Written by Ng E-Jay
15 May 2009

I refer to the Straits Times forum letter “Let it in while benign to develop herd immunity” penned by Professor Lee Wei Ling, published on 13 May 2009.

In her letter, Prof Lee argues that it is impossible to prevent the H1N1 influenza virus from entering Singapore, and that temperature screening might be ineffective because at least 30% of patients are asymptomatic, and even those who eventually become symptomatic are infectious for at least the first 24 hours before symptoms appear.

She states that since the virus currently exhibits low morbidity and mortality, but could return in a more virulent form after the warm months of the northern hemisphere, there is merit in exploring the idea of “freely opening our borders to allow the relatively benign H1N1 to come into Singapore and allow our people to develop herd immunity“.

I would like to state my strong objection to Prof Lee Wei Ling’s suggestion.

Firstly, there is the common misconception perpetrated by the media and even by healthcare professionals that statistics have proven that the H1N1 influenza virus is more benign than the common flu (see here for example). The statistics have allowed no such conclusion thus far.

According to an article by the Latin American Herald Tribune, the number of deaths in Mexico caused by the swine-flu epidemic have risen to close to 60, while the total number of patients suffering from the disease have crossed the 2,000 mark. Hence, the fatality rate for the swine-flu virus is about 3%.

However, the Center for Disease Control of the United States estimates about 36,000 people in the U.S. died of flu-related causes each year, on average, in the 1990s: see here. Since human beings on the average get the common flu once every one to two years, we can conservatively estimate that a total of 150 million Americans get the common flu per year (based on a population of 300 million). This translates into a fatality rate of only 0.024% for the common flu. This means the swine-flu is potentially over 100 times more deadly than the common flu.

Without access to raw data, I am unable to determine the exact level of statistical significance in the difference in percentages.

However just comparing a potential 3% fatality rate for the swine-flu virus versus a 0.024% fatality rate for the common flu is sufficient to put into serious doubt the merit or even safety of Prof Lee Wei Ling’s suggestion that the population be forcibly exposed, through deliberate neglect, to the swine-flu virus.

Prof Lee may be practicing both bad statistics and horrible science. Health Ministry director of medical services K. Satku has also come out to assert that it is not good practice to expose an individual to a contagious disease to gain immunity as any infectious disease might give rise to complications (see here).

Prof Lee may also not be aware that for common folk and HDB heartlanders, falling ill during a recession like this could mean a loss of income or even the loss of a job. I reject her notion of regarding the population like a herd of cattle that may be willfully exposed to a virus to develop a “herd immunity”.

Only in a population that has succumbed to a herd mentality will such a suggestion be condoned.

Opposition and civil society must come together for sake of democracy Wong gets worse

  1. I actually agree with Lee Wei Ling. I don’t think H1N1 is as bad as its made out to be. The WHO and national authorities were overreacting because of their experience with SARS — for which I don’t blame them. The best way would be to monitor the spread, and make sure anyone who comes down with H1N1 is properly treated.

  2. Your comparison of fatalities : infected and fatalities : total population is also a wrong use of statistic.

  3. “Since human beings on the average get the common flu once every one to two years, we can conservatively estimate that a total of 150 million Americans get the common flu per year (based on a population of 300 million).”

    Sorry, but you don’t get to make up these kinds of numbers. Other quantities are inferred. But to make up a number like loses you all credibility.

  4. I read somewhere (who perhaps), that h1n1 influence A has a mortality rate of 0.4 (4 in 1000), seasonal flu is 0.1 (1 in 1000) .

    but I think
    a) h1n1 might infect 4m ppl in singapore,
    b) yet not everyone catches the seasonal flu…

  5. I disagree with Prof Lee. Think again. The virus harms everyone and especially the weak and vulnerable. By opening the gates, are you prepared for some lost of lives (like in Mexico)? What if that life is your son or daughter, niece or nephew whom you dearly love. The recent death of DBS CEO was probably a result of virus/ bacteria leak in the room where he stayed.

    My son attends childcare since last July. He’s been sick on alternate weeks average ’till this day. That also translates disruptions for the parents. It hurts when i see him suffer like that. We are fighting an unseen enemy.

    It’s inhumane and unethical to let down our guard and allow the H1N1 virus to enter our shores. Not forgetting the panic and the eventual economic cost to Singapore.

  6. Many of us are poor people, not like Lee who is rich, and can get medical attention round the clock.

  7. proof of pudding is in the eating. i suggest Lee Wei ling find her US kakis who has H1N1 virus and get infected, then she can spread to her family. We shall then know whether her theory is correct or not. The question remains, does she only ask people to do as she says, but she doesn’t do as she preached

  8. Hi E-jay, your extrapolating the mortality rate for H1N1 from the Mexican example vis-a-vis the US’ mortality rate for the common flu may not be appropriate. There are many reasons why so many people got infected and died in Mexico – it could be due to the environment, the undeveloped medical infrastructure, genetic predispositions etc.

