2005-11-01

Strategy to fight virus (H5N1 avian / bird flu): buy time to immunize our population

Sun Zi said,

  • "It is the rule in war, if our forces are ten to the enemy's one, to surround him; if five to one, to attack him; if twice as numerous, to divide our army into two.
  • If equally matched, we can offer battle; if slightly inferior in numbers, we can avoid the enemy; if quite unequal in every way, we can flee from him.
  • Hence, though an obstinate fight may be made by a small force, in the end it must be captured by the larger force" - Sun Zi Chapter 3 Attack by strategem
  • "故用兵之法,十则围之,五则攻之,倍则分之,敌则能战之,少则能逃之,不若则能避之。故小敌之坚,大敌之擒也。" - 孙子兵法.谋攻.三
Lesson in military strategy: If you have 100 soldiers, and you send 1 out each time to take over a castle guarded by 10 soldiers, you will fail.

Lesson in marketing strategy: If you have 1M in marketing budget, and you spend 10k each day on different street or buy one ad spot each at random time, you cannot build a brand. You need to concentrate the exposure in a short period of time focusing on your target customers.

Such insights can be applied to our fighting against bird flu, and contagious diseases in general.

A) The debate on treating the birds


There has been a blame (via TPD) and defense game about who is responsible for the strains of virus which developed resistance to the anti-viral drug amantadine in SE Asia.

  • Some researcher in US speculated that the application of amantadine in chicken farms in China led to the development of drug resistance
    • "Experts there reported last month that bird flu strains in East Asia, particularly in China, had become more resistant to amantadine during recent years. They also said the mutations in China did not appear to be random, adding they could be the result of treating chickens with the drug to prevent bird flu." -Washington Post
  • Jia Youling of China's Agriculture Ministry said it is unfair to blame China for the resistance of the virus strains. (fig=vaccine shot in china; note amantadine is given orally, mixed in its food, and daily)
    • 'The Chinese government has denied that it urged farmers to use amantadine to suppress bird flu outbreaks. But Jia said some Chinese poultry farmers have used the drug in the past on the advice of the Merck Veterinary Manual, a leading guide for the veterinary profession around the world. The manual's online edition lists amantadine under the prevention and treatment section of its entry on influenza. It says the drug "reduces the severity of influenza in some avian species, but amantadine-resistant virus frequently emerges." '
    • "Jia said "only very limited samples" of the bird flu virus tested in China last year and none of the samples tested this year had mutated and become resistant to amantadine. By contrast, he said, the vast majority of bird flu virus samples tested in Southeast Asia had become resistant." -WaPo
    • He also said the economical cost of using amantadine is more expensive than that of vaccine in China, because vaccine is cheap and one shot is good for 6 months.

Personally I think the blame game is childish and does not help our war on H5N1. The blame/avoid-blame mentality had served to amplify the crisis of SARS in 2003, when some international media blamed China for the new virus species and the idiot Zhang Wenkang spent more time drawing the 'analogy' of US and Africa as the source of AIDS (HIV) than telling the Chinese people of the truth.

Suppressing truth is a crime (as in SARS) as it reduces our vigilance and helps the virus to spread. However, suppressing the outbreak in farm fowls may not be. In fact, buying time by suppressing and delaying the outbreak is perhaps one of our best defense against virus. Let me explain this below.

B) Technical Backgrounds

Before going into the strategy to fight a virus, some background knowledge on virus and on H5N1

  • Virus is as different from bacteria as plant vs animal. Virus is basically a set of nucleic acid, RNA or DNA, but not both. Virus does not even have cell membrane. All other organisms (bacteria, plant, animal) have cell membrane and both types of nucleic acids.
  • H5N1 is a newly discovered (1997) strain of bird flu. Other flu virus are classified as HaNb, where a/b are numbers. Most of the flu outbreaks in human history are believed to be related to (or started from) birds.
  • Human beings have had great success against bacteria infection (e.g., cholera, TB) since the discovery of penicillin. But we still do not know how to treat virus effectively. That is why SARS, AIDS are so difficult to treat
    • There are not many anti-viral drugs at our disposal today, so far we only have 3 plausible drugs to treat flu, Roche's Tamiflu (aka oseltamivir), and its relative Relenza, aka zanamivir); and the older drug amantadine and its relative.
    • Most people (and bird) heal from virus infection (including flu) without medical treatment, due to our own immunological response (our body can produce antibodies that target the specific invader ourselves). A strong body, less stress, lot of rest helps. The reason I said drugs like Tamiflu are not very effective is because there are perhaps as many (or more) people who heal without using Tamiflu than those who used. (But even if the effecacy is 20%, it is still worth trying. That is why many hospitals are using it)
  • Abuse in anti-biotic leads to resistance in bacteria. But it does not affect the treatment of virus..
    • Just like insecticide resistance does not change the effect of herbicide
    • However, abuse of anti-viral will affect the efficacy of that specifc antiviral drug or even other drugs in the same family
  • One important fact is that once we are able to generate antibody to a specific strain of virus ourselves, we are immune for live. If we surived H5N1 or survived a SARS infection, we would never be infected by the same strain of virsu again. Then why do we catch flu more than once? because each time it is a new strain of virus. Each year the flu vaccine is different from that in the previous year.

