Entries by Scott McPherson (410)

WHO speculates: "Dust" from wet markets causing human infections?

WHO spokesperson Gregory Hartl recently spoke of the difficulties in pinpointing the vector of human transmission of H7N9. This is from an Investor Business Times article from last Thursday:

“This is one of the puzzles still [to] be solved and therefore argues for a wide investigation net,” Hartl said. “It might be because of dust at the wet markets, it could be another animal source beside poultry, it could also be human-to-human transmission,” he said.

The idea of "dust" is not a far-fetched one, but it does warrant some explanation.  We know that viruses are also subject to the laws of gravity.  Virus particles will, inevitably, drop to the ground -- only to be kicked back up again when disturbed.  I alluded to this in an older post, from 2007.

During the SARS almost-pandemic, vacuuming of hotel carpets in China contributed to the spread of the disease.  The cruise ship industry's protocol when confronted with an outbreak of norovirus on a ship at sea includes the cessation of vacuuming.  And my lectures and presentations on pandemic preparations include this same advice.

It is entirely possible that "dust" from the floors of wet markets might have contributed to the incidence of human cases, but it still would not point us toward the source of the infections. Something/someone had to deposit that "dust" on the floor of the market. Clearly, the WHO feels that poultry remains the most likely candidate.  However, continued testing of poultry from wet markets in Shanghai and elsewhere have failed to find the "smoking chicken" everyone desperately needs to find, before this virus goes through enough mutations for find -- voila! -- a branch of this flu with the ability to move at will amongst humans.

And if the culprit is not poultry, then is there another vector depositing virus on the floors of, say, bus depots, other markets, hotels, restaurants, or newsstands?


China H7N9 cases climb to 106, deaths rise to 21

It was a busy weekend.  While America and Boston began its recovery from the horrible events of the preceding days, the situation in China worsened.

"Worsened" could be worse.  First, the Monday morning reset:  We have 106 confirmed human cases of H7N9 avian influenza.  We have a suspected confirmed human case in yet another province, Shandong.  And we still have no Earthly idea what (or who) the vector of transmission is.

But we still do not have the exponential growth (think of that old shampoo commercial) in cases that would signal the beginning of sustained human-to-human transmission of H7N9. 

Just one week ago, we had 72 human cases.  Friday, we had 91 cases.  And as I mentioned, today we have 106 cases.  Now the attention turns to what we don't know; namely, guessing how many unreported or undiagnosed cases there might be.

In the absence of previous testing, we are simply guessing.  As Spock said in Star Trek IV, they are making the best guess they can possibly make. From sleepless blogger Mike Coston's morning joe entry:

If, as these scientists suggest, there are really 200 cases out there, then the case fatality rate (now sitting at 20%) would be cut to (a still impressive) 10%.

We don't know when the infection started.  We don't know the carrier. We suspect wild birds have communicated the disease to poultry, but the number of positives found while testing eastern Chinese poultry probably is not that much greater than what you might find in the Netherlands or Germany.

And, believe me, they are testing poultry in Europe!  Flutrackers.com reports that H7 has been found in a turkey farm in Saxony.  27,000 birds are meeting their Maker. While low-path, as is the Chinese outbreak (if only in poultry), the Germans know the entire flock must be wiped out.

Back to China.  The virus has spread to yet another province, and Zhangzou has overtaken Shanghai as the province with the highest number of reported cases.

Veteran flu tracker laidback AL, he of the superb charts, brings us yet another gem.  The gem is flawed; it was created before Shandong came on the map. But it does show the new leader in confirmed cases, Zhegiang.

The mapo also shows the proximity of Shandong Province to the other eastern provinces.  From Wikipedia:

Shandong has emerged as one of the most populous (95,793,065 inhabitants at the 2010 Census) and most affluent provinces in the People's Republic of China (GDP of 3.94 trillion CNY in 2010).

Add another 95 million people to the mix of potential mixing vessels.

CDC begins actively looking for H7N9 in the United States

In a conference call this afternoon with clinicians, the U.S. Centers for Disease Control and Prevention has officially asked hospitals and doctors to begin looking for signs of human infection with H7N9 avian flu.

Some takeaways from the 2PM EDT conference call:

Persons exhibiting influenza-like illness and/or severe respiratory distress, and who have either traveled to China or have had close contact with someone who has traveled to China, need to be considered in a separate category and closely monitored.

Any Influenza-Like Illness within this subset that cannot be conclusively diagnosed as seasonal influenza needs to be considered suspected H7N9, and samples are to be sent to the CDC immediately.

Suspected patients should be put into isolation, preferably in an appropriate environment, negative-air-pressure room (AIIR).

It is unknown whether rapid office tests could detect avian influenza.  Therefore, all commercially available influenza tests should be disregarded when testing for H7N9. It should be assumed they are inaccurate.

The CDC is currently the only testing facility in the United States that can test reliably for H7N9.  This will change as the CDC certifies states with the ability to detect H7N9.

The CDC is advising organizations to review and revise their pandemic plans.

International airports with frequent travel to and from China have begun listing H7N9 information on their electronic signs, particularly in Customs areas.

Limited human-to-human transmission has occurred in China. Which is a) not surprising and b) probably expected.

Put people on Tamiflu immediately upon suspicion of H7N9, even if they have presented symptoms for more than 48-hours.

CDC can have test results within hours of receipt of the samples.

Clinicians need to collect specimens and notify their state health department for instructions.

There have been cases, as recently as March, where people tried to illegally smuggle Chinese poultry into the United States. 

(Of course, this was a concern back in 2007.  Recalal than in July, 2006, a Troy, Michigan warehouse was raided for suspicion of illegally-imported goose parts.  The boxes were later stolen from the Government-sealed warehouse.  )

This is getting real interesting real fast.

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.

China H7N9 update: 72 cases, 14 deaths. And the Chinese combat another viral incident (just not the one you think)

As the case numbers continue to climb, I found the most interesting article regarding another viral outbreak the Chinese are fighting -- viral social media.

This article sums it up nicely. Apparently the hot Chinese social media site is Weibo.  the Chinese are learning that the Internet, and accompanying social media, are forcing transparency. Good.