Pandemic Surprise - The Monster at Our Door: The Global Threat of Avian Flu - page 33

al features that made it more amenable to control through public health measures than some other poten-
tial emerging infectious disease threats.” 129 In the first place, SARS needs about five days to incubate and
does not usually become contagious until well after the onset of fever and dry coughing; infectiousness
takes about ten days to peak, and research has found few asymptomatic infections without sickness. The
old-fashioned tactics of isolation and quarantine, if ruthlessly implemented, can work effectively against
such a slow-developing virus whose symptoms consistently signal infectiousness.
Influenza is an altogether different story. It is fast and deceptive, and infectiousness and sickness do
not coincide; an infected person massively sheds virus and becomes highly contagious a day or more be-
fore the actual onset of symptoms. (HIV, with its long, silent incubation period is, of course, even more
insidious because the infected person can be contagious for years without manifesting any symptoms or
sickness.) Moreover, influenza epidemics include large numbers of asymptomatic infections: spreaders
without symptoms. Influenza, as a result, is more transmissible. In addition, technically it has a higher
“R” or “basic reproduction number” (defined as the “average number of secondary cases generated by one
primary case in a susceptible population”) than does SARS, or for that matter, HIV. A typical flu has an
R of 5 to 25 while SARS is only 2 to 3 (not counting the still poorly understood phenomenon of so-called
superspreaders). To stop an epidemic of SARS, public-health officials need only block viral transmis-
sion, either by isolation or quarantine, in about half the cases. Control of pandemic flu, on the other hand,
requires an almost 100 percent containment of infection. 130 Traditional isolation measures, accordingly,
may not be much more effective tomorrow than they were in 1918.
Finally, the 2002-3 SARS pandemic had a fortuitous geography. China and Singapore were both au-
thoritarian states with the capacity to impose effective, militarized quarantines. (In Singapore this took
the Orwellian form of temperature-detecting sensors in the airport and home video-surveillance of hun-
dreds of quarantined individuals.) Guangdong, moreover, by Chinese standards is a rich region with a
much more modern health-care infrastructure than poorer inland provinces. Although SARS exposed the
Achilles heel of neglect and underinvestment in their public-health systems, Toronto and Hong Kong are
likewise affluent cities with superb laboratory medicine.
SARS in Bangladesh, Afghanistan, or Zaire would have been a different pandemic. This is exactly the
“What if?” that haunted the Royal Society's postmortem on the SARS pandemic: “[S]uppose the virus
had flown from Hong Kong to Durban instead of Toronto. It is a city of similar size but without a similar
health infrastructure, and with a significant proportion of its inhabitants immune-compromised owing to
HIV-1 infection. Then Africa could have become endemic for SARS by now.” 131 An influenza pandemic,
to be sure, would not neglect the poor countries of the world.
* The ever doughty Jiang was subsequently arrested in June 2004 after circulating a letter asking the government to
apologise for the Tiananmen massacre.