 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Medical Forum / General / General / May 2006Question on influenza mortality rates
The WHO site states the following: "The severity of disease and the number of deaths caused by a pandemic virus vary greatly, and cannot be known prior to the emergence of the virus. During past pandemics, attack rates reached 25-35% of the total population. Under the best circumstances, assuming that the new virus causes mild disease, the world could still experience an estimated 2 million to 7.4 million deaths (projected from data obtained during the 1957 pandemic). Projections for a more virulent virus are much higher. The 1918 pandemic, which was exceptional, killed at least 40 million people. In the USA, the mortality rate during that pandemic was around 2.5%." Given that the human mortality rate for the H5N1 virus is presently greater than 50%, what makes 2.5% reasonable as the upper bound for projections relating to a possible H5N1 outbreak? To a layman such as myself, there is a disconnect here. E >The WHO site states the following: > [quoted text clipped - 15 lines] > >E I think you just misread it. Nothing you quoted says that 2.5% is an upper bound for some future event. It says that is what we observed in 1918, in US. That is the only 2.5% number, at least in the part you quoted above. bob > >The WHO site states the following: > > [quoted text clipped - 22 lines] > > bob Right, but the implication (at least to me) is that if the new flu were to be equivalent in virulence to the 1918 flu, 2.5% mortality would not be an unreasonable guestimate. E >> >The WHO site states the following: >> > [quoted text clipped - 26 lines] >to be equivalent in virulence to the 1918 flu, 2.5% mortality would not >be an unreasonable guestimate. That is a quite different implication than the one you drew the first time, suggesting that this was a worst case number. But if you are looking for implications, the important statement in the segment you quoted is the first sentence. There is no way to know the properties of a new flu virus in advance. bob > >Right, but the implication (at least to me) is that if the new flu were > >to be equivalent in virulence to the 1918 flu, 2.5% mortality would not > >be an unreasonable guestimate. > > That is a quite different implication than the one you drew the first > time, suggesting that this was a worst case number. ... > bob I am missing something here. To me, the WHO is suggesting that the 1918 flu represents a worst case scenario, and that the 2.5% would be consistent with that for a new virus of equal virulence. So that - in effect - 2.5% represents the worst case. Versus 50+%. Both numbers being deaths/known cases. E >> >Right, but the implication (at least to me) is that if the new flu were >> >to be equivalent in virulence to the 1918 flu, 2.5% mortality would not [quoted text clipped - 9 lines] >I am missing something here. To me, the WHO is suggesting that the 1918 >flu represents a worst case scenario, I am mystified why you would think that. Nothing in what you quoted says it is a worst case estimate, and it is hard to imagine why they would present it as such. It is simply a historical "fact" (an estimated fact). >and that the 2.5% would be >consistent with that for a new virus of equal virulence. Now you have read something else in there that was not said. What's this about "equal virulence"?? No one has any clue whether the new virus will be more or less virulent than the 1918 virus. Now, it might be interesting to wonder what would happen if the exact same 1918 virus came back -- obviously an example of same virulence. The world is smaller now, so it might well spread faster and further. (Remember, flu is spread by those who do not yet know they have it.) Is our medical care re flu better now, as a factor in the other direction? Interesting question. I think that is why public health officials are trying to figure out how to respond. Whether the current bird flu virus becomes a problem, some flu will at some point. The planning is a good idea. >So that - in >effect - 2.5% represents the worst case. I think you are just reading too much into what you see. There is no reason to think the new virus will be like the old one, or that the old one now would be like the old one then. One can make models that predict any of a wide range of things. With luck, the models offer the public health officials ideas about the best places to fight the new virus. That is, the number from a model is less important than the sensitivity of the model to variables they examine. bob >Versus 50+%. Both numbers >being deaths/known cases. > >E > >I am missing something here. To me, the WHO is suggesting that the 1918 > >flu represents a worst case scenario, [quoted text clipped - 3 lines] > would present it as such. It is simply a historical "fact" (an > estimated fact). I see in the WHO quote a suggestion or implication that you evidently don't see and which I may well be misconstruing. ..... E > The WHO site states the following: > [quoted text clipped - 13 lines] > projections relating to a possible H5N1 outbreak? To a layman such as > myself, there is a disconnect here. Not everyone will get the illness. In addition, the known H5N1 viruses do not spread easily amoung people. And many people may be exposed to the virus, but not get sick. You can learn more about this at: http://www.cdc.gov/flu/avian/index.htm Jeff > E As I understand it (and I could well be wrong) the "mortality rate" equals the number of deaths divided by the number of known cases of sickness. If so, the (many) people who are exposed but do not get sick would not be part of the computation. As far as I know, only persons who actually had the H5N1 are included in the present 50+% mortality rate. I looked at the site you referred to and couldn't find the issue specifically addressed. E >As I understand it (and I could well be wrong) the "mortality rate" >equals the number of deaths divided by the number of known cases of >sickness. yes. >If so, the (many) people who are exposed but do not get sick >would not be part of the computation. As far as I know, only persons >who actually had the H5N1 are included in the present 50+% mortality >rate. yes, and this is a well-known uncertainty. But careful... need to distinguish "exposed" from "had". In this context, it makes a big difference whether the person was exposed but never got the virus, or got it and had a mild case. In principle, one can get better info here by seeing whether people who were probably exposed but did not get ill have antibodies to the virus, a sign they were infected. Unfortunately, this testing is not very likely in the places where the virus is currently an issue. (Anyone know whether any such data have been reported yet?) bob > As I understand it (and I could well be wrong) the "mortality rate" > equals the number of deaths divided by the number of known cases of > sickness. If so, the (many) people who are exposed but do not get sick > would not be part of the computation. As far as I know, only persons > who actually had the H5N1 are included in the present 50+% mortality > rate. That is correct. The mortality rate includes only those who are known to have the illness. IIRC, when they looked for evidence of the infection in the blood (antibodies to the virus), they found that many people were exposed to the virus, but not get sick. In addition, the mortality rate wouldn't include those who were ill from avian flu, but did not know it was bird flu. Jeff > I looked at the site you referred to and couldn't find the issue > specifically addressed. > > E > The WHO site states the following: Deliberate disinformation. The WHO also refuses to share genetic data with scientists, so that is is impossible to know which genes it has aquired or to make a vaccine. More realistic estimations for the death toll of pandemic H5N1 Influenza is 50% gets infected with a CFR of 50%, meaning 25% will die due to the disease itself. an additional 25% will die due to starvation. So it's around 3 billion casualties. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.