Sars: what's the worst case scenario?
Thursday April 24, 2003
Millions dead. Although the disease is spreading more slowly than the Spanish flu pandemic that killed up to 50 million people in 1918, it is more lethal and may simply take longer to spread. There are two big reasons the disease could get badly out of hand: no one is immune to Sars, and there is no effective treatment.
"It's unprecedented that there's a new virus we have absolutely no immunity to, so there's a potential for it to become a total global epidemic," says Peter Openshaw, an expert on respiratory diseases at Imperial College in London.
"Even with containment, I don't see any reason why it should fizzle out. It's not spreading as fast as the Spanish flu did, but that doesn't mean it's not spreading as surely." A vaccine, which would be the most effective defence against Sars, is likely to take 12 years to develop, he adds. This week the World Health Organisation (WHO) is due to bring in experts to model the likely course the outbreak will take. The answer is anyone's guess, says Dick Thompson of WHO. "This is a new disease. We don't know where its going to go. We don't know how it's going to evolve."
Many people infected with the Sars virus have been administered anti-viral drugs, antibiotics and steroids. But as yet there is no proof that anti-viral treatments are effective. Antibiotics are also ineffective against the Sars virus, as they are against any virus, and are given only to treat secondary bacterial infections the patient may pick up. Steroids can be effective in reducing lung inflammation, the ultimate cause of death in those infected with Sars.
Coronaviruses account for between 5% and 30% of common colds, and as a result we have antibodies that can combat certain types of the virus. But because the Sars coronavirus has never been transmitted to humans, we do not have antibodies against it.
According to WHO, two regions will dictate how bad the spread of Sars becomes. One is the developing world. Because surveillance for the disease and health care systems are poor, the disease could rapidly become rife. "If it gets in there, it may be impossible to dig out," says Thompson. The second region is China. Even though Chinese health officials have started reporting real numbers of infections, it is too early to know how widespread Sars is there. "We don't know what's really going on in China," says Thompson. "We have a much better idea than before, but we think they are only now getting good reports."
The WHO is also looking out for so-called tertiary infections. These are infections that cannot be traced back to someone known to be directly exposed to the virus. If the trail fails to find who spread the infection, the outlook is bleak. "It can mean it's out there in the community, that there are people without symptoms that are spreading it," says Thompson.
Intriguingly, the virus seems well-adapted to spreading through modern hospitals. "With most viral infections, once you are sick, the virus is on the way out," says Openshaw. "This is most infectious when the disease is most severe." That means it is most likely to spread when people are fussing over you.
As of April 22, the WHO said 3,947 people in 26 countries were infected with Sars. Of those, 229 had died while 1,935 remained ill.