Most people think of influenza as nothing more than a bad cold. Nothing could be further from the truth. Influenza is a highly contagious air-borne disease caused by a virus that mutates rapidly, thereby rendering most vaccines obsolete within a short period. Some strains are also highly lethal. The 1918 influenza pandemic (sometimes referred to as Spanish Flu) killed an estimated 30 to 50 million people worldwide within a few months, with some estimates as high as 100 million. To put this into context, the total number of battlefield fatalities in World War I in the previous 4 years was about 9 million with a further 6 million deaths amongst civilians (i.e. a total of 15 million).
Having spent the last 12 years keeping a close watch in Southeast Asia for signs that H5N1 Avian Flu could mutate into a form that could be transmitted person to person, focus has suddenly switched to the other side of the world with news this weekend of an outbreak of Swine Flu in Mexico that as of today (Monday 27th April, 2009) has caused over 100 deaths. The outbreak is caused by a new mutation that combines human H1N1 strains with DNA from an avian strain plus two different swine variants. Who or what was simultaneously co-infected by all these strains to provide a genetic ‘mixing bowl’ is at present anyone’s guess. Unlike Avian H5N1, the new strain can be transmitted person to person. The case fatality rate in Mexico is 7-8 percent. This is ‘only’ about one tenth of that reported Avian H5N1 infection in Southeast Asia. It may also be an overestimate due to possible under-counting of unreported milder cases. However, it is still a fearful threat. To put it in context, some estimates put the case fatality rate of the 1918 Spanish Flu as low as 2.5 percent. Also, like the Spanish Flu, and unlike most ‘normal’ flu outbreaks which target infants and the elderly, the new Mexican variant seems to target young healthy adults.
So far cases have also been confirmed in the United States, Canada and Spain, but so far no deaths have been reported outside Mexico. It is believed to take a milder course in these countries, suggesting that there may be some unidentified co-infection in Mexico. One piece of good news is that the virus responds to oseltamivir (Tamiflu) and zanamivir (Relenza), although not to amantadine or remantadine.
Given that the outbreak has already been reported in multiple locations, and given that it is highly contagious, the prospects for preventing a global pandemic do not look good. The British public health authorities were reported as saying it could be here (i.e. UK) in 4 to 6 weeks.