Apr 27, 2009
Swine flu has been labelled as the next major disease pandemic. It appears to have emerged in Mexico has possibly killed more than 100 people and infected a few thousand, most of whom have recovered, incidentally. Cases and suspected cases have now been identified in the USA, New Zealand, France, Scotland, Israel, Spain, and elsewhere (see the swine flu outbreak Google Map).
In Sciencebase on April 26, I offered answers to some of the frequently asked questions that have arisen about swine flu, and today am providing an updated FAQ in response to the comments received and concerns raised elsewhere.
How many people have died from swine flu?
In the current outbreak of swine flu as of April 27, just 20 deaths of 103 suspected fatal cases have actually been confirmed as having been caused by the new virus. That’s a lethality rate of just over 1%. Spanish Flu in 1918 supposedly had a mortality rate of 2.5%*. It is in epidemic conditions difficult to disentangle cause of death, pneumonia or other secondary infections might be to blame.
How many people are infected?
Cases in Mexico number around 1600, according to Mexican Health Secretary Jose Angel Cordova.
Is this swine flu the same strain of flu that killed millions in 1918, the so-called Spanish flu?
No. The present strain is a type A influenza virus of class H1N1, certainly, but it is a different sub-species. Influenza viruses evolve very rapidly in response to changes in the immune systems of their hosts.
What does H1N1 mean?
The “H” refers to the viral hemagglutinin protein, and the “N” refers to the neuraminidase protein (enzyme). There are H1N2, H3N1, H3N2, and H2N3 strains of swine flu endemic in pig populations.
Whatever happened to bird flu?
Strains of avian influenza, or bird flu, are still around, these viruses exist in host species in Asia and potentially elsewhere and could still make the leap to humans at any time. Alternatively, another host species harbouring a different type of virus altogether might emerge at another time.
Influenza viruses can exist endemically in pigs as well as birds and other species. The current strain of interest, swine flu, is endemic in pig populations in Mexico but has now spread to people. But, influenza viruses are notoriously promiscuous and can rearrange genetic material to produce hybrid strains. An emerging strain that is both virulent, relatively lethal and can be transmitted between people is the one to worry about.
Didn’t we have swine flu before?
Swine flu has been present for years and commonly infects people who work with pigs. An outbreak at the Fort Dix army base killed and hospitalized soldiers there and led to an ill-fated mass-vaccination campaign under President Ford. An outbreak of swine flu happened in the Philipines in 2007. Although there were tragic deaths it did not lead to millions dying as happened with the flu pandemic at the end of WWI. According to A tale of swine flu from 1977: “The killer never came. The fact that it was feared is one of many things to show how little experts understand the flu, and thus how shaky are the health initiatives launched in its name. What influenza needs, above all, is research.”
Was the new swine flu genetically engineered as a bioweapon?
It is perhaps possible to engineer a virus, but the precursors to this present strain of influenza has been seen in the wild for years and so it would seem highly unlikely that it was synthesised. Is there a lab that could synthesise a whole new viable viral species from combined segments of human, bird, and pig influenza viruses?
But how did porcine, avian, and human viruses get mixed together?
These flu viruses have a segmented genome containing eight pieces of RNA. If two strains infect a single cell their progeny undergo reassortment so that new strains emerge. Pigs are a particularly good biological mixing bowl for flu viruses, it takes just one lucky reassortment that can infect humans to then make the species leap. This has happened several times in the past.
What is WHO doing about the outbreak?
The World Health Organisation will meet in Geneva on Tuesday (April 28) to discuss whether to raise the pandemic alert level. UPDATE: It did and raised to Phase IV (Phase VI is highest). Later it upgraded to Phase V.
Has Europe been affected?
The first case of swine flu has been tested positive in Spain and the European Union is advising citizens to avoid unnecessary travel to Mexico and the USA. Cases in Scotland, Germany and Israel have now been confirmed.
Will a face mask protect me from flu?
Doubtful. If someone is infected and has come into contact, sneezed, or coughed on door handles you touch, food you eat, hands you shake, the mask won’t protect you. What a mask can do is reduce the amount of contaminated droplets of spittle you might spread if you are infected.
What is a pandemic, it sounds scary?
The word pandemic usually refers to the distribution of a disease, in this case H1N1. It simply means an epidemic that has spread beyond a single geographical region to cover all regions within any defined area. WHO says we are the verge of a disease pandemic on a global scale. I.e. an epidemic that is worldwide.
The words pandemic and epidemic have Greek etymology. Pandemic means “pertaining to all people”. “pan” means “all”, “demos” means “people”. The “epi” prefix in epidemic means “among”, so suggesting some kind of localisation.
*Footnote on mortality rates. The often-quoted mortality rate of the 1918-9 pandemic is 2.5%, but most researchers agree that between 50 and 100 million people died during that outbreak. The world population was 1.8 billion at the time, so wouldn’t the overall world mortality rate have been between 3 and 5%, not 2.5%?