Swine Flu

Reading this blog reminded me that I wanted to look into the real risk of swine flu. What are the chances of catching it? What are the chances of dying from it? Is this all a storm in a teacup?

Typing "swine flu mortality" into Google yields this article (as the first page, no less) that nicely explains the concepts of virulence, case fatality ratio (CFR) and mortality. I'm not a medical expert in any respect, but it does pass my "common sense test", so I will summarise it (although I really recommend that reading it for yourself if you are interested):

• virulence is severity of the disease the virus produces (note that this is related not only to the virus, but also the host. I'm only going to be talking about humans)


• CFR is a measure of virulence - it is the probability of someone who has caught swine flu dying from it


• mortality rate is the percentage of the population that die from swine flu


• it is very difficult to put accurate numbers to these rates

However I have noticed that many places are using mortality rate interchangeably with CFR, but I will try to stick to the definitions above.


World Health Organisation (WHO) figures (via the UK government) as of the 26th June are 59,814 cases worldwide and 263 deaths. This gives a CFR of just over 0.4%. For comparison Wikipedia gives the following figures:

1918 flu pandemic >2.5%
Asian flu <0.1%
Hong Kong flu <0.1%
Seasonal flu <0.05%

So, it looks like swine flu is more deadly than normal seasonal flu, but not nearly as deadly as the 1918 pandemic, once you've caught it. But how easy is it to catch it?

The WHO has declared swine flu to be a phase 6 pandemic, meaning that there is widespread human infection. Their assessment of the pandemic includes:

"H1N1 appears to be more contagious than seasonal influenza. The secondary attack rate of seasonal influenza ranges from 5% to 15%. Current estimates of the secondary attack rate of H1N1 range from 22% to 33%."

So swine flu is easier to catch than normal flu, as well as being more virulent. However is is worth noting that the World Health Organisation FAQ about swine flu "what is level 6?" says that the pandemic is moderate.

The moderate assessment reflects that:

* Most people recover from infection without the need for hospitalization or medical care.
* Overall, national levels of severe illness from influenza A(H1N1) appear similar to levels seen during local seasonal influenza periods, although high levels of disease have occurred in some local areas and institutions.
* Overall, hospitals and health care systems in most countries have been able to cope with the numbers of people seeking care, although some facilities and systems have been stressed in some localities.

Based on the above, I conclude that swine flu is indeed worse than seasonal flu, but not the end of life as we know it that some people fear. Luckily, the recommended precautions are not too onerous:

* cover your mouth and nose when coughing and sneezing, using a tissue
* throw the tissue away quickly and carefully
* wash your hands regularly with soap and water
* clean hard surfaces (like door handles and remote controls) frequently with a normal cleaning product