Deadly Companions by Dorothy H Crawford

I've just finished reading Deadly Companions by Dorothy H. Crawford - a book I have been hankering after for some time (after reading this author's The Invisible Enemy (about viruses) which was also fascinating).

One thing I love about books like these is that they are packed with little nuggets of information. Here are a few that I've learnt:

Chloroplasts and mitochondria are the result of cyanobacteria (which had developed the ability to convert sunlight into energy) and alphaproteobacteria (which had developed the ability to use the side-product oxygen yielded from all this photosynthesis) being incorporated into the cells of other bacteria.

Many bacteria contain plasmids which can be transferred during something called conjugation when a filament called a sex philus passes the plasmid from one bacteria to another. These can contain information favourable to the survival of the bacteria.

Viruses that attack bacteria are called phages and these sometime set up long-term symbiotic relationships with the bacteria. These are responsible for the toxins in diphtheria and cholera bacterial infections.

We each house 10 to the 14 microbes weighing 1kg and these outnumber our body cells 10 to 1. Some of them help us digest food and aid immunity or help kill off other more virulent microbes. They become harmful when they go where they shouldn't e.g. during surgery.

During the AIDS epidemic among gay men in the 1980s there was a super-spreader, who was thought to be an airline steward who spread the virus around the cities of the world with 40 sexual contacts per city.

During each epidemic there are silent infections - people who exhibit no symptoms but are infectious. The proportion varies.

All diseases become less virulent over time.

Chicken pox, herpes, cold sores, shingles are all related and are probably ancient inherited from ape-like ancestors. They rarely kill but spend most of the life-time of the host well buried and away from the immune system only coming out occasionally causing pustules and sores filled with viruses. If they didn't behave like this they would have annihilated the small hunter-gatherer groups where they originated.

Those are just a few facts, and there are lots, lots more. Dorothy H. Crawford outlines the history of mankind, taking in all the common infectious diseases - their action and effect on the body, where they are though to have come from and then, most interestingly, the effect these outbreaks had on human history. She spends one chapter on Ireland and the diseases that occurred in the wake of the potato famine, before going on to look at more recent emerging diseases and what might happen in the future.

The book is very well-written and utterly absorbing and I recommend. (And if you're wondering about the outfit on the cover it is the outfit used by physicians to ward off the plague as they did their rounds. The beak was supposed to hold aromatic herbs... It didn't work.)