C) Strategy to fight the virus

Understanding the last point above is important in our discussions below. There are 2 obvious strategies to fight H5N1.

  1. Build a physical line of defense, fight back each infection, quarantine patients, kill every bird
  2. Suppress major outbreak, quarantine patients, buy time and hope for more people would become immune in the meantime (I will elaborate on this later).

Option 1 is basically what we have done when we fought SARS. If SARS is, as alleged, passed from civet cats, which are very shy animals, once we have eradicated the virus in our environment and promise not to pat (or catch) civet cats again, we are pretty safe.

However, option 1 does not work for bird flu. Because, as you can see in the chart on the right, our fowls may contact with migrating birds, and migrating birds fly all over the earth. They are a lot more mobile than civet cats. There is no way we can cut our contact with these birds, nor should/could we kill all these birds.

So we are actually left with option 2, and minimize human death. Considering the fact that it had been a full 8 years since we first saw H5N1 in 1997, we have been extremely successful. We have bought a lot of time and many people in SE Asia and South China may already be immune to this virus. This is because, for every human infection of H5N1, there must have been thousands who might have contact with the virus and end up healthy, because the amount of virus is small or the human being is strong and able to generate antibody to fight the virus.

In fact, many of us may already be immune to H5N1 (and even SARS) at this moment. When more and more of us become immune, it will be very difficult for virus to spread between human beings (so far all cases observed have been bird to human), because when the virus jumps to the next person, he might already be immune and the chain of infection will stop there. (Analogy: firebreak in the forest) Some suspect this mechansim is also responsible for our winning the war against SARS (many in South China might already be SARS immune).

  • Contact with a weak virus, while you are healthy and strong, is how Dr Jenner discovered the vaccination against small pox. The girl pictured at the top of this post is probably immune from H5N1. (However, do not go out to kiss birds now, since you are not sure if you are strong enough, or if the virus in not lethal)
  • In other words, buying time is effectively the creation of a natural process to immunize our population, and equip ourselves in am arms race against the virus. The analogy of a 10 soldier guard against a 100 soldier attacker applies, except that after each battle the winner gets stronger.

Therefore, buying time is very important in our war against virus. Effective suppression and treatment of chicken is one of the measure we can adopt to buy time. In fact, instead of killing birds en masse (HK in 1997), we may want to simply isolate these chicken and see how many of them survive the pandemic. It is certainly a more human way to treat these animals, and it is also scientifically justified.

D) Implications to ourselves

  • No need to panic, but be vigilant
  • Avoid contact with birds, contact with human are still safe so far (until a mutated strain appears, it has not for the past 8 years)
  • Exercise to maintain fitness, avoid stress, sleep well and rest well
  • The buy-time strategy also works at individual level: If you caught a cold or flu, the first day is extremely importantly. If you can cope with it well, you got youself enough time for your own immune system to figure out the weakness of the virus and develop weapon (antibody) agaisnt them, before they could multiply exponentially.

p.s. After reading the backgroun material above, you would know why Roche's allegation that Taiwan's applying its own version of Tamiflu will generate resistant virus strain is full of bullshit. Because, resistance is only generated when the treatment fails and the virus survive and pass on its genes. If Taiwanese doctors are following the proper procedures, the risk (of resistance) will be no different from those in Europe or US.

5 comments:

Yuentze said...

Just one question. I guess virus can survive on the gal's lips. Possible?

Sun Bin said...

yes, if she survives after a few days. she is immuned and safe.

Yuentze said...

Then she will pass on the virus if she kisses others?

Sun Bin said...

There is so far no evidence of H5N1 transmission between human being (only one suspected case in the past 8 years, and it was inconclusive).

So, you can kiss that girl no problem.

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