Box 1. HIV a '9' on Richter scale of viral diseases

From the following article:

Mission now possible for AIDS fund

Peter Hale, Malegapuru William Makgoba, Michael H. Merson, Thomas C. Quinn, Douglas D. Richman, Stefano Vella, Fred Wabwire-Mangen, Simon Wain-Hobson and Robin A. Weiss

Nature 412, 271-272(19 July 2001)

doi:10.1038/35085650

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HIV is, without doubt, the 'big one'. This virological 'Richter' scale ranks viruses in the same way as earthquakes. The figure is based on a log10 scale, where 10 represents all deaths worldwide from infectious diseases in 1999. HIV registers a 9.1. For HIV, 23 million people have already died, 36 million are incubating the virus, and 5 million are newly infected each year. More than 3 million will die this year, mostly in sub-Saharan Africa.

Mission now possible for AIDS fund 

The only viruses that have come close to this doomsday scale are the Spanish influenza that killed more than 20 million in the 1918–19 pandemic, and smallpox, which has now been eradicated. Today, hepatitis B and C are major causes of liver disease and cancer, collectively ranking 8.7 in terms of deaths. An effective vaccine against hepatitis B is being introduced worldwide.

Several orders of magnitude lower are dengue fever and polio. In the 1950s, polio caused a great scare in the West. An endemic virus, it might have ranked 6.5 at the time. Large-scale vaccination programmes in its last few regional hold-outs, mainly central Africa and India, mean that the conquest of poliovirus is within reach. Ebola ranks a 3 at most; although frightening, it does not seem to travel well. The West Nile and Hanta viruses, both of which made front-page news in the United States, barely cause a ripple on the scale. A death from Ebola is as great a loss as one from HIV, but in terms of public health it is madness to lose sight of the big ones.

Of all infectious diseases, HIV is the only one that has skyrocketed from nowhere to more than 60 million infections in around 30 years. Given its sexual transmission among young adults, its highest prevalence among the poorest nations of the world, the cost of antiviral medicines, and the lack of a vaccine, there is no let-up in sight. There is nothing to suggest that HIV will plateau, or that it will not reach one billion cases before 2050. It is unlikely, but not impossible, that HIV could attenuate itself, but when and at what human toll? Nobody has any idea. Intervention must be on the same massive scale as the magnitude of the epidemic.

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