Wednesday, July 8

H1N1/swine flu: How to mask the failure of CDC's approach to fighting a pandemic

I see WHO has moved the goal posts again:

July 8, 2009:
The World Health Organization will recommend that nations curtail efforts to confirm swine flu cases and assume the H1N1 virus is the culprit.


Meanwhile, the virus is continuing to spread through the Northern Hemisphere this summer -- even though flu normally doesn't spread well in hot weather -- and its effect is growing in the southern half of the globe, which has begun its traditional winter flu season.


Within the next few days, the WHO will suggest that countries with major outbreaks of swine flu move away from laboratory confirmation of cases and toward larger, national indicators of disease, such as the number of people with flu-like symptoms and cases of pneumonia, Dr. Keiji Fukuda, WHO assistant director-general, said Tuesday in a telephone news conference.

The large number of cases in such countries is overwhelming labs and making it "very hard to keep up" with testing, he said. The new guidelines will "ease the burden on laboratories," he said. In most countries with major outbreaks of the virus, 95% or more of total flu cases are being caused by H1N1.

"In countries with no cases, we will continue to recommend that people be tested so the presence of the new virus can be confirmed," Fukuda said. "In all countries, we will continue to stress testing for unusual cases, clusters, unusually severe cases and new symptoms."

But the number of swine-flu-free countries is likely to be small soon. The most recent figures reported to the WHO indicate that more than 98,000 cases have been confirmed in 120 countries, with 440 deaths, though officials estimate the number of actual infections at 10 to 100 times that. [...]
A big thanks to Photoshop artiste "Freedom Fairy" for sending me the above report.

Now why is WHO making such a recommendation? Why are they trying to influence how each individual country collects data on swine flu cases? The rationale WHO provided in their 'pre-announcement announcement' goes nowhere near answering that question.

WHO has no political teeth, and in the swine flu outbreak it has played the caboose to the CDC (U.S. Centers for Disease Control and Prevention) and governments that contribute the most to WHO's upkeep, such as the USA.

The CDC has, from the earliest weeks of the swine flu outbreak, encouraged U.S. health departments to abandon swine flu testing for all but the hospitalized cases. This approach was copied by Australia and several other countries, which have substituted mathematical modeling (based on very uncertain data) to project the number of swine flu cases, in lieu of extensive laboratory testing.

It's been hard enough up to this point to get even a rough estimate of the number of swine flu cases in a country; if the majority of countries follow WHO's planned recommendation, that will make it virtually impossible to pursue an empirical approach to studying the swine flu outbreak on a global basis.

Researchers will have to rely on whatever mathematical models a country's federal health department favors. As to how much faith can be placed in the models:

On July 3 Freedom Fairy alerted me that the Drudge Report had posted a group of scary headlines about swine flu including this one: "40 a day could die by end of summer in London," which linked to a report in the United Kingdom's Mail Online newspaper.

The prediction was based on math quoted by Britain's Health Minister, Andy Burnham. He announced to the House of Commons on July 2 that swine flu "Cases are doubling every week, and on this trend we could see more than 100,000 cases per day by the end of August -- although I stress that that is only a projection."

This elicited a remark from John Oxford, the professor of virology at St. Bart's and Royal London Hospital who's been a favorite quotable source for reporters since the swine flu story broke:

"It seems like a lot of mathematical modeling and not too much common sense."

But just to make sure Mr Burnham understood how math-challenged he was, an editor at Effect Measure blog got instructive:
The statement that the UK might have 100,000 cases a day made headlines, as well it might. But it's based on the idea that if the current exponential growth rate continues for months on end, then it could reach 100,000 a day by the end of August.

Anyone familiar with exponential growth and/or epidemiology (is it too much to hope a Health Minister might be familiar with both?) knows that exponential growth cannot and does not continue for very long.

If cases double every week, then by the end of September, one month after Burnham's estimate, they will have increased by a factor of 16 or 1.6 million cases per day. A month later, at the height of flu season we'd be seeing 25 million cases a day. [U.K. population: 60,943,912 ]

Of course if you put E. coli in a petri dish and watch it double every 20 minutes, before long all the mass in the known universe would be incorporated into the E. coli culture you started.

Did I mention this doesn't happen? Ever? What a bloody moron.
I believe the more precise operative term is "useful idiot." Mr Burnham is young (39), new on the job, and (as with his American counterpart, Kathleen Sebelius) spectacularly unqualified by education and experience to hold a post relating to public health, medicine, science, or math of any kind. His previous posting was Secretary of State for Culture, Media and Sport; he was appointed Secretary of State for Health in Gordon Brown's June 5 Cabinet reshuffle.

However, the troubled expression on Mr Burnham's face (see the video of his announcement at the Mail link) suggests he's old and smart enough to have figured out that he is Labor's designated sacrificial goat, if Britain's death toll from swine flu skyrockets.

So if Mr Burnham was guilty of bad math, at least he mustered enough survival instinct to strongly warn the British public that swine flu is not to be taken lightly. And he surely knew by last week what has only come to public light today: "Swine flu: Scots will be forced to wait 1½ years for full vaccination."

