It seems swine flu is full of surprises that turn out not to be surprises. Or so it’s claimed. Or not. Here is CDC’s Dr. Anne Schuchat, the agency’s chief health officer and spokesperson on swine flu, responding to NPR’s Melissa Block’s question about what has been her biggest surprise:
Dr. SCHUCHAT: I shouldn’t have been surprised, but I have been surprised about this disproportionate toll that it’s taking in pregnant women. I think I’d never lived before a pandemic before, and I actually hadn’t seen the really sorry and just the tragic stories of healthy pregnant women coming down with such difficult diseases.
So that’s been hard to take as a public health expert, and, of course, a reason that we strongly recommend pregnant women who have cough or fever, respiratory symptoms, to take that seriously and seek care and get antiviral medicines and, of course, to be vaccinated before they get such symptoms. (National Public Radio, interview November 25, 2009)
I like the way Schuchat answered this. Flu is notoriously unpredictable and it can do almost anything, including things we have seen in the past or expect it to do on the basis of reasoning. With so many plausible possibilities, almost any outcome will be deemed in hindsight to be unsurprising. In hindsight. Even so, we are (properly) surprised, and she (properly) admits to it.
Yet every time something vaguely worrisome happens — like the emergence of antiviral resistance — it’s dubbed “not a surprise.” For antiviral resistance, there’s nothing surprising about it and a couple of dozen reports of Tamiflu resistance are already on record. Almost all, however, emerged during treatment and were not “epidemiologically linked,” i.e., didn’t show evidence of having been transmitted from one person to another. The resistant infections “dead ended.” This is an important issue because the property of being resistant is separate from the property of being able to be passed easily from person to person. Resistance doesn’t spread until you have both.
The virus is already highly transmissible, of course, so it would seem that only one mutation is needed, but as we’ve discussed here before, the eight genetic segments of the flu virus work together as a team, and when one team member changes character in a way that seems by itself to be beneficial to the virus it often happens that it degrades the overall objective of making copies of itself. That’s one of many reasons why predicting what flu will do by just looking at the genetic sequence is a chancy affair. An apparent, although not conclusive, instance of a transmitted resistant strain was reported by CDC in July involving two young summer campers in North Carolina. Within the last week two further clusters indicating person to person transmission, one in hospitalized patients, again in North Carolina, and another in five hospitalized patients in the UK (Wales). So while there have a couple of dozen cases of resistant isolates previously, now it seems we are seeing clusters indicating there is a resistant form that is also transmissible. That’s a change.
And in the last day or so a sixth person has been added to the UK cluster:
The sixth patient is linked to five people who last week became the world’s first confirmed cases of person-to-person transmission of such a strain.
Another person in direct contact with the group at University Hospital of Wales, Cardiff, has been tested.
In the Tamiflu-related cases, three patients remain in hospital, with one in critical care and the other two treated in isolation.
Dr Roland Salmon, director of the National Public Health Service for Wales’ Communicable Disease Surveillance Centre, said it was “not unexpected” that more patients on a unit treating people with severe underlying health conditions would test positive for the Tamiflu-resistant strain. (BBC)
So it’s not unexpected that it’s “not unexpected” that a unit treating people with severe underlying conditions would test positive for a resistant strain, because “not unexpected” or “not surprised” is the norm — after the fact. Presumably the patient’s underlying medical condition allows the virus to replicate more quickly or more profusely, thus promoting the chances of a a sloppy copying mistake by the virus that accidentally makes it resistant. Presumably. And presumably the fact they may have been immunocompromised (some are reported to have suffered from blood cancers) suggests easier transmission because it lowers the barrier to being infected on the other end. So on reflection, not a surprise. The answer to everything.
After it happens.