    I am no doctor but I happen to agree with Lee Wei Ling that developing immunity to the relatively mild H1N1 may be useful in the event that a more virulent strain hits our shores.

    Just my two cents. :)

  9. Dear Josh (comment 3),

    No, I am not comparing fatalities : infected versus fatalities : total population as you suggested.

    I am comparing the same thing in both cases, which is fatalities : infected.

    My assumption is that everyone gets the common flu once in TWO years, which is a reasonable estimate. Assuming a USA population of 300 million, this means 150 million get the flu per year.

    Since 36,000 are estimated by the US CDC to die from flu-related causes per year, this means the ratio of fatalities : infected for common flu is 0.024%.


  10. Gerald

    So you are suggesting that we use 3rd class Sinkaporeans as white mice so that the elite (possibly you) stand to benefit form the result of their tests ntowithstanding a couple of deaths?

    What kind of professor or doctor are you? Doctor Mad?

  11. Dear Anders Brink (Comment 4),

    You say I have lost all credibility by ASSUMING that people get infected by the common flu about once every TWO YEARS.

    Please tell me why this is not a reasonable assumption, and what the correct assumption should be.

    Once every TEN YEARS?

    Every using THAT ridiculous assumption, you have to agree that the common flu is still at least 20 times less deadly than the swine-flu, based on statistics which I TOOK FROM MEDIA ARTICLES AND THE US CDC.

    Mr Brink, from your website you are a science fiction author. Please enlighten me as to how I should, in your esteemed view, correct my assumptions.


  12. Dear Gerald Giam (comment 2),

    I hope you are right, in that H1N1 is relatively benign. Recent experience seems to indicate thus, but in my view it is way too soon to tell.

    Unlike the common flu and contagious diseases like chicken pox which is very well established medically, H1N1 is a relative unknown. We need much more data to decisively say that H1N1 is definitely benign.



  13. E-Jay:

    1) I think you are conflating influenza with the common cold, which is much milder than the flu (http://www.cdc.gov/flu/about/qa/coldflu.htm). Medical practitioners here in the U.S. always stress that there is a difference between these two, which I think is not made clear in your post.

    2) Each year, about 5-20% of US population get the flu, but only ~200k get hospitalized for serious symptoms (http://www.cdc.gov/flu/about/qa/hospital.htm). Perhaps there is a tiny chance that 150 million folks here may be infected with “common flu,” but the available CDC data don’t support your assumption.

    3) For the 2,000-odd swine flu/H1N1 hospital cases that have been reported in Mexico, I’m very, very certain that there is a vast number of “infected” that did not report to the hospital. Maybe these folks don’t want to go to hospital as bed rest is sufficient. Maybe the Mexicans are under-reporting the actual number – it would not be the first time it’s happened. For all we know it could be up to 10, 20 or 50 times more than the the 2,000 cases you report. And, given the current U.S. data – see point 4 below – I’m almost certain that this is the case.

    Fact is, I would be very, very hesitant to claim a 3% fatality rate (potential or not) without knowing the data quality. Funny thing is, you do add that proviso and yet base this post on this conclusion. There’s some irony there…*shrug*

    4) Here’s some actual data from the U.S> CDC (http://www.cdc.gov/h1n1flu/)

    As of 15/5/09, there are 4714 confirmed or probable cases of H1N1 flu and 4 deaths in the United States. Do the math.

    5) Don’t you think you are just as guilty as LWL of bad stats and science? Just saying. :)

  14. Hi Winston (comment 15),

    Thanks for your updated data/hyperlinks and comments.

    The statistics are certainly very conflicting right now. No firm conclusion can be drawn.

    However, I stand by my view that Prof Lee Wei Ling’s suggestion is a bad one. How can you regard the population as a herd of cattle to be willfully exposed as you please? People’s lives and jobs are at stake here!

    The country should not be turned into a petri dish!



  15. Dear Sir/Madam, I noticed that you were leveraging heavily on the statistical comparision between Mexico and the USA.

    Just a friendly reminder: unbiased representative inferences can only be made by comparing random samples i.e. must have similar background la!

    Surely we can’t compare the flu mortality rates of… let’s say Indonesia and Singapore right? =/

    Your recession point was generally valid, but perhaps it would be wiser to review/retract the statistics argument which you completely bombed, to put it rather crudely…

  16. Look here. Your estimate is not even in the ballpark. Why is it reasonable to assume EVERYONE gets flu on average of once per two years?

    Since I’ve never gotten the flu since age 15, is it reasonable to assume that the average figure is once every 20 years? Of course not!

    _Collect_ the data from peer reviewed papers! Don’t guess. It is not acceptable to guess when there is better data. You need this better data to argue against Prof Lee.

  17. excellent rebuttals by the readers, especially acidflask who has taken the trouble to refute ng e-jay point by point.

    ng, you should be heartened by the intellect displayed by your readers. Shows that you are attracting the right crowd.

  18. I actually agree with Dr Lee. H1N1 is not all that bad. It depends on how one looks at it at a different prespective

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