Initial reports from Indonesia indicate that bird flu has infected several pigs. If confirmed, the incident would mean the chances of the virus' breaking into the human population have slightly increased.
Samples taken from 10 pigs near Kubu Simbelang in Sumatra have tested positive for a bird flu virus, Indonesian Agriculture Minister Anton Apriyantono said May 18. Six bird flu cases in one family were previously reported in the same village. Apriyantono did not specify whether the virus was the H5N1 strain that has aroused much angst of late, but did note that reconfirmation testings are still being carried out. Right now, H5N1 is not a significant health threat to human societies because the virus is unable to jump from one human to another. The only people at significant risk from H5N1 are those who come into extremely regular, extremely close contact with fowl — a list that boils down to developing-world chicken farmers. Limit that contact, and the chances H5N1 will infect someone drops precipitously. As knowledge of the mechanism of bird flu infection spread during the past year, the impact on human cases was easy to discern. In 2004 and 2005, there were 141 cases of human H5N1 in Vietnam, while so far in 2006 there have been none. But much more than simply human cases matters. If H5N1 cannot jump into a human, then it is extremely unlikely it would ever mutate into a form capable of easily jumping from one person to the next. At present, no cases of human-to-human transmission have been confirmed despite what media hype might imply. Barring a dramatic mutation, H5N1 is an agricultural threat, not a health threat. Assuming the incident is what it appears to be — the infection of 10 pigs by H5N1 — then the possibility of an H5N1 human pandemic has increased. Pigs have a great deal in common with humans from a genetic standpoint, making them a potential petri dish for viral evolution that could impact people. Since pigs and humans share greater genetic similarity than birds and humans, viral evolutions in pigs are more likely to cause problems for humans than similar evolutions in birds. And while health authorities' ability to track human cases in rural Sumatra is weak, their ability to detect swine cases is certainly worse — and the possibility exists for H5N1 to become endemic in a nonhuman-mammal population that could serve as a generator for virus strains eventually culminating in a human-to-human transmissible version. There are few worse places where this scenario could happen. Vietnam was not unique in its ability to educate and therefore vastly reduce its bird flu cases in humans: similar results have been achieved in Cambodia and Thailand. But Indonesia's territory is vast, its government efforts thin, its communication infrastructure weak and its ethnic tension palpable. In short, it is not a location where central edicts about agricultural safety easily percolate to the rural dweller. The chances of H5N1 being the virus that turns into a global human pandemic are still quite small. Nevertheless, if the Indonesian reports are true, those chances just got a little bigger.