Archive for the ‘Essay’ Category

Multiple Sclerosis: blaming the sunshine

March 31, 2011

Multiple sclerosis (MS) is an unpleasant neurological disease, displaying an unpredictable range of symptoms which manifest themselves with equally unpredictable severity and rapidity. It is an autoimmune condition affecting the nerves: during relapses, an over-enthusiastic immune system attacks and damages the protective coating of nerve cells in the brain and spinal cord. People are often diagnosed in their most productive years— their 20s, 30s and 40s— when they must learn to deal with an uncertain prognosis, often ending with debilitating loss of mobility, speech, and memory at an unforeseeable point in the future.

For many years, the cause of the disease remained a mystery. Then, in 1960, Donald Acheson proposed a link between sun exposure in early life and a later diagnosis of MS. This hypothesis was founded on a growing body of evidence suggesting a north-south gradient of diminishing disease risk, based on research in several different northern hemisphere nations. Early studies demonstrated this relationship in World War 1 veterans living in several US states, and across populations in different regions of Norway. In the next few years similar associations were found in the southern hemisphere, but this time going in a reverse direction— with a higher risk of disease in the south versus the north— and it was discovered that immigrants tended to bring the risk of their original country with them when they moved, suggesting exposure in early life was an important factor. It seemed like Acheson was on to something.

Meningitis in Africa

February 21, 2010

In the developed world, meningococcal meningitis is mostly a ‘sporadic’ disease. About 10% of us carry Neisseria meningitis as resident bacteria at the back of our throats. If we’re very unlucky, a few cells may find their way into the blood and circulate to the membranes lining the brain- the meninges– and establish a breeding population.

When this happens, it’s bad news.

Although readily treatable with antibiotics, mortality rates from meningococcal meningitis are relatively high, even in western countries. Thankfully it’s rare. Occasionally, short-lived outbreaks of the disease occur in situations where groups of people live in close proximity and share respiratory or throat secretions (intentionally or otherwise). These infrequent disease clusters typically occur in schools or universities, but don’t usually affect more than a handful of people at a time.

In some parts of the world, however, meningoccal meningitis behaves very differently. The worst affected of these regions is the so-called meningitis belt of sub Saharan Africa, where the disease can occur in devastating seasonal waves which sweep through the population. The worst ever epidemic— in 1996— killed around 25,000 people. The 2009 season was a bad one, too; despite vigorous control efforts there were over 1500 deaths.

Why does the disease occur in epidemics in Africa, but not in Europe or North America— and why are these epidemics seasonal? And what can we do about it? These are interesting questions if you have interests in both health and the Earth sciences. If you haven’t, stop reading now.

The public health implications of T Pyxidis

January 25, 2010

No, not an unusual pathogen, but a supernova.

This is a belated response to the news that a white dwarf in a binary star system named T Pyxidis is approaching its Chandrasekhar Limit- in other words, it’s close to going ka-boom- and, according to a paper presented at this year’s American Astronomical Society meeting, at 1000 parsecs, it’s closer to us than originally thought.

If we assume that the supernova of a nearby star of would “destroy all life on Earth”, this makes for an attention-grabbing story. Cue headlines like this. The end of the world angle gets talked up, before we get the reassuring news that this is unlikely to happen for 10 million years or so.

Could this really be true? Leaving the unpredictable behaviour and location of T Pyxidis to one side, I spent a few minutes link-and-google sleuthing to try to get to the bottom of the supernova-destroying-life-on-Earth bit. Writing it up will no doubt take longer. My rigorously scientific search strategy led me to the following conclusion: while it’s all very uncertain and (of course) low probability, high impact stuff, it’s perhaps a little more interesting than the headlines suggest.

Resilience and Haiti

January 17, 2010

A couple of weeks ago I was introduced to a new concept: resilience.

Actually, it’s an idea that’s been around since 1973, albeit one that’s grown in prominence in recent (post 9/11?) years. But this was the first time resilience has crossed my radar in anything other than its common-or-garden dictionary definition sense.

The dictionary (Oxford Reference) definition of ‘resilient’, by the way, is ‘springing back to its original form after compression’.

The Lusi Mud Volcano

January 3, 2010

Lusi mud flow, November 2008

The story of the Lusi mud volcano in Indonesia is a fascinating mix of geology, health and human intrigue.