Swine Flu Anxiety

While in the midst of an epidemic, a great deal of anxiety arises in the population.

Anxiety can lead to an exaggerated or inaccurate perception of risk, particularly when the mass anxiety is spread in the media, such as via front-page accounts of unexpected deaths.

In approaching any type of anxiety, I think it is important to know exactly what the risks are.

So, for example, it would be dishonest to tell an airplane-phobic person that air travel is perfectly safe. It isn't: there is about a 1 in 1 million chance of the plane crashing. (In a future post, I'd like to present my analysis of the statistics, and also show that the average spontaneous death rate in the population, for a person beyond young adulthood, exceeds the death rate from flying in an airplane--therefore I could claim--flippantly--that flying is statistically a "life-prolonging activity" for most travelers).


The current flu epidemic is clearly a serious matter. There definitely is a risk of death for those infected.

Estimates I've seen of the mortality rate vary, but the prevailing opinion seems to be that it is less than 0.1% (1 in 1000) for those infected.

This is not particularly different from the mortality rate of ordinary seasonal flu.

HOWEVER, the significant difference in this epidemic is the mortality rate by age. It is clearly true that swine flu has a higher mortality rate for healthy young adults--probably at least triple-- compared to seasonal flu.

Therefore, we are seeing more young, healthy adults die of flu this year. The total numbers are very low, but are much higher than in other years. The reason the overall mortality rate is the same is that fewer elderly individuals are dying of swine flu, most likely because of heightened immunity in that population due to exposure to a similar virus decades ago.

The CDC site shows that in a cohort of 268 people who died from swine flu early in the epidemic, 39% were in the 25-49 age group, and 25% were in the 50-64 age group. This is very different from seasonal influenza, in which about 90% of the deaths are in the over 65 age group. Here's a link to a pertinent page from their site:
http://www.cdc.gov/H1N1FLU/surveillanceqa.htm

Here's another important page from the CDC:
http://www.cdc.gov/h1n1flu/estimates_2009_h1n1.htm

Based on the table shown on this page, here are estimated risks of death for individuals infected with H1N1, stratified by age:
0-17 age group: between 1 in 10 000 and 1 in 20 000.
18-64 age group: between 1 in 2400 and 1 in 6000.
65+ age group: between 1 in 2300 and 1 in 6800.

I found a table of age-standardized "excess deaths" due to pneumonia and influenza in Italy between 1969-2001. (http://www.cdc.gov/eid/content/13/5/694-T2.htm) Based on this table, and assuming that only 10% of the population is infected during typical seasonal flu years, here is a very rough estimate of the risks of death by age for seasonal flu:
0-44 age group: 1 in 100 000
45-64 age group: 1 in 20 000
65+ age group: 1 in 750

The above data show that H1N1 influenza has a substantially higher death rate for those under 65 compared to seasonal flu, but as you can see the chances of dying if you catch the flu are still quite low, regardless of your age.


The risk of flu vaccines appears to be extremely low.
There is a substantial risk of contracting flu without the vaccine.
There is a low but non-zero risk of severe illness or death if you contract the flu.
The risk of a severe adverse reaction to the vaccine is much lower than the risk of a severe adverse effect from the flu itself.
The vaccine is likely to reduce the risk of contracting the flu by at least 90%.
Therefore, the benefit:risk ratio regarding the flu vaccine is very favourable. Here are references:
http://www.cdc.gov/h1n1flu/vaccination/safety_planning.htm
http://www.who.int/csr/disease/swineflu/frequently_asked_questions/vaccine_preparedness/safety_approval/en/index.html

So, my recommendations regarding swine flu anxiety are to be informed about the most accurate facts available:

1) the risk of death or severe illness remains low, for anyone infected

2) but the risk of a healthy young adult becoming severely ill or dying is relatively higher compared to seasonal flu

3) public health measures, such as very careful hygiene and mass vaccinations, are likely to save many lives (this is true of seasonal flu as well). Statistically, you as an individual are unlikely to contract severe flu illness. Hygiene and vaccine recommendations are more likely to be part of reducing the spread of flu in the population: therefore such recommendations, if you follow them, are statistically more likely to spare severe disease in someone else, rather than yourself. That is, if you receive a vaccination, that vaccination is more likely to save someone else's life rather than your own, since the average active case of flu is likely to spread to about 2 other people, even if the case is mild.

4) Therefore, I encourage following hygiene protocols and receiving the vaccine when it becomes available. It may spare you severe illness, and it has an even higher likelihood of being an altruistic act, which spares other people severe illness. Prompt use of anti-influenza medications such as Tamiflu are likely to further reduce the risk of severe complications, and most likely will further reduce the risk of contagion.


Altruistic acts, such as getting vaccinated or washing your hands, are psychologically healthy (this is my justification for posting something about influenza in a psychiatry blog!).


*It may be important to keep in mind, for the sake of perspective, that automobile accidents, for example, claim about 600 000 lives per year among young, healthy adults. In Canada alone, there are about 1000 deaths of young, healthy adults per year due to car accidents. (reference:http://www.statcan.gc.ca/pub/82-003-x/2008003/article/10648-eng.pdf) Another altruistic act of very practical importance is to slow down on the road!

Addendum:
A good article in the November 10, 2009 edition of CMAJ (p. 667-668) presents evidence that handwashing is not actually likely to be very effective in reducing the spread of influenza. Microbiologist Dr. Donald Low argues that hand hygiene has not been proven to reduce influenza spread, and that the influenza virus is primarily spread by fine droplets from coughing, which then have to be inhaled deeply. He points out that receptors for the influenza virus are located farther back in the respiratory tract, hence cannot be easily infected by touching mouth or eyes with hands, etc.
Here is an excellent article on the subject:
http://www.scienceadvice.ca/documents/%282007-12-19%29_Influenza_PPRE_Final_Report.pdf

His evidence-based position is that the N95 mask is the best mechanical way to prevent infection if you are near an infected person. Other than that, the best practice to prevent contagion would be to contain any coughing or sneezing, to stay away from other people if you are coughing, and to avoid close proximity with those who are infected, if possible.

Meanwhile, it is undoubtedly true that good handwashing practices do reduce the spread of the common cold and other infectious diseases. So all the handwashing and hand-sanitizing stations you see all over the place remain a good idea -- it's just that handwashing might not actually protect you very much from contracting influenza, compared to other measures.