Comments on: Is the 2009 H1N1 influenza virus more dangerous than we think?

By: Lloyd

Lloyd — Tue, 08 Dec 2009 21:48:53 +0000

I've also read that H1N1 is more severe in pregnant women:
http://bit.ly/7aYIjQ

By: Lloyd

Lloyd — Tue, 08 Dec 2009 13:48:53 +0000

I've also read that H1N1 is more severe in pregnant women:
http://bit.ly/7aYIjQ

By: MWR in Afghanistan

MWR in Afghanistan — Sun, 26 Jul 2009 07:18:32 +0000

You've got to be kidding me… Do you not see the data on the populations being hit hardest by this virus (compared to last year's H1N1)? Last year, we did not see this kind of impact on younger people and far far fewer pregnant women were seen developing severe complications (and death) compared to this year's Pandemic strain. I'm also puzzled by the complete lack of insight on the varied impact this is having on less-developed countries (where there are little or no stocks of antivirals, no ventilators, and sparse ICU services, if any at all).

By: gsgs

gsgs — Thu, 23 Jul 2009 06:09:13 +0000

I'd like to see the curves for estimated CFR by age of mexflu and seasonal H1N1
in one picture so we can compare. x:age, y:CFR

By: h1n1_watcher

h1n1_watcher — Sun, 19 Jul 2009 17:31:13 +0000

Thanks for this well balanced article !

The empirical evidence [i]in the human population[/i] does indeed support that the severity (in terms of CFR) of pandemic H1N1 roughly equals that of seasonal H1N1.

Please take a look at the following two charts published at the US flu surveillance site:

The first chart provides an estimate of the prevalence (i.e. the number of people infected)

[url]http://www.cdc.gov/flu/weekly/weeklyarchives2008-2009/picILI27.htm[/url]

It can be seen that the 'impact' in terms of doctor visits due to the current pandmic wave (i.e. the area under the curve since april 2009) is roughly equal (probably less) than the impact of this years sasonal flu wave.

The second chart

[url]http://www.cdc.gov/flu/weekly/weeklyarchives2008-2009/IPD27.htm[/url]

shows the exact number of pediatric deaths (i.e. fatal cases among persons younger than 18 years)
for recent seasonal flu waves as well as for the current pandemic wave.

As can be clearly seen, the total number of deaths (abou 25) attributed to the pandmic H1N1 (pink bars) is still far less than the number of deaths caused by the seasonal flu wave (green bars) .

So even if we conservatively estimate that we have only seen half the impact of the first pandemic H1N1 wave yet, the number of fatalities is still perfectly in line with the numbers seen during a typical flu season.

Furthermore it is worth mentioning that the "pediatric deaths" statistics is probably much more accurate than the number of total deaths published because of the strict legal requirements in reporting the cause of deaths of children.

Interstingly, novel H1N1 does not seem to be more severe than seasonal flu [i]even if we account for the age shift phenomenon[/i]:
In [1] the number of excess deaths [i]in those under the age of 65[/i] of a typical bad flu season is estimated in the range of about 500-1000.
Now compare this to the 260+ deaths caused by the first pandemic wave so far and conservatively further double the number to about 500 pandemic H1N1 deaths in the first wave, this too suggests that the impact of the first pandemic wave is roughly the same as that of the average seasonal wave, and this even so if we restrict the calculations to the younger-than-65 age group (for seasonal flu, the numbers would be more than ten-fold higher if we included the elderly
65+ age groups)
----------
[1]Lone Simonsen "Pandemic versus Epidemic Influenza Mortality: A Pattern of Changing Age
Distribution"

By: h1n1_watcher

h1n1_watcher — Sun, 19 Jul 2009 17:29:51 +0000

By: Chuck

Chuck — Thu, 16 Jul 2009 19:37:38 +0000

More than 90% of the deaths from seasonal flu are among the frail elderly over 65. Stastically, about the same number of elderly would be carried off by something even if there were no such thing as seasonal flu.

More than 95% of the deaths so far from the 2009 H1N1 flu have been of people under 60 years old. While much has been reported about “underlying conditions”, somone with an underlying condition is only about twice as likely to have a severe case of the pandemic flu as a completely healthy person. Depending on your age and any underlying condition, a person under 60 is anywhere between 20 and 400 times more likely to die of the 2009 H1N1 than of seasonal flu.

By: mdubuque

mdubuque — Thu, 16 Jul 2009 11:58:00 +0000

Yes. I understand their point and your informative rebuttal. Given your credentials, time permitting, it seems to this lay person that they would consider publishing your important caveats about the study in their letters section.

Just a thought.

