Home > Columnists Updated 18 April 2013 The last battle on earth The last great battle on earth is one we humans could lose. And this invisible enemy could strike any day, says Susan Erasmus. 2 Start A Health24 blog » Try Our quizzes and tools » Follow Health24 on Twitter » Ask CyberShrink » 10 yucky hygiene facts 'Cancer is your fault' The last great battle on earth is one we humans could lose. And this invisible enemy could strike any day, says Susan Erasmus.Modern urban populations are about as vulnerable to pandemic influenzas as they would be to bombings or chemical warfare. In fact, the danger is probably much greater.In many developed and developing countries we have quite a touching faith in the medical professionals' ability to save lives. And they do. But it's one thing being in a car accident, or having some rare condition or infection – and quite another being one of millions of people in the same city coming down with the same airborne killer virus at the same time. In our lifetimes most of us haven't faced anything like that.I hope we never will, but it could happen, and it could happen soon and swiftly.A killer plagueIn fact, we have no perception of what people went through in 1918, or in the times of the Bubonic Plague, when millions of people died. Whole villages were wiped out in a few days. Estimates of deaths during the 1918 flu epidemic range from 50 – 100 million. Twenty million people (mostly soldiers) died during the First World War to put it into perspective.Of course, the war contributed to the vulnerability of people to this deadly flu. Many people were malnourished after years of war depleted food reserves, the living conditions in barracks were insanitary, ships and trenches were unhealthy and overcrowded. Also, the virus was spread very swiftly with soldiers returning from the arena of war to their homes across the world in 1918. Train travel and boat trips were becoming more common and the virus initially seemed to follow these travel routes, even in South Africa, where it is estimated almost two million people died. It didn't kill the usual victims – young children, elderly people, people with lung problems or weakened immune systems: it killed the young and the vigorous in their millions.This was an avian or bird flu, much like the one currently doing the rounds in China, called by the very clinical sounding name H7N9. Scientists found the body of a woman who died from the 1918 flu who was buried in the permafrost in Alaska and they were able to identify the virus's genetic sequence using her tissue samples.Normal flu vs. avian fluSo what's the difference between a bird flu and the normal flu that does the rounds every year? Well, in short, the first one is mostly lethal, and the other is mostly not. Flu strains constantly mutate, which is why last year's flu shot won't protect you this coming winter. But the big danger is that a viral infection can 'jump' from vertebrate animals to humans, and combine with an existing flu virus and thus become airborne and highly contagious. Humans have almost no immunity against diseases or infections from animals (called zoonoses), mostly spread by direct contact between animals and humans. Initial outbreaks of diseases such as measles when they were first transmitted to human populations were often fatal. Think of something such as smallpox and the devastation it caused to indigenous populations of countries such as the US and South Africa. In many areas it killed up to 90% of people.And of course, in our modern times massive disease outbreaks are helped by overpopulated, polluted and insanitary megacities, overcrowded public transport, office air conditioning systems and large gatherings of people in confined spaces such as sports stadiums. Such large, high density populations are a largely modern phenomenon. We don't really know what the effects of a massive pandemic would be in a city of 12 million people. At best, the experts can play the guessing game.What about antibiotics?We place our hope in vaccinations and antibiotics. Vaccinations as preventative mechanisms and antibiotics to deal with secondary bacterial infections caused by the virus. But an avian flu can often spread faster than vaccines can be manufactured or distributed. Even if you could lay your hands on precious antibiotics, many people have abused these to such an extent for minor complaints that they might not work when you really need them to. Or unfinished courses of tablets could be the cause of revitalised germs doing the rounds.Am I just being a scaremonger? I wish I were. There's a reason why people get hysterical when a new bird flu kills sixteen people in China – and it's not just to fill newspapers and news websites. With modern transport, the virus can move across the world in twelve hours, finding vast new unprotected populations to infect. And if it's anything like the 1918 virus, you could be merrily sweeping your floor on Thursday morning and be dead by Friday night.So what do I suggest? People can't stop travelling, or return to a rural hunter-gatherer lifestyle, or start living like hermits. We need to accept that epidemics are the price we pay for crowded communal living, farming with animals, and just being human. To name but a few.All you can do is to keep healthy, not abuse antibiotics, cross your fingers, wash your hands and hope for the best. We live on a precarious planet and by far the biggest wars we will ever fight will not be with each other, but with invisible bacteria and viruses. And a new vicious strain of bird flu could be humanity's Armageddon.(Health24, World Health Organization, foreignaffairs.com, Bloomberg.com) Susan Erasmus Susan Erasmus is the deputy editor of Health24. Read more of her columns . More in Columnists More by Cybershrink More: Columnists advertisement Read Health24’s Comments Policy Comment on this story 2 comments Comments have been closed for this article. Logout Comment 0 characters remaining Share on Facebook Loading comments... From our sponsors Why probiotics are beneficial for IBS Hearing aids on a windy day? No problem! A step-by-step guide on how to do pelvic floor exercises correctly Live healthier Get rid of lice! » Toddler dies after DIY lice treatment Back-to-school head lice Comb out head lice 20 head lice myths debunked Head lice are tiny, wingless insects that live in human hair. They cannot fly, jump or swim and are spread by head-to-head contact. Check out this infographic to learn more. 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