By Dr Wong Wee Nam
17 May 2009
When the news of the outbreak of H1N1 virus in Mexico broke last month, the health authorities and the governments of the world went into frenzy. Governments started to stockpile anti-flu tablets and protective gears.
People panicked. It did not help when the WHO asserted that a “global outbreak of the disease (was) imminent.”
Of course, the media also got into the act of fanning the fear and anxiety. The claim that more than a hundred people had been killed in Mexico raised the fear level even higher though only less than ten of these deaths had been corroborated by laboratory tests to have been caused by the H1N1 virus.
Photographs of pigs in cages and television pictures of healthcare workers in masks, caps, gowns, goggles and gloves all helped to enhance the spectre of impending doom.
With headlines and terms like:
- “The worst health crisis facing the world in 90 years…”
- “total number infected might run into tens or hundreds of thousands.”
- “the “inevitable spread” of the disease”, etc,
it is no wonder that the atmosphere of fear and insecurity generated has made us forgotten that there is an economic crisis that had yet to be solved and that many more people are still dying everyday from poverty, neglect and hunger. Most press reports lack rational scientific analyses.
Like the rest of the world, Singaporeans are not spared from this panic. Thus when Professor Lee Wei Ling wrote a letter to the forum page in the Straits Times published on May 13th 2009 under the heading “Let it in while benign to develop herd immunity”, she created a lot of anger amongst her readers.
What she said was:
1. It is impossible to prevent the virus from entering Singapore by just screening those entering here who are ill and/or febrile.
On this point, she is right. In all infectious diseases, most carriers of a virus are healthy people. It is in the interest of survival of a virus to do so. If only sick people carry viruses, then the spread will die a natural death. Therefore, even with all this screening, the virus will still make its way into Singapore. Temperature screening is a futile exercise.
2. Though the H1N1 virus is contagious, it has low morbidity and mortality.
So far statistics and clinical progression of the disease have supported this point. Many scientists now feel that this flu is not fatal as the strains that caused some previous pandemics. It may “not even do as much damage as the run-of-the-mill flu outbreaks that occur each year”.
3. Her third point is that we should allow this relatively benign H1N1 virus to come into Singapore so that our people can develop herd immunity from it.
On this third point, members of the lay public felt aghast by the suggestion. Even the Ministry of Health also thought that it was a bad idea. Health Ministry director of medical services K. Satku said, “Generally, as a principle, it is not a good practice to expose an individual to a contagious disease to gain immunity as any infectious disease might give rise to complications.” (Straits Times 15th May)
However, I agree with what Professor Lee had suggested and don’t understand the principle that Prof Satku is talking about. Short of living in a sterile protective bubble, we are all exposed to contagious diseases every day and gain immunity from them. Our body at any one time is playing host to more that a thousand different types of microbes. In total it is estimated that there are between 10 trillion to 100 trillion of these creatures in our body.
Exposure to contagious diseases to gain immunity occurs all the time. Any parent will discover that when the child starts pre-school or kindergarten, he or she gets exposed to contagious diseases and gets sick easily. However by the time the child goes to Primary 3, he or she is seldom sick. This is because the child has, by that time, acquired the natural immunity to many diseases.
The same goes for a primary health care doctor who is assaulted everyday by all kinds of microbial creatures.
To me, creating a herd immunity is a sensible immunological principle. It is a fact that when the immunity possessed by the general population as a group is low, an infectious disease is likely to spread rapidly and is often of a more severe form. When herd immunity is high, the disease is more likely to spread slowly and to be clinically mild. Thus herd immunity is a good thing in preventive medicine.
The Health Minister, Mr Khaw Boon Wan, in the same report (Straits Times 15th May) said, “I suppose at the individual level, you can experiment with your lives. But I think as Health Minister, I cannot experiment with Singaporeans’ lives, particularly when there remains incomplete information about the virus.”
This being so, I think the Minister should therefore give some thought to the principle of herd immunity rather than dismiss it. We can learn a lesson from the Fiji measles epidemic. Prior to 1875, no epidemic had known to occur in Fiji Islands. As a result, as a population group, it had no herd immunity. In 1875, a visiting ship introduced the measles virus to the Islands. This resulted in a severe epidemic which killed 25% of the population.
Sometimes being too sterile can do more harm than good.