Recent research on the 1918 Spanish flu epidemic published February 5, 2004, in ScienceExpress, the online version of the journal Science confirms our worse fears as it suggests that it may have started in birds. The 1918 influenza epidemic killed an estimated 20 million to 40 million people around the world, including at least 500,000 in the United States. The research was the result of a long-term collaboration between the late Don Wiley, a Howard Hughes Medical Institute investigator at Harvard University and Sir John Skehel of the Medical Research Council's National Institute for Medical Research in London.
The findings have at last revealed the mechanism by which the killer flu infected human cells and became responsible for the deaths of many millions of young people as many of the older population had developed some immunity to a similar virus earlier in their lives. The Spanish flu virus is now extinct, but the researchers were able to study its viral DNA sequences by examining biopsies from infected tissues from the bodies of American soldiers who died in the pandemic and an Intuit woman whose body was preserved in the permafrost of Alaska. The scientists used X-ray crystallography to reveal the three-dimensional structure of the 1918 virus' surface hemagglutinin (HA) protein, a molecule that is known to initiate the first stages of viral infection. The protein binds to receptors on the cell surface and causes pores to open in the human cells, allowing the virus to pass through.
The HA proteins produced by human and bird viruses generally bind to different types of cell receptors, making it very difficult for avian flu strains to infect people and vice versa. The paper revealed how this HA molecule could still resemble the avian binding site, but infect humans as the researchers found that two sides of the hemagglutinin receptor-binding site were in slightly different positions in the 1918 hemagglutinin, in comparison with the Hong Kong protein, allowing the human receptor to bind in an antigenically favourable way. This means that during the 1918 pandemic, the HA protein of an avian flu appears to have mutated, allowing the virus to bind with deadly efficiency to human cells, while retaining the basic properties of the avian virus from which it evolved.
While some scientists have long argued the Spanish flu had nothing to do with birds, many others suspected that it was an avian flu virus, which had somehow mutated and "jumped" from birds to humans. The findings of the paper are more important as a strain of bird flu, known as H5N1, has recently been spreading like wildfire across Asia and has already killed 12 people. The hemagglutinin in the 1918 virus has been designated H1, the Asian influenza that began in 1957 H2, and the Hong Kong strain, which began in 1968, H3.
It is understood that many scientists consider that it has the potential to become pandemic in humans if it is not stopped quickly. The WHO, the UNFAO, and the World Organisation for Animal Health have now jointly issued an urgent plea for funding to halt the new bird flu, which they say could quickly evolve into "an efficient and dangerous human pathogen". Many Asian countries have employed mass culling of infected poultry flocks as the best way to control the potential pandemic spread. This radical program has been influenced by a widespread feeling that health authorities in Asia failed to act quickly enough last year to contain the SARS virus, a hitherto unknown human pathogen, which eventually killed about 800 people. Besides being highly contagious, flu viruses have the ability to mutate quickly by exchanging genes with each other, so if someone carrying a human flu virus catches the new bird flu, the two strains can combine inside a patient's body, creating a new, highly contagious and lethal human plague. It is also known that the two flu pandemics of 1957 and 1968 were caused by human and animal viruses mingling to form hybrids.
Thankfully, as with the 1997 outbreak in Hong Kong, nearly all the patient's who have been infected to date by H5N1 seem to have got the contagion from direct contact with infected birds. I am aware of the growing concern surrounding two sisters who died of the disease in Vietnam last month who probably caught it from their brother. There was also concern over a five-year-old girl who contracted the disease on December 7th 2003 who had played near chickens, but her two small cousins, who were hospitalised less than a week later, had only played near her. The WHO has said that the current outbreak of H5N1 in birds started in South Korea in December but many feel the outbreak probably began a few months earlier in the farms of southern China, where ducks are frequently quartered along with pigs and people.
There is little doubt that like earthquakes in California, another worldwide flu pandemic is "inevitable and probably imminent", however the world is a different place than the impoverished conditions that existed at the end of the First World War. For a start, there is now a global disease-surveillance system to warn us if H5N1 started to show evidence of direct person to person. We have better anti-viral drugs and treatments that were available to the many millions who succumbed to the pandemic during the last century. At best, we can say that present transmission of H5N1 between humans appears to be inefficient as witnessed daily on our television screens by the workers who wore only gloves instead of masks to cull the poultry corpses into barrels.
Another study led by Ian Wilson of the Scripps Research Institute in La Jolla, California, also recently published in Science, confirms that birds were the source of the 1918 strain. Although, there had been no recorded cases of bird flu infecting people until an outbreak of H5N1 among poultry in Hong Kong in 1997, it is now thought that all the worst outbreaks of flu in the past century, including the 1957 Asian flu and the 1968 Hong Kong flu originated from birds.
Most of us remember that in 1997, 6 people died after contact with infected birds and a decision was taken to cull Hong Kong's entire poultry flock of about 1.5m birds in just three days. By denying the flu strain further opportunities to infect humans, this swift action may have prevented a pandemic. Then, let us only hope that we can stop this present outbreak of H5N1 in its tracks before we are facing another world problem.
Centre for Disease Control Background on Pandemics
An influenza pandemic is a global outbreak of influenza and occurs when a new influenza virus emerges, spreads, and causes disease worldwide. Past influenza, pandemics have led to high levels of illness, death, social disruption, and economic loss. There were 3 pandemics in the 20th century. All of them spread worldwide within 1 year of being detected. They are:
1918-19, "Spanish flu," [A (H1N1)], caused the highest number of known flu deaths: more than 500,000 people died in the United States, and 20 million to 50 million people may have died worldwide. Many people died within the first few days after infection and others died of complications soon after. Nearly half of those who died were young, healthy adults.
1957-58, "Asian flu," [A (H2N2)], caused about 70,000 deaths in the United States. First identified in China in late February 1957, the Asian flu spread to the United States by June 1957.
1968-69, "Hong Kong flu," [A (H3N2)], caused approximately 34,000 deaths in the United States. This virus was first detected in Hong Kong in early 1968 and spread to the United States later that year. Type A (H3N2) viruses still circulate today.
