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.