BRIAN DEER:
MATTHEW AND THE BURGER BUG Page 3
By
this time, the investigation of the Morecambe cluster
had enlisted the big guns of science. As Telford's
technicians confirmed each case as an O157 infection,
a sample was posted to the government's Central
Public Health Laboratory in Colindale, north London,
and an e-mail was fired weekly to the Communicable
Disease Surveillance Centre, which is based at the
same site. The central laboratory, which was founded
in 1946, has an annual budget of £10m and employs
some 400 staff. It is the nerve centre for tackling
infectious diseases, such as Aids, tuberculosis and
meningitis.
The
lab's scientists have published cutting-edge research
on E-colis of every description. The core of these
bacteria are minute tube-like cells, which have been
classified through proteins in their skin (so-called
"O" antigens) into 173 different sorts.
Radiating from these cells are little tails, or
flagella, which in turn are classified by another
antigen ("H"), of which 55 have so far been
found. Going a stage further, the O157:H7 organism,
involved in the recent British outbreaks, has been
sorted into around 80 different types, and the most
modern technologies can go even deeper and
fingerprint its DNA into thousands of individual
strains.
Compared
with other infectious agents, O157:H7 is not that
common, but it is causing anxiety among scientists
because it is incomparably nastier than most. It is
astonishingly resilient: able to live in the kind of
conditions that would kill other bugs. On farmland,
it can survive in the soil for up to six months,
while in kitchens it can cling to cool, dry surfaces
and shrug off many household cleaners. Unlike
infections such as salmonella and campylobacter,
which require millions of bacteria to cause human
sickness, as few as a dozen of the new E-coli are
needed. And when it strikes old people, or children
of Matthew's age, it can leave them in a critical
state.
Rachael's
sons' samples, along with the other children's, were
sent to Colindale for what is called "phage
typing", which can give clues for investigating
outbreaks. Using a handle-cranked contraption on a
second-floor laboratory bench, technicians stamp
dishes of E-coli with 16 viruses which attack
bacteria. By later reading which viruses attacked
what, the organism in the dish is given a
rough-and-ready type. In the Lanarkshire outbreak,
for example, where cross-contaminated ham had been
sold by the local butcher, Scotland's equivalent lab,
at Aberdeen, identified each patient's specimen as
containing a type 2 E-coli bug.
But
Colindale's typing of the Morecambe cluster produced
a startling result. Matthew's and Tom's specimens,
along with the 11-year-old boy's, came up as type 2.
The six-year old girl's, however, was typed 8. The
girl aged 14 months who had been abroad was
apparently infected by type 34. And there was a 21
and a 32 as well. Since an outbreak should involve
bugs of the same type, it seemed that, whatever the
source of Rachael's sons' infection, it was not the
same as all of the others, despite the links of
place, time and age. It looked as if the cluster was
only a bizarre coincidence.
The
environmental health officers took this as good news:
there was no Lanarkshire-style outbreak on their
patch. Brownjohn and Mann felt that nothing further
would be gained by carrying out any more inquiries.
No food or other samples were taken from Rachael's
home. The nearby allotment, where the children picked
apples, was not investigated for infected manure.
And, although both she and her boys regularly mixed
with other children and parents, no contact-tracing
was done to check the possibility of person-to-person
spread. Even in the face of Matthew's deteriorating
condition, the investigation was brought to an close.
But,
far from being grounds for confidence, the hidden
story of the Morecambe cluster may have been more
disturbing than even the Scottish crisis. It is
hardly credible that an infection judged to be so
rare that doctors, laboratory staff and environmental
health officers give it scant attention should strike
eight children in one place and at the same time
without any explanation. It is possible that either
the phage typing was wrong - and insiders say it
often is - or, if they were infected with different
types, then that suggests there is more E-coli around
than has so far been acknowledged. In short, that
Morecambe was the tip of some iceberg of hidden,
unreported, infections.
