E. coli outbreak – what do we know so far?June 3, 2011
In the last week there has been international news coverage of an outbreak of E. coli that has been going on in Germany since the beginning of May.
I wanted to very briefly cover what is causing this outbreak and what is known about it.
Escherichia coli is a species of bacteria that is found across the world. There are many strains, some of which live in our guts completely harmlessly. Others like E. coli O157 live in the guts of animals and can cause disease in us if we encounter them. The symptoms infected people show depend on the strain but can include bloody diarrhoea and Haemolytic Uraemic Syndrome (also known as HUS) which happens when the kidneys are damaged and it is children who are most commonly at risk.
The outbreak strain in Germany is unusual. It is serotype O104:H4 - and is a variant that has not been seen in an outbreak before. (It is currently being called a variety of things in the press. STEC= shiga toxin-producing E. coli. VTEC= verocytotoxin-producing E. coli. And when EHEC = enterohaemorrhagic E. coli is used it is referring to the bugs causing bloody diarrhoea.)
It is also unusual in that the majority of the people affected are women over the age of 20. Many of the cases show bloody diarrhoea but a larger proportion than expected are resulting in HUS. There have been 13 deaths and the cases number in the thousands. Although there have been cases reported in many other countries, all of the cases except one have so far had a recent travel history of visiting northern Germany. The one case had been in contact with someone who had recently been in northern Germany.
It is being reported that this E. coli strain is producing extended spectrum beta-lactamases which increase its resistance to certain types of antibiotics and it appears to be carrying genetic material from several different strains of E.coli which is making it more virulent and increasing/altering its toxin production (although I haven’t been able to find much information on this yet – if you know of anything I’d love to hear about it in the comments).
It currently looks like the source of the contamination may be consumption/preparation of raw salad vegetables – tomatoes, cucumbers and lettuces have come under suspicion – but how they got contaminated is currently unknown.
It is also not known why it seems to be affecting adult women much more than any group. There are speculations that it may be to do with food preparation habits or eating habits or it may be something more biological, for example hormone production. However, nothing has been confirmed yet so we will just have to keep watching.
In the meantime the HPA in the UK are advising anyone travelling to Germany to avoid eating raw salad vegetables (see the link below).
This post has been a very very quick run-through of the situation – below are more links for anyone who wants to know. I particularly recommend the Nature News and the der Spiegel articles – both are easy to read and very informative.
I will try to keep track of further news as it happens and will be tweeting it over the weekend and hopefully add another update here next week if substantially more is known. In the meantime – if any of you have seen any other links please do share them in the comments.
Excellent coverage of the story:
Is it novel? by Mike the Mad Biologist
More on the novelty (or not) of it at Aetiology
Outbreak surveillance links: