A new eco-perspective on preventing an epidemic: How H1N1 compares to SARS and the Nipah virus

Skyline-smBy Aaron Bernstein, MD, MPH, physician in Medicine at Children’s and faculty, Center for Health and the Global Environment

Sometimes the best perspectives come from far away places and few places are farther from Boston than Singapore, a small yet highly developed island nation in southeast Asia where I spent much of October.

The distance between Boston and Singapore is more than geographic, however. While I was away, H1N1 reclaimed the national spotlight back home. Not a day went by without mention of it in the news. It became the topic of conversation among doctors and patients everywhere. Well, almost everywhere.

While everyone in Singapore knew of H1N1, it was hardly the hot topic it had become in the States. During my stay, the main paper in Singapore ran just one article on H1N1 informing its readership that the first vaccine doses wouldn’t arrive for several more weeks.

To my surprise, the Singaporeans I met took this news in stride. One reason for this is that many Singaporeans perceive (and rightly so) that H1N1 is, in many ways, no worse than the seasonal flu that comes every year.  In addition, Singaporeans have endured two much more deadly epidemics in the past decade, making H1N1 pale in comparison. In 1998, the first known outbreak of Nipah virus occurred in Malaysia and Singapore infecting 276 people, 105 of whom died. In this and eight subsequent outbreaks in India and Bangladesh the virus has earned the grim reputation of being one of the deadliest viruses known, with a mortality rate between 40 and 80 percent. Nipah virus resides in bats (the “reservoir”, as bats do not get sick when infected). Bats infect pigs, and exposure to infected pigs causes disease in humans.

In 2003, severe acute respiratory syndrome (SARS) emerged in China and quickly spread to Singapore where it infected about as many people (238) as Canada (251) and far more than in all of the United States (27). The SARS virus reservoir is also bats, which transmitted the infection to humans via the palm civet cat. The mortality rate for SARS was about 6-17%. In comparison, the flu mortality rate is well below 1%.

This comparison is not made to belittle H1N1 and its ill effects. But if you’ve seen viruses like SARS and Nipah, H1N1 doesn’t look so bad.

Being in Singapore helped me identify another dimension of the H1N1 pandemic. H1N1 turns out to be a mutt of a virus, containing genes from bird and pig flu viruses. Some of the present H1N1 pandemic strain genes likely originated in birds that live in southeast Asia. Recognizing that all three of these viruses – SARS, Nipah and H1N1 – have roots in southeast Asia should spur consideration of the conditions that make that corner of the world a crucible for emerging diseases.

For Nipah virus, the rapid expansion of pig farming had a hand in the disease’s emergence; for SARS, the dietary diversity of some Chinese, who eat a variety of exotic animals, played a key role in stoking demand for palm civet cats in outdoor markets where they commingled with an astonishing array of creatures. Farming and diet, however, only pertain to the intermediate hosts – pigs and cats. Still other and perhaps more significant contributions may come from what has been happening to the viral reservoirs.

Imagine for a moment that you were in charge of preventing the spread of H1N1. Would you put an infected person in a small room filled to capacity with uninfected people? Likely not. And yet, this is precisely what is occurring in Southeast Asia where rates of deforestation are some of the highest in the world. As habitat dwindles for the birds and bats that carry viruses that may infect humans, their populations concentrate, probably increasing the likelihood that they will spread viruses among themselves and in turn, deliver them to us.

Ultimately to prevent epidemics like H1N1 we need ample supplies of hand sanitizer, masks, medicines and vaccines. But if we are wise, we can steal some of the H1N1 spotlight to focus attention of public health officials on the connection between ecological changes half a world away and public health back home.