----- Forwarded message from Eric Lerner <elernerat_private> ----- From: Eric Lerner <elernerat_private> Subject: SARS: statistical evidence for secondary infection To: politech Date: Tue, 06 May 2003 22:53:26 -0400 X-Mailer: Mozilla 4.78 [en] (Win98; U) I would like to call attention to evidence that, it seems to me, points strongly to the existence of a secondary infectious agent being responsible for the deaths from SARS. I am researching a feature article on the search for the cause of SARS and did a statistical analysis of SARS cases and deaths. As I am also a research physicist, I am experienced in analyzing time series data. The point I raise may be obvious, but I have not seen it mentioned in the press or on the web, so I pass it along in the chance that it has been overlooked. I was struck by the fact that both the number of SARS cases and the number of SARS deaths lie extremely close to a simple exponential growth rate curve. But the exponential rate of growth of the deaths is VERY different than that for the cases. Using WHO data for the last month, the rate of growth of the caseload is 40% per 10 days, while the rate of growth of the number of deaths is 78% per ten days. The death curve lies remarkably close to an exponential curve, with most points within 5% of the curve. Extrapolating the curve backwards, the Feb. 11 report by the Chinese authorities of 5 deaths on that date also lies on the curve. In addition to the very different growth rates, the case curve and the death curve do not intersect the axis at the same date, indicating different index cases. For the case load, the first case, extrapolating backwards, would be Aug.1 ,2002, but for the deaths, the first case would be Jan. 1, 2003 (assuming the first death to come 14 days after that case started.) If the data for China alone is used, the deviations are greater, as there is an admitted understatement of cases and deaths in the period before April 20, but the general pattern is very similar. Using the Feb. 11 estimate of 300 cases and 5 deaths, the growth rate of cases in China is 38% per 10 days and of deaths 58% per ten days. (The rate of increase of death is identical if only the last month of data is used.) The index case from the case curve would be Aug. 10, 2002 and from the death curve Jan.5, 2003. This data is very consistent with an initial, non-fatal infection starting in August, and a secondary infection by a different organism, with high mortality rate, starting in January. By comparing weekly number of deaths with weekly cases two weeks earlier, it appears that such a secondary infection has a mortality rate of at least 25% and spreads much more rapidly that the SARS infection itself, perhaps by a different method. The widely noted increase in the mortality rate of SARS would then be seen to be a consequence of the spread of the secondary infection, with more and more of total SARS patients now having the deadly secondary infection. This would also explain why patients are showing up in India and Canada with SARS coronavirus infection, but no symptoms--they have not been infected by the secondary infection organism. The data seems to indicate a secondly infection, which requires the SARS infection first, not a mutation of the SARS virus. Since the secondary infection, or whatever causes the deaths, is spreading far more rapidly than the basic SARS infection, if it was an independent cause of the sysmtpoms, the case load would also begin to increase more rapidly. In Hong Kong, this certainly does not seem to be the case, as death as a percentage of two-week-old cases are still rising rapidly, while the overall level of SARS cases declines. But this behavior would be very consistent with a secondary infection which can only spread among those who already have the initial SARS virus. I admit that the Canadian results, which show the SARS virus positive tests declining with time could indicate the more pessimistic alternative, that the secondary infection can spread on its own, without prior infection by the SARS coronavirus. However, in Hong Kong they appear to be getting positive coronavirus tests from all SARS patients. If this hypothesis is valid, there should be an infectious agent that shows up only in SARS dead and in those who become very sick and need ventilators(who presumably would die without treatment). Also, it implies that death rates will rise in mainland China until they reach the levels of Hong Kong, which is nearly 25%. Eric Lerner Lawrenceville Plasma Physics elernerat_private ----- End forwarded message ----- ------------------------------------------------------------------------- POLITECH -- Declan McCullagh's politics and technology mailing list You may redistribute this message freely if you include this notice. ------------------------------------------------------------------------- To subscribe to Politech: http://www.politechbot.com/info/subscribe.html This message is archived at http://www.politechbot.com/ Declan McCullagh's photographs are at http://www.mccullagh.org/ Like Politech? Make a donation here: http://www.politechbot.com/donate/ -------------------------------------------------------------------------
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