[health-vn] The pandemic threat

[Vern Weitzel]

http://www.economist.com/opinion/displaystory.cfm?story_id=13576183


Pandemics
The pandemic threat

Apr 30th 2009

 From The Economist print edition

It’s deadly serious; so even if the current threat fades, the world needs to be 
better armed

Illustration by KAL

IT IS said that no battle-plan survives contact with the enemy. This was 
certainly true of the plan drawn up over the past few years to combat an 
influenza pandemic. The generals of global health assumed that the enemy would 
be avian flu, probably passed from hens to humans, and that it would strike 
first in southern China or South-East Asia. In fact, the flu started in an 
unknown pig, and the attack came in Mexico, not Asia.

The hens, though, deserve some credit. The world has not had a pandemic (a 
global epidemic) of influenza since 1968. Four decades are long enough to forget 
that something is dangerous, and people might have done so had they not spent 
the past ten years considering the possibility that a form of bird flu which 
emerged in Hong Kong in 1997 might be one mutation away from going worldwide.


The new epidemic (see article) was raised on April 29th to just one notch below 
the level of a certified pandemic by the World Health Organisation. In an effort 
to halt the spread of the disease, Mexico’s president, Felipe Calderón, has 
announced that non-essential services should close down between May 1st and 5th, 
and people should stay at home. Part of the reason for worry is that, unlike 
ordinary flu, which mostly carries off the old, the victims of this disease are 
mostly young and otherwise healthy.

Still, this epidemic has not actually killed many people yet. That there have 
been a mere handful of confirmed deaths is probably the result of a lack of 
proper tests. But even if all the possibles are counted in, a couple of hundred 
fatalities cannot compare with the 30,000 deaths caused in America each year by 
seasonal influenza. So how scared should we be?

Damned if you do, damned if you don’t
As far as this epidemic is concerned, it’s too early to tell. One unknown is how 
widespread the virus is in Mexico. If it is ubiquitous, and had not been noticed 
earlier because it emerged during the normal flu season, then this epidemic may 
turn out to be insignificant, at least to start with. No flu death is welcome, 
but in this case the new disease might not increase the immediate burden 
greatly. But if the new strain is relatively rare, or what is being seen now is 
a more dangerous mutation of what had once been a mild virus, then the 
proportion of infected people dying may already be high. The death-toll, then, 
will rise sharply as the disease spreads.

Either way, the authorities were right to hit red alert. Influenza pandemics 
seem to strike every few decades and to kill by the million—at least 1m in 1968; 
perhaps 100m in the “Spanish” flu of 1918-19. And even those that start mild can 
turn dangerous. That is because new viral diseases generally happen when a virus 
mutates in a way that allows it to jump species, and then continues to evolve to 
exploit its new host. If that evolution makes the virus more virulent, so much 
the worse for the host. HIV, the AIDS-causing virus, lived happily and benignly 
in chimpanzees before it became a scourge of people. In Mexico, the early 
indications are that two pig viruses that can infect people but rarely pass from 
person to person recombined with each other to create a virus which does so easily.

Changes in virulence have certainly happened before in influenza epidemics, 
which have struck in successive waves of different severity. The message is that 
it makes sense to put money and effort into containing the new infection even if 
it does turn out to be relatively harmless today. The more people who have the 
virus, the more virus particles there are for that one, fatal mutation to appear in.

Resistance is another reason to try to contain an epidemic early. New antiviral 
drugs that were not around during past epidemics seem to be effective against 
the current outbreak. But natural selection is a powerful force, and if the 
spread of the disease means they have to be used widely, a resistant strain of 
the virus could easily evolve.

Don’t wait till winter
Now is the time to prepare for the worst. Flu—including pandemic flu—tends to be 
seasonal. The infection will probably tail off in the north over the next few 
months and head south as winter gets a grip on the Earth’s less populated 
hemisphere. It would make sense, therefore, to put the antiviral factories on 
overtime immediately, and try to develop, manufacture and distribute a vaccine.

Crash vaccine programmes pose their own risks. In 1976 flu vaccines killed a lot 
of people in America. But the growth of biotechnology means there are new ways 
of making vaccines and new types of vaccine to make. Mostly, these have been 
aimed at the threat of bird flu. But laboratories will already be clearing the 
decks to receive their first samples of the new swine flu, and getting to work 
on countermeasures.

And there is one further lesson. The system of checking for new diseases also 
needs to be improved. Partly because everyone was looking at Asia, no one was 
concentrating on Mexico. But as genetic sequencing becomes cheap and routine, it 
ought to be possible to pick dangerous mutations up quickly.

That would mean sending samples from doctors’ surgeries to a central laboratory 
dedicated to sequencing, even when nothing strange was suspected. And that would 
require organisation and money. Not every person with a sniffle need be 
tested—only a small, representative sample. But if this had happened in Mexico 
over the past few months, the generals of global health would have seen that 
something was coming down from the hills and they could have mobilised sooner.

Active caution, then, is what is called for. The world’s policymakers, most of 
whom live in the northern hemisphere, should not be fooled into thinking the new 
virus is going away for long, even if it declines over the next few months. 
Instead, as in any phoney war, they should use the time they have been granted 
to reinforce the world’s defences by stocking up with antiviral medicine and 
making vaccines. They should also remember that, even if this flu turns out to 
be less frightening than feared, it is only a matter of time before a deadlier 
one comes along. A drill today will help to spare millions of lives in the future.