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Pandemic’s progress: we saw it coming

Be in no doubt, people in Britain will die from Mexican swine flu and there will be several million

Private Lewis had suffered a sore throat before. He knew that feeling lousy wasn’t a good excuse for not performing to the best of his ability. Against medical advice he joined his fellow US army recruits on their all-night hike, in New Jersey, in January 1976. A few hours later he collapsed. He was carried back to Fort Dix army base but died shortly afterwards. Lewis’s death, from swine flu, provoked nationwide panic of the kind we are already beginning to witness in Mexico and now the United States, where California has declared a state of emergency.

The thought of insidious aliens gnawing away at us from within is, as the new swine flu scare reminds us, terrifying. So just how bad might this pandemic be? Scientists have for several years been saying that a global outbreak of influenza is overdue. But after keeping a fearful eye on the H5N1 strain of avian flu it seems that an H1N1 swine flu strain from Mexico has taken us unawares. Its rapid spread is no surprise. Flu can be astonishingly contagious once it acquires characteristics enabling transmission from human to human in aerosols from coughs and sneezes. H5N1 (which kills one in two infected people) has yet to evolve in this way. Its victims have been predominantly poultry farmers who were in persistent contact with infected birds.

Flu viruses are transmitted as tiny particles containing a collection of RNA fragments, each representing one of the virus’s genes. In order to read this information and generate new viral particles the pathogens must enter living cells (usually in the respiratory tract) and hijack their gene-expression machinery. Eventually a multitude of replica viruses bursts from the cell, destroying it. The efforts of the body to attack the virus can cause even more severe damage. Secondary bacterial pathogens can colonise this impaired respiratory tissue and contribute to our demise.

The influenza virus has an array of tricks that has made it so difficult for us to control. For a start, it is difficult to speak of one single virus. There is a multitude. The terms H5N1, H1N1 and so on refer to small molecules on the viral surface that control their ability to enter and leave host cells. These proteins are recognised by our immune system and we can, in time, generate antibodies that neutralise the virus. However, each H and N variant is quite distinct; antibodies generated against H1 do not recognise H5, for example. Immunity to one strain is not carried to others and, unlike the case for some other viruses – measles, for instance – we can be infected repeatedly by flu throughout life.

Flu viruses are widespread and can infect a multitude of animals (pigs and birds being just two examples). Dozens of distinct H and N types exists. Rarely, two or more different flu viruses might infect the same animal cell at the same time. The RNA gene fragments can mix and reassort to create novel, chimeric viruses. These can carry new properties (for example, airborne transmission and hypervirulence along with a new and previously unrecognised set of surface proteins).

Already, some depressingly predictable examples of infection bigotry have emerged. Several Asian governments have banned imports of Mexican pork, even though there is no evidence that this particular “swine” virus emerged from pigs. Nor can flu be transmitted through meat. On Monday, Indonesia’s health minister won the race to make the standard conspiracy claim of the virus being a man-made bioweapon. Writing in the Guardian, Mike Davis, author of a book on flu, blames the global meat industry while failing to note the regularity with which these pandemics have emerged through history, predating the (albeit disgusting and greed-driven) practices of intensive farming.

Pandemics begin when variants of viruses to which humans have never been exposed before suddenly appear – so no immunity is present within the “herd”. Every time a virus is transmitted to a new human being it can establish an infection, propagate and pass on.

The statistics so far indicate that the “Mexican swine flu” pandemic might be relatively predictable. Dr Paul Digard, a leading research scientist studying the flu virus at Cambridge University, says we may be witnessing the start of a pandemic. The early indications, however, suggest that the virus probably is not hypervirulent. In Mexico, where at the time of writing more than 1,300 infections have been reported along with between seven (confirmed) and 159 (total including unconfirmed) deaths, it would appear that the virus is not hypervirulent. For all of the reported cases, many milder cases have probably gone unreported and that no one has yet died in most other countries where the spread has been traced, such as New Zealand and Israel, supports this. However, at the time of going to press, a 23-month-old child was confirmed to have died of swine flu in the US state of Texas. We may be heading for something like the 1958 or 1967 pandemics, in which a few million died globally (tens of thousands in the UK). This is serious but, mercifully, the virulence appears to be markedly lower than the virus that caused the 1918 flu pandemic, where 50 million or more died globally.