The
clue that there may have been more to know is found
in statistics compiled at Colindale by the
Communicable Disease Surveillance Centre. During the
week that Matthew became ill, these showed a dramatic
and unexplained leap in O157 reports. In the week
before the first day of his illness there were 24
notifications in England and Wales - more or less
last year's weekly average. In the week beginning the
Monday after, Day 8, during which he was admitted to
hospital as an emergency, there were more: 52
reports. But during the seven days between - the week
ending September 19 1997 - the numbers pouring in
from labs such as Telford's totalled a staggering
103.
What
this spike in the graph points to may have been a
national outbreak which was not so connected by
geographic location to come to local authorities'
attention. With foodstuffs often transported hundreds
of miles from central processors and packagers,
Rachael's boys may have been connected to many others
by exactly the kind of "low-level
contamination" which the Morecambe investigators
had suspected. "We felt we were seeing a local
aspect to a national problem," says a member of
the local team. "Intuitively, we felt that was
the best bet."
A
review of the evidence stacked up so far supports
this intuition. Most infections in healthy adults
produce no or only minor symptoms. Most hospital labs
do not routinely test for E-coli, so its true
incidence is unknown. No statistics are compiled on e
coli-related disease. And the number of deaths cannot
be calculated because certificates rarely cite the
infection. With the bug's resilience and ability to
trigger illness in extreme low doses, it could easily
have got into a mass-market product last year, been
distributed throughout the UK during September and
caused apparently unconnected sickness in children
from Land's End to John O'Groats.
If
Matthew was the victim of such events, the central
laboratory could expose the fact. But again the child
was let down by a system that undervalues the E-coli
threat. Although Colindale's phage typing sounds
impressive and is carried out on all samples received
at public health laboratory's labs, it is a cheap,
quick, crude and virtually clapped-out technology,
devised half a century ago to classify salmonella.
More than one third of all O157 strains are lumped
together in this system as type 2 - far too big a
group to track through the food chain. And although
the more sophisticated DNA fingerprinting technique
is available at Colindale, it is not routinely used,
on grounds of cost.
Once
more it was question of the priority for E-coli - and
whether the specialists and authorities that are
charged with fighting it are doing everything that
the public would expect. "Everybody has limited
funds," says Tom Cheasty, a senior researcher at
the central laboratory. "The way we are financed
and staffed, we couldn't do all the work that would
be needed to be done on everything. We wouldn't have
enough hours in the day. If people spent more time
looking at this bug they would have to spend less
time looking at some of the others."
But
the new fingerprinting technique (called
"pulsed-field gel electrophoresis") could
have analysed the DNA in Matthew's and Tom's samples
and not only matched the precise strain of the
organism present against the other Morecambe
children's, but also against those involved in all of
the other infections reported to north London that
week. Each family affected could have been
interviewed as Rachael was and common sources readily
identified, wherever in Britain they might be.
To
fingerprint all of that week's 103 samples might take
a technician three months and cost £6000, but such
DNA testing combined with new methods of detecting
the organism in foodstuffs and bar-code tracing of
products through the food chain, could transform the
response to E-coli. Not only could rogue producers or
packagers be nailed, but also bad practices at
abattoirs, dangerous activities such as spraying
animal remains and cattle faeces on farmland, and the
continued sale of high-risk milk, could all be
swiftly tackled. Some scientists believe there would
be the long-term chance of eliminating the bug
altogether.
Although
Colindale cites the pressure of other work, the main
beneficiaries of not using the new technologies may
not be other research priorities, but the giant food
and farming enterprises whose lapses may remain
undetected. If tests linked disparate cases of
illness such as the Morecambe victims' with batches
of common products, such as, say, ham or milk, public
opinion could force severe government action, as it
did over BSE. And after the wholesale slaughter of
cattle brought about by inquiries into two dozen
human deaths from new variant CJD, business could be
forced into another round of costly remedies to clean
up its act.
But
if the winner is business, the loser is the consumer
- leaving parents such as Rachael to think that
illness must be due to something in the home. On the
day that Brownjohn called and interviewed her, the
things that stuck in her mind most strongly were
questions about her habits. Which shelf in the
refrigerator do you put cooked meats on? Do you
always clean knives after cutting? Could you show me,
please, how you wash your hands? Let me look at the
kitchen again.
Brownjohn
left her thinking that she was to blame for the state
of her little boy's health.
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