Flu Basics

by DemFromCT

For the past few days, I've been over at Daily Kos posting on recent H5N1 developments (WHO Gets More Honest About Indonesia, Flu Stories: Indonesia Clusters Show Evidence Of H2H Spread and H5N1: A Teachable Moment, And An Open Letter) all of which involve some discussion of the Indonesian family that show strong evidence of human-to-human (rather than bird-to-human) spread of H5N1 flu. Although you can go there for details, I thought I'd use this opportunity to explain why this is important.

There are actually several different kinds of flu that get tossed around.

Seasonal flu is either influenza A or influenza B, and generally hits the US between November and March for around six miserable weeks. The onset date differs from year to year and location to location. The annual flu shot protects you from this year's seasonal flu only, and generally gives less-than-perfect results, particularly to the elderly. This is because flu changes from year to year. Because it takes 6 months to manufacture flu vaccine, a committee guesstimates which flu will be coming each year before the season starts. Some years they get it right, and some years they don't.

In fact, there are subtypes within the seasonal flus. Influenza A has the most variation, and is named by the proteins on the viral envelope. There's a hemagglutinin (the H protein), which lets the virus latch on to receptors on epithelial cells in the host's body. And there's a neuraminidase (the N protein) that lets the virus escape from the infected cells (see Flu Wiki's science section for more details). There are actually 16 different Hs and 9 different Ns; only H1 and H2 and H3 occur in humans but all of them occur in birds, the natural host for flu. This year's seasonal flu is an H3N2, for example and that's what's in this year's flu shot along with influenza B and H1N1 (more about that one later). But if you see a flu referred to by the H and N, it's influenza A.

If a novel H such as an H5 or H7 or H9 gets into a human, we have no defense against it because we've never seen it before. But birds have, and so these novel flus that exist in waterfowl and other birds (but not humans) are referred to as bird flu or avian flu (even though all flus are bird flus). The one circulating now in Asia and Africa and Europe in birds is H5N1, a particularly nasty character that kills more than 56% of those people who get it. While ducks and other birds can get H5N1 and live, it's especially deadly to chickens and domestic poultry. It's very difficult to catch, and even more difficult for humans to spread because the receptors in human airways for the current H5N1 are deep in the lungs of humans and not in the nose and throat. That's one reason why, when humans do catch it, the virus does a job on human lungs (but there are other reasons for why it's deadly, which I will not explore here, and which are not fully understood). And it helps explain why sneezing, involving the nose, doesn't spread H5N1 easily from human to human. Since H5N1 preferentially resides deep in the lung, it's not plentiful in nasal secretions and if spread, doesn't latch on to someone else nasal passages easily. Seasonal flus are much more easily spread and are very infectious.

We don't fully understand exactly how flu is spread, but the above basics apply. However, should something happen that would make a novel bird flu like H5N1 easier to spread, such as having the virus mutate to a form that likes the nose and upper airway receptors (so that it's easy to catch and easy