Trust is not transitive, as someone recently pointed out, when reporting on the airline pilot who carried a gun into the cockpit and then accidentally or negligently discharged it and blew a hole in the plane. We had every reason to trust the pilot to be able to fly a 747, but not necessarily to handle a firearm properly. Trust isn’t transitive.
There is no doubt that Yi Guan, a professor at the University of Hong Kong, is an expert on H5N1 virus, its genetic lineages and surveillance for the virus in wild birds. He has reportedly screened, via cloacal swabs and fecal specimens, more than 200,000 wild and free ranging aquatic birds and poultry in China since 2000. So if he has an opinion about whether proper surveillance can stop a pandemic it is reasonable to listen to what he says and consider it seriously. But it is not necessarily reasonable to trust his judgment because he is an expert at the lab bench in using surveillance specimens. Because once Guan talks about a pandemic he is talking about a global scale outbreak of disease in human beings. That involves epidemilogy. So I am slightly skeptical of a pronouncement by someone whose speciality is surveillance of birds, not the epidemiology of influenza in people:
“For disease control, surveillance must be a long term effort. You know where it is and you know it is coming, like a spark of fire you can extinguish it,” Guan said.
“If not for all this surveillance and detection ability, the pandemic would probably have already come.”
Drawing from what is known of past pandemics, Guan believes that surveillance and strict control measures are the answers.
“Pandemics don’t happen suddenly, they have an early phase, mature phase, outbreak phase. The virus changes step by step, it takes a long cooking time,” he said.
“If a virus gets into humans in the early phase, the transmission ability is very low. At most, they infect their families, but it can’t go further into the community.
“This phase is the golden point to control. Once it matures and becomes (efficient in) human-to-human (transmission), it will be too late.” (Tan Ee Lyn, Reuters)
My own view, as an epidemiologist, is that this proposition is highly unlikely. Even in Guan’s specialty, we know very little about the movement of the virus. How does it get from one place to another? What is the role of poultry movement versus wild birds? (What are the routes of poultry movement and how do we follow and control them? What are the migratory routes of wild birds? (We only know this in very broad generalities, not at the even fairly coarse resolution that we need to control the virus if birds are a mode of movement, numerous maps, notwithstanding; you will find these maps are based on scant information and many inferences, insufficient for what would be required to really know and understand bird movements globally). Nor is surveillance for the virus complete, effective or comprehensive. That’s just for starters.
There’s also the question of human epidemiology. At the molecular level we don’t know what makes the virus transmissible (we have clues, only) or virulent (still only clues) or pathogenic (still more clues). In humans we still aren’t sure of the relative importance of different modes of transmission (large or small droplets, fomites, possible undiscovered animate vectors). Where does the virus hang out in nature? Are their additional reservoirs besides poultry and wild birds? What accounts for the seasonality? Where does the virus go in the “off season”?
Even taking Guan’s conjecture in its strongest possible form, that we know enough about these missing data points to say that stopping a pandemic was possible through surveillance alone, there are the obvious questions about public health in the Real World. Public and veterinary health are grossly under supported and things are getting worse, not better. The international system that supports cooperation between countries cannot even make the half century old influenza virus surveillance system work, much less impose the kind of interference in “national sovereignty” that would be required to snuff out an incipient pandemic even if we knew it was coming. What surveillance can do is warn us to get ready, not be the firewall that prevents the invasion.
Yi Guan is a genuine expert in the virology of H5N1 and an expert in the Art of Surveillance as we now practice it. Surveillance is of supreme importance in global preparation to face a potential pandemic with a very dangerous virus. But just because it is his opinion that the hammer he wields will hit all the nails on the head doesn’t mean that a good hammer is even close to being a sufficient tool even under the best of circumstances.
Trust isn’t transitive.