Exhumation of permafrost-preserved cadavers has yielded some of the genetic secrets of the 1918 virus. It was of the H1N1 type, but variants of other genes might have lent it extreme virulence. Efforts are under way to determine whether the Mexican virus (also H1N1) also has those gene variants.

For all our fears of pestilence, we should remember that mankind evolved in an environment of persistent microbial assault. A key driving force behind human diversity has been the necessity to create a spectrum of individuals, each able to resist different microbial onslaughts. It may be of little comfort to afflicted individuals, but as a species, at least, we are resilient.

A typical British citizen today is generally healthier and warmer than 90 years ago. Anti-viral drugs and vaccines can slow viral replication (turning a killer into a mere harmer). The secondary bacterial infections can, at least for the time being, be treated with antibiotics. Even those rather ineffectual-sounding public health measures, such as using disposable hankies to capture viral particles and avoiding crowds, or wearing faces masks, can keep particles out of the respiratory system.

So, 159 already dead in Mexico and one dead in the US. Which way is it going to go? Today, we can’t know. By next week, we should have much more reliable statistics on just how virulent and transmissible this virus really is.

And let’s not forget Private Lewis. He was confirmed as having died from the H1N1 strain, similar to that which had caused the 1918 pandemic. When scores of other army recruits fell ill in New Jersey in 1976, and sporadic cases turned up elsewhere, the American government panicked and implemented a programme of vaccination for the entire population. But it turned out that many of the army recruits had actually contracted a different flu virus and the H1N1 strain never “took off”. The vaccine, however, ended up causing a rare disease, Guillain-Barré syndrome, in thousands of the several million inoculated Americans (35 died). The programme was aborted and public health policy in the US has been shy of such national programmes ever since.

This time, the disease is spreading. It will be a great challenge to see whether technological advances have provided the tools to allow us to intervene. Can we, for example, develop a vaccine quickly enough to thwart the pandemic’s progress? The ability of the virus to transmit is based on probabilities. Flu transmits better during colder weather, when people are huddled together inside crowded Tube trains or buildings. Previous pandemics have tended to proceed slowly in summer, but then intensify in autumn and winter. Nowadays, we can determine the precise genetic sequence of a virus within days and produce a vaccine within months. This means we might be able to intervene this time to prevent this particular virus becoming too deadly in its effects.

People here in Britain will die. But unlike with the financial crash of 2008, we have seen this one coming. The government, so far, is playing it right, and I am confident that we are well positioned to survive even pandemic flu.

Michael Barrett is professor of biochemical parasitology at the University of Glasgow and a contributing editor of the New Statesman

History of Flu Epidemics

1510, 1557 The first large-scale influenza epidemics recorded in Europe.
1580 The first recorded flu pandemic. The virus spread from Russia to Africa and Asia, killing more than 8,000 people and wiping out several Spanish cities.
1889-90 Russian flu. The virus reached North America, Latin America and Asia and killed roughly a million people.
1918-19 Spanish flu. This was the most lethal flu on record. Estimates vary, but the virus killed between 20 and 100 million people (two to five times the number of deaths caused directly by the First World War). It was global, reaching the Arctic and remote Pacific Islands and, unusually, affected young people (aged between 20 and 40) particularly badly. Scientists eventually concluded in 2005 that “Spanish flu” was a strain of bird flu that had spread to human beings.
1957-58 Asian flu. The virus started in China and originally mutated from wild ducks. It then combined with a human strain and killed between one and 1.5 million.
1968-69 Hong Kong flu. The virus started in Hong Kong, then spread across Asia to India and northern Australia. It was carried to the US by troops returning home from Vietnam. In total, it killed between 750,000 and a million people, particularly affecting children under five and middle-aged adults.
1976 Swine flu scare. An outbreak in New Jersey caused President Ford to order a nationwide vaccination programme costing $135m. Forty million Americans were inoculated and there was no epidemic.
1977 Worldwide Russian flu scare. Beginning in northern China, the virus spread rapidly around the world but affected only children and young adults (it is not considered a true “pandemic”).
1997 Bird flu (avian influenza). The virus has killed millions of poultry in Asia, Africa and Europe. When it was first discovered, in Hong Kong, as many as 1.5 million chickens had to be slaughtered in the city. Since 1997, a growing number of human beings have been infected, with 248 deaths in 12 countries to date.

Sophie Elmhirst

This article first appeared in the 04 May 2009 issue of the New Statesman, Flu: Everything you need to know