All right; I've had enough fun for one day with Britain's health ministry. What's really going on with WHO? Well, Ouija is out for repairs again but taking a blindfolded shot in the dark:

"From April 25 to July 5, a total of 8,272 people entering China with flu-like symptoms were transferred to medical institutions for quarantine. Some 228 of them were confirmed as H1N1 flu patients."

The report doesn't say whether the statistic refers only to the Mainland or to the combination of the Mainland, Hong Kong territory, and Macau. But because the announcement came from the central government's Ministry of Health, I'm going to tentatively assume it covers all three regions, which is not ideal for my purpose. However, the statistic gives a rough idea of how many people have been quarantined on the Mainland. Now watch carefully don't blink:


Population: 1,338,612,968

May 10
Mainland China reports their first confirmed case of swine flu, an infected Chinese citizen traveling on a flight originating from the USA..
June 01
Confirmed swine flu cases: 38
July 7
Confirmed swine flu cases: 1,151

Confirmed death toll from swine flu as of July 7: 0
(One death by accidental electrocution of a Chinese patient in quarantine).


Population: 21,007,310

May 09
First confirmed case of swine flu; an infected American airline passenger traveling on a flight originating from the USA.
June 01
Confirmed swine flu cases: 401
July 07
Confirmed swine flu cases: 6,353

Confirmed death toll from swine flu as of July 7: 18

I'm not picking on Australia; I'd prefer to pick on my own country. But I used Australia as the comparator because it's a modernized, economically advanced democratic country and the date of their first confirmed outbreak is close, by one day, to the Mainland's.

I note that Australia's health system was quickly overwhelmed by swine flu cases. From a June 13 report:
Angry GPs have slammed a "conspicuous lack of leadership" in Australia's response to the swine flu crisis, with some patients waiting eight days for test results or receiving anti-viral drugs too late to limit the infection.

The number of Australians infected with the new H1N1 strain is ... believed to be far higher than last night's official national tally of 1391 because Victoria [state] has abandoned its daily caseload updates.

The state last Wednesday cut back its laboratory testing for the virus from about 500 to 1000 samples a day to 50 to 70 a day, after acknowledging it could no longer contain the disease.

Even then, patients were falling through the cracks in the testing system, Melbourne GP Kirstin Charlesworth told The Australian. [...]
All this means the comparison is unfair to China, which up to this point has scrupulously tracked down and recorded every swine flu case they could find in the country. But when you compare the data, there's the answer to WHO's observation that China's strategy for fighting swine-flu is "resource intensive."

Yes, if only one country does it, the strategy is very resource intensive, both in terms of money and labor. But China's strategy worked to greatly slow the spread of swine flu infections in their country; Australia's strategy didn't do the same for their country.

With few exceptions Australia's experience has been echoed by every country that's been hit by an outbreak.

Governments can stack and rack their excuses any way they want -- and I interject there have been some very creative excuses. But they are up against the reality of China's accurate record-keeping -- a feat China pulled off because their way of fighting the pandemic was to greatly limit its spread at the start. That doesn't mean they caught every case. It means they caught every case that came to the attention of a physician or hospital.

Australia's strategy for coping with a pandemic virus is a copy of the CDC one, which WHO has also followed.

The CDC pandemic-fighting model is based largely on analysis of the 1918 swine flu pandemic. China's model is based on empirical observations of the way 'airborne' or aerosolized infectious disease first spreads from country to country in the 21st Century; namely, via globalized, heavy-volume commercial airline travel.

There is no way to erase the data on China's success at doing the Number One thing a national pandemic fighting plan is supposed to do: greatly slow the spread of the disease in a country. But there is a way to downplay the data, to bury it in plain sight:

If every other county abandons laboratory testing for all but clusters of infections and "special" cases, this will skew the country-by-country data on swine flu infections to such an extent that China's data on swine flu becomes meaningless as a comparator.

1 comment:

Barnaby Dawson said...

Its very possible that China is not being entirely honest about the number of swine flu cases. There are other factors that might be at work including demographic differences and climatic differences.

I think the WHO are right to suggest these countries stop routinely testing. The numbers that testing produces are meaningless beyond the very beginning of an epidemic because the testing labs are hopelessly overwealmed by the number of cases. Much better to count influenza like symptoms and test a representative sample of these (+some testing for scientific purposes). That would give a solid base for estimating numbers infected/dead, demographics, risk factors, CFR etc. We really need to know this informatiom.

You say that mathematical modelling is imprecise. This is true, however, relying on testing only would be truly hopeless. At least statistical estimates based on randomized testing and extrapolation are likely to give us the correct order of magnitude for our estimates. Relying on laboratory tests is guaranteed to underestimate the true numbers by huge margins.

The question is not should we use mathematical modelling but which model(s) shall we use?

The USA never had any hope of keeping swine flu out of the country. It was in and spreading before we'd even heard of the disease.

Whether it would have worked for other countries I don't know but I'm inclined to suspect it wouldn't have. Note that Singapore also tried this containment strategy (as did Japan) but Singapore now has a very high number of infections and Japan has more than China is reporting.