Frequently asked questions on the EHEC infection outbreak in Germany
Epidemiology
06-06-2011
1. What is the source of contamination?
The source of the infection has not yet been identified and intense investigation is being carried out to find it. Contaminated bean sprouts, lettuce, tomatoes and/or cucumbers are the most probable vehicle of infection, but this is still not proven. Escherichia coli outbreaks are usually foodborne. Other food items or materials may be culpable.
2. Why are the investigations taking so long?
This is a complex effort as the bacteria can be transmitted in so many ways – through water, food or contaminated material. Investigating the particular source involves many different agencies, complex laboratory tests, research and tracing, and requires isolating the bacteria and investigating patients’ exposure in detail.
3. How are the bacteria transmitted to humans?
The bacteria are transmitted through the faecal/oral route and eating contaminated food is a common vehicle of infection, often through contaminated raw or undercooked ground meat products, raw milk and fresh produce. Other sources of enterohaemorrhagic E. coli (EHEC) infection are contaminated water, and contact with animals and with other affected patients, if proper infection control is not practised.
4. How long is the incubation period of EHEC infection?
The incubation period is usually about 48 to 72 hours, but can range from 1–10 days.
5. What are the symptoms of EHEC infection?
Symptoms of disease include abdominal cramps and diarrhoea, which may be bloody. Fever and vomiting may also occur. Most patients recover within 10 days; in a few cases, however (particularly in young children and elderly people, although these groups do not predominate in the current outbreak), the infection may lead to a life-threatening disease, such as haemolytic uraemic syndrome (HUS).
6. Why is it affecting adult women in particular?
In Germany 61% of the EHEC cases and 70% of the HUS cases are in female (as of 3 June 2011). The reason is unknown, but it may be that adult women are more exposed to the source of contamination. It is very unusual to have such severe outcomes as HUS in young and middle-aged adults, as the normal high-risk groups are young children and elderly people. Some cases have also occurred in school-aged children.
7. Is there/will there be secondary transmission?
So far all cases but one have been in people who live in or who have travelled to Germany. One person has contracted EHEC due to contact with a visitor from Germany who was infected.
A person who has the infection can pass it on to someone else through poor hygiene, such as not washing hands after using the toilet and/or before handling food. Person-to-person spread is not unexpected with E.coli, it has been seen in previous outbreaks, for example in institutions.
8. What has been the source of past E. coli outbreaks?
- Processed meat from cattle in hamburgers, kebabs and salami
- Raw milk, cheeses
- Raw vegetables, such as coleslaw, lettuce, spinach, radish sprouts and alfafa sprouts
- Fruits including melons, and apple juice
- Contact with lakes, ponds, paddling and swimming pools (waterbone outbreaks)
- Direct contact with goats, sheep or other ruminants in petting zoos.