By: profvrr

profvrr — Thu, 16 Jul 2009 11:49:20 +0000

Nature is prestigious but also known to publish less than stellar
science. The conclusions of the paper, with respect to animals, are
correct. However, in any other year a paper comparing two different
strains of any virus in any animal would not likely be published in
this journal. This happens to be a pandemic strain and a great deal of
publicity can be obtained by publishing about the virus.

By: profvrr

profvrr — Thu, 16 Jul 2009 11:46:20 +0000

Flumist is an FDA approved live influenza virus vaccine that is quite
safe and effective. An infectious attenuated vaccine is produced from
a genetically altered virus, and there is always the possibility of
mutation to a virulent phenotype. But no such 'reversion' has been
observed with Flumist. However, the use of Flumist is far less than
inactivated influenza vaccines for a variety of reasons, including the
need to take it by inhalation and the perception that reversion might
occur. Given the nature of the changes in the Flumist strain,
reversion seems unlikely, but always formally possible. But infectious
vaccines in theory provide more robust and long-lived immunity because
they more accurately duplicate a natural infection with the virus. A
good summary of this issue can be found at http://bit.ly/noN71.

By: profvrr

profvrr — Thu, 16 Jul 2009 11:38:22 +0000

I meant to write 'last season's H1N1 strain'; thank for the
correction. I agree that basing the CFR on current data is faulty; but
I believe the CFR will decrease because it's currently based on
lab-confirmed influenza. The CFR may be higher for specific age groups
but I'm considering only the overall rate. But my main point is that
the authors can't say the 2009 H1N1 strain is more dangerous than we
think based on animal models. The best way is to look at the human
data which should give a clear picture by next season.

By: pandemicfluwatch

pandemicfluwatch — Thu, 16 Jul 2009 04:55:38 +0000

"The results show that the virus is no more virulent than last season’s pandemic strain."

I assume you meant last year's seasonal strain? If so, then I would argue that your conclusion is based on a faulty comparison measure: the raw case-fatality ratio. The age distribution of hospitalization and death implies that this disease is significantly more virulent than seasonal strains, but that many of those in the >60 age group have some protective immunity. In the case of a seasonal flu, we would not normally see such a high incidence of mortality or severe morbidity in (non-infant) children and young adults.

Age-specific mortality and hospitalization among those who are susceptible (largely, but obviously not exclusively, those 60 and under) is probably a better measure for comparing the virulence of these two strains, and using that measure I think it's clear that the pandemic strain is worse.

I'm not trying to imply that this is anything like the monstrous 1918 virus -it isn't. (So far at least.) But while I wholeheartedly agree with you that animal models are often poor predictors of human pathology, and even worse predictors of human epidemiology, I don't think we can fairly say this pandemic strain is the equivalent of a seasonal flu.

By: Is the 2009 H1N1 influenza virus more dangerous than we think? « euraktiva

Is the 2009 H1N1 influenza virus more dangerous than we think? « euraktiva — Thu, 16 Jul 2009 03:42:12 +0000

[...] via Is the 2009 H1N1 influenza virus more dangerous than we think?. [...]

By: mdubuque

mdubuque — Wed, 15 Jul 2009 22:46:26 +0000

Interesting rebuttal. Nature is an extraordinarily prestigious publication.

Would you consider a letter to them explicating your view?

By: Liz788

Liz788 — Wed, 15 Jul 2009 21:55:48 +0000

Another off-top question, sorry: I've heard rumors that some of the H1N1 vaccines could be made using live-attenuated viruses (Thailand seems to be testing this method). Does that indicate that there would be potentially serious side effects or that the vaccine could cause a negative viral reaction/response? I know there is an awful lot of anti-vaccine propaganda out there, so I would like to hear from an expert.

By: barnabydawson

barnabydawson — Wed, 15 Jul 2009 20:03:23 +0000

I don't think we really know what the actual severity is. I've seen two credible estimates with a significantly higher severity than the seasonal flu (0.4% and 0.5% CFR). All other estimates seem to assume that all deaths are detected (which is not the experience of the CDC which typically only detects ~5% of deaths from the seasonal flu).

The claims in the popular press that this swine flu is no more severe than the seasonal flu seem to be based on flu surveilance numbers which are well known to be appalling innacurate when used as estimates.

Furthermore the claim that this disease is less dangerous than the seasonal flu seems to require further justification to me as:

1) This strain is infecting a much younger demographic resulting in a much greater loss of years of life per death.

2) This strain is likely to infect many more people than seasonal flu.

3) 1/3-1/2 of deaths are in healthy adults and about 1/4 have only got asthma.

I think you're right about the animal models. But I think we not only need data from humans but some tolerably good analysis of this data before concluding anything about the severity in humans. I haven't seen a good attempt at estimating the CFR yet.