Thursday, April 30, 2009

Swine Flu

Over-hyped? Justifyingly frightened? What should we make of it?

So far just a handful of cases apart from in Mexico, where the death rate is about 7% of those known to have been infected. Outside Mexico the illness has been pretty mild.

Influenza A is an unpleasant illness causing fever, headache, sweats, debility, backache, and features of a head cold. In the worst cases pneumonia develops and this can be either viral or a secondary bacterial. Deaths are pretty rare but they do occur. Historically, everyone fears another 'Spanish Flu' which killed many millions after the first world war.

Every year the common type of flu changes slightly so that a new vaccine is produced to give protection to the most vulnerable. Every dozen years there is a major change which results in a type of flu spreading around the world. I have had Asian flu in 1957, Hong Kong flu in 1968, and Russian flu in 1979. I spent 4 days in bed on each occasion and was so ill that there was no confusing it with a cold. For the past 30 years I have never had flu.

It appears that the new strain coming out of Mexico is so different from what went before that most people have no immunity, and therefore it will spread rapidly throughout the world. What seems strange so far is that it seems very virulent in Mexico and quite mild outside that country. However, we don't have enough information yet to make a judgement on how dangerous it is going to be.

It should be assumed that many people exposed to flu will suffer no symptoms, so the number infected in Mexico may be many more than the number tested positive. The deaths will be the same so the death rate is probably much less than 7%. The fact that only mild cases have been seen outside Mexico tells us nothing yet. If, say, only <1% of cases are fatal, we would have to have many more cases before our first death. Since all contacts are being tested we will get a poor picture of what is really going on. Many of these cases will be subclinical so the true incidence of flu will be difficult to estimate.

There is some evidence that it is the immune response that is lethal, so those with poor immune systems may be better off, but I would not want to rely on this.

What can one do? Obviously, avoiding crowded places, not traveling and avoiding anyone with an infection is wise advice, but I would not regard this as essential at the present. Wearing a mask works for about 30 minutes, but after that the mask becomes soggier enough to fail to protect. Most infection is cause by hand to hand contact so avoiding shaking hands is good advice. Wearing a mask may prevent you transferring flu from hand to face, but it should anyway be a discipline for people with poor immunity. The new strain seems susceptible to Tamiflu, so you should get hold of a supply if you think you have been exposed. there is plenty available to cover those who really are infected, but don't panic buy.


Anonymous said...

Most of the pictures coming out of Mexico show, what appears to be, surgical masks which are not tight fitting. In the US, N95 masks are tight fitting and are available with or without exhaust valves. The valves help keep the interior of the mask cool and help prevent the sogginess you mentioned.

Deb Light said...

Thanks for your take on the "Swine Flu" Dr. Terry.No need to panic yet.Let's pray it doesn't get out of hand.

God Bless,

Anonymous said...

Dr Terry,
Would you have any additional advice for a person diagnosed with SMZL and splenectomized, who works as a front line health care provider in home care?

Terry Hamblin said...

This comment comes a lot later than the article. There are now 29 deaths in the UK; almost all of them in people with underlying health problems. For most people the disease is mild and it seems likely that if you had the 1957 Asian flu you might not be at risk. The advice I gave in the article still holds, but I have been avoiding crowded places and particularly avoiding grandchildren since I am in one of the at risk categories. I would advice those who have compromised immune systems to do the same.

Pregnacy is a bit risky, and 2 of our 29 deaths were pregnant women. They can't have Tamiflu and the other anti-viral choice may be less effective. There is some discussion here on what advice to give. I would say that the only extra advice I would give is stay away from nurseries if possible. Even so most cases in pregnancy are mild.
Put the risk in perspective: the death rate is less than one in a thousand - perhaps 50,000 people have had H1N1 in the UK. It is more dangerous to ride a motor bike.