trainload. Spanish flu did, however, galvanise research into vaccines, which has been going on ever since.
After Spanish flu in 1918 and Asian flu in 1957, there was another pandemic, Hong Kong flu (H3N2) in 1968. I was living in Hong Kong at the time, an 11-year-old child, and again my blood shows I was infected. This outbreak was relatively benign, killing "only" about a million people.
The final great epidemic of the 20th Century was Russian flu, which hit Britain in 1977. I was a student at Oxford University and surprise, surprise, my blood shows I got it. People who live in institutions, such as a university, school or hospital, are particularly prone to getting any new strain that is circulating.
Russian flu, however, was not really new. It was actually the re-emergence of Spanish flu or H1N1, which people thought had gone extinct.
No-one knows for sure but it seems likely that H1N1 escaped from a laboratory where it was being studied. Fortunately it seems to have mutated into a more benign form and though it swiftly spread around the globe, this time it did not kill on anything like the same scale.
I don't even remember being particularly ill, though I'm sure it must have caused a lot of disruption at the time. Incidentally it seems to have got the name "Russian flu" as a by-product of the Cold War - there is no good reason to think it originated in Russia.
My immune system then had a relatively quiet time until we started having children, or "virus importers", as they are affectionately known in our house. For about 10 years I got most of the new subtypes that emerged. Now that my kids are older, things seem to have calmed down.
There have been no new seriously lethal epidemics since 1977, but the experts think it is just a matter of time. A new mutant strain may, even as I write, be gestating in a bird or pig somewhere on the planet.
The scientists I've spoken to are confident that what we have learnt from previous epidemics will ensure that the next will be nothing like as bad as, for example, Spanish flu. I hope they are right.
Winter Viruses and How to Beat Them on BBC Two at 21:00 GMT on Monday 28 January, or catch up with iPlayer