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47,801 swabs of poultry, just 39 positives -- so where's the virus?

Helen Branswell of the Canadian Press is all over the evolving H7N9 situation.  Today, she asks the question:  Where is the virus?  Because it certainly is not in Chinese poultry. As Branswell writes:

International health officials are scratching their heads over the paucity of positive bird tests for a bird flu, especially given that the human case count is more than double the number of positive bird findings. As of Wednesday, 82 people had been infected and 17 had died.

"Something is happening out there that's not being picked up," says Gregory Hartl, spokesperson for the World Health Organization in Geneva.

"It argues for the fact that we have to continue to cast the investigation net widely."

Xinghua, the official Chinese news service, reported just today:

BEIJING, April 17 (Xinhua) -- Animal infections of the H7N9 avian flu have only been detected in live poultry markets and a single wild pigeon, agricultural authorities said Wednesday.

Of the 47,801 samples collected from more than 1,000 poultry markets, habitats, farms and slaughterhouses across the country, 39 samples have tested positive for the virus, the Ministry of Agriculture said in a statement.

Of the 39 positive samples, 38 came from live poultry markets in east China's Jiangsu and Zhejiang provinces, central China's Anhui Province and the city of Shanghai.

A wild pigeon tested positive for the virus in Jiangsu.

The virus has not been detected in pigs, the ministry said.

But in the end I came away convinced that Hong Kong is taking this very seriously. They have to. They've seen what a new infectious disease can do.

Wherever the virus is, it ain't showing up in chickens.

Or is it? Branswell further writes:

Those findings beg the questions: Where is this bird flu hiding? And is China targeting the right species when it goes looking for H7N9?

Infectious diseases expert Michael Osterholm agrees with the suggestion that at this point, investigators need to keep an open mind about where the virus may be coming from.

But the director of the Center for Infectious Diseases Research and Policy at the University of Minnesota says too little is known about how China is testing for anyone to be confident that all the negative bird tests were true negatives. He suggests more information is needed before people can feel sure that the results being reported are truly as puzzling as they seem.

"There are just a number questions here that we can't answer yet based on the available information," Osterholm said in an interview.

"I think the Chinese have been very forthcoming in providing the results. I think the question now is how to interpret these results… based on how they got the results."

Osterholm says the questions that need to be answered are: What types of tests are being performed on samples taken from animals and how well are those tests doing at detecting the new virus?

To put this in context, one needs to understand that there was no on-the-shelf test for this H7N9 virus, which is a constellation of bird flu genes that hadn't been seen before.

Veteran readers of this blog know of my friendship with, and immense respect for, Dr. Mike Osterholm.  I think he is on to something here. We have a novel virus that we were totally unprepared for.  We have little capability for testing for the presence of the disease.  The testing reagents are literally just off the truck.  And the Chinese are ramping up a lot of spare labor to go out into the differne regions of the country to test.

I do not know just how difficult it is to swab a chicken's anus, and I am thinking there must be a hidden joke in there somewhere.  Anyway, I am thinking of the old Dean Martin Roasts on TV.  Once, Lucille Ball said, "Dean, you rub me the wrong way."  Martin quipped:  "I didn't know there was a wrong way!"

But I, as usual, digress. I had no idea there was a wrong way to swab a chicken's cloaca.

Mike Osterholm is saying that we are mising something.  So is Hartl.  What is it that we are missing?  Pigs are negative.  Chickens are negative.  

Crof had a great blog entry this morning.  In it, he posts the Good Morning, America report of Dr. Richard Besser.  Dr. Besser, as you may recall, ran the CDC during Wave One of the Swine Flu/pH1N1 Pandemic. Here's part of what he said, observing first-hand the "testing" of live poultry as it was being imported into Hong Kong:

Then the first truck of chickens pulled in to be screened. A team of around 15 agricultural workers wearing white coats, rubber boots, surgical gloves and face shields descended on the truck. One worker cut off the seal that had been placed on the door to the truck at the poultry farm in Guangdong Province. Then with the speed and precision of an army drill team, they went to work.

They selected 30 chickens at random from the thousand or so in the truck. Each bird had the same fate: a sample of blood was drawn; a cloacal swab was obtained; and the bird was returned to its cage. The whole operation from the time the truck pulled in to when it departed with a fresh seal took no more than 30 minutes. By law, the seal cannot be removed until at least five hours later, when the rapid testing for H7N9 is completed.

But I still have a few unanswered questions: How good is the rapid test for H7N9? And is testing 30 chickens enough? Perhaps you need to test more to be certain that the flock is clean.


As of noon today, we stand at 88 confirmed cases and 17 deaths.

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