X-Message-Number: 21432 Date: Thu, 20 Mar 2003 02:52:21 -0500 (EST) From: Charles Platt <> Subject: Some SARS numbers Initially the number of cases of a totally new infectious disease tends to grow at an exponential rate, as each new patient infects a number of new patients, who infect more patients, and so on, while the medical community scrambles to catch up. Eventually the outbreak is contained (e.g. by a strict quarantine policy), or a cure is found, or the virus uses up all the potential victims. At this point the exponential curve turns into the S curve that is familiar in many demographic phenomena. The big question is how long we have to wait before the growth in SARS cases (which currently appears to be exponential) levels off. I will be tracking the number of announced cases during the next week or two in an effort to determine whether SARS is still in the exponential growth phase. Based on very fragmentary evidence, some from CDC, some from WHO, and some from an ICU doctor in the Price of Wales hospital in Hong Kong, I will assume tentatively that the average incubation period for SARS is about 5 days, and the average patient infects three new patients. In the US, assuming we have 10 patients currently, the initial exponential growth looks like this, assuming that a new patient does not become contagious until the end of the 5-day incubation period (which may not in fact be true): 5 days 30 patients 10 days 90 patients 15 days 270 patients 20 days 800 approx patients 25 days 2400 approx patients 30 days 7200 approx patients 35 days 21600 approx patients 40 days 65000 approx patients 45 days 200000 approx patients Thus some time by mid-May we would expect to see about 1 person in 1000 infected in the USA. Now of course we may hope to see successful efforts at containment before then. The trouble is, this virus(?) appears to be highly contagious, contrary to news reports. So far as we know, at least two people in Hong Kong caught it merely by sharing a hotel elevator briefly with an infected person. Also the relatively long incubation period means that by the time someone has been diagnosed, probably (s)he has had time to infect more victims, who will not be identified until another five days have passed. Antiviral drugs may be effective, but their supply is limited, and I find it hard to see how supplies can be ramped up at an exponential rate proportionate with the rate of contagion. Also the most appropriate antiviral drug in the United States can be prescribed only for Hepatitis C, as a result of FDA restrictions. Simple precautions by individuals may be more effective, such as wearing masks and gloves. Expect masks to be as prevalent on the NY subway as they are on the Tokyo subway, within a month. As for mortality, the current figures are artifically low because many "survivors" are being ventilated (oxygen forcibly administered via endotrachial tube), and if the experiences in Hong Kong are any guide, weaning people from the ventilators is problematic. Thus the patients who are still alive may not stay alive. They are not, apparently, "getting better" in the simple sense. Moreover this virus appears to afflict young people as well as the elderly. One patient in Hong Kong is a 23-year-old who was in good physical shape before she was infected with SARS. Consequently I am concerned about the immediate future. Personally I live in a remote area where I can easily be self-sufficient in every respect for 6 months or so. But by the end of that time, I will be forced to rejoin society, where I believe the virus will be still active. Also I think it is likely that at least one cryonics member will contract this disease. Personally I question whether standby team members should participate in that case, so long as the mode of transmission of the virus is not fully understood and we do not know whether precautions provide protection. I do not believe it is reasonable for any transport team member to participate if there is a very high mortality risk. We have handled HIV-positive patients and patients suffering hepatitis C, but SARS looks much worse. Not only the standby team members, but the cryonics organization itself will be endangered if a large number of key personnel are wiped out. In any case a hospital may simply refuse to allow a SARS patient to be taken for cryopreservation. Autopsy will be inevitable during the early spread of this disease. Currently there is a lot of conjecture. The virus may turn out to be less infectious that I am suggesting. The medical community may do a fine job of isolating cases. But in cryonics, where we are always weighing risks, it doesn't hurt to make contingency plans. As a first step, I have asked Larry Johnson, Alcor's new director of clinical services, to order some really effective masks with HEPA filters. In conjunction with eye protection, gowns, and gloves, this may enable us to deal with SARS cases. Naturally I hope very much that my rather grim concerns are proven groundless. Currently, it is too early to tell. --Charles Platt Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=21432