It has been slightly over a week since my earlier post on the Streptococcus agalactiae (GBS) outbreak in Singapore. There have been several initial news reports, and the Ministry of Health released a carefully worded message on 13th July stating that they were investigating the outbreak along with the Agri-Food and Veterinary Authority of Singapore (AVA) and National Environment Agency (NEA), and that “there has not previously been any proven link between eating fish, raw or otherwise, and GBS disease”. Channelnewsasia released another report yesterday evening, including a short video where a young healthy man with GBS septic arthritis of the knee was interviewed, along with short excerpts of interviews with various doctors, including myself. I believe the patient got the message across better than all the doctors in the video report!
From conversations with colleagues, it seems clear that the outbreak is still ongoing. More than 30 patients with recent severe GBS infections have been questioned on fish consumption (not systematic questioning!), with apparently more than 70% having consumed raw fish (yu sheng) from porridge stalls prior to hospitalisation, according to the Channelnewsasia report. That is an incredible statistic, especially once one understands that there are background cases of severe GBS infections occurring every week as well, which are unrelated to the ongoing outbreak. Going by the MOH statistic provided in their earlier statement, one of the larger hospitals had already experienced a 40% increase in the number of severe GBS infections by the end of June, relative to the whole of 2014.
All the previously mentioned caveats against raw fish and GBS are still true as of now, i.e.:
- GBS has not been found or reported in bighead carp previously.
- GBS also causes invasive, fatal disease in fish – in fact, it is usually detected only as a result of an investigation into unexplained fish dying off. It has been difficult to find reports where GBS only colonises fish. Fish with severe infections would probably not have been sold in Singapore hawker stalls.
- People have been eating raw fish in Singapore – prepared virtually the same way – for decades, and have had few issues (certainly none observed with GBS until now).
- Far more people eat raw fish locally and do not come down with invasive GBS disease (the attack rate would be very, very low if the association is indeed true).
Balanced against the continued rise in GBS severe infections (and a proportionate increase in those that have consumed raw fish from porridge stalls), how does one decide when to make a call warning against raw fish (yu sheng) consumption? I am certainly glad not to be in the respective MOH investigating officer’s shoes:
- Warn against raw fish consumption, get it wrong, and there will be angry porridge stall owners (with substantial income loss) and public derision.
- Delay against warning until there is concrete proof, and there may be more patients with severe GBS infections each week (perhaps each day), a few of whom may die or suffer severe morbidity, and again there may be public displeasure.
From a personal and professional perspective, however, the choice is easier. I like to eat raw fish from porridge stalls – in the past, perhaps once every month or so. I deem the risk sufficient that I will wait for MOH to announce the results of its investigations before indulging again. I have warned friends and family members against eating raw fish from porridge stalls at this point in time, and also patients if and when they ask. It certainly seems wrong on a personal level not to do so even if many links in the scientific chain of evidence are missing, if one is not prepared to eat the fish oneself because of the perceived risk of infection, having enjoyed it up until the recent past!
How does one account for the fact that many people eat raw fish and relatively few come down with GBS disease? If the raw fish hypothesis is true, it may well be a question of bacterial burden (i.e. how much infected/colonised fish is consumed), the fact that it is unlikely that ALL bighead carp are infected/colonised with this outbreak strain of GBS (several porridge stalls have been implicated, making it more likely to be an “upstream” – i.e. fish supply/source – issue than unhygienic practices at one stall), or some hitherto unknown immune defect, or a combination of the above.
Healthcare personnel should recognise that this is a current ongoing problem and facilitate MOH investigations if they do happen to diagnose and treat a patient with severe GBS infection in the near future. I believe MOH has alerted all the public sector hospitals to notify cases and collect data, but perhaps not all private sector doctors have been thus updated.
The most common question I get nowadays with regards to this issue is whether sashimi and sushi are safe to eat. As far as I know, it is with regards to GBS. At least I am still eating these. There is a concern of fish substitution in the markets and restaurants of many countries for some years (i.e. passing off cheaper fish as more expensive fish – fish fraud). I am unaware if this happens in Singapore with any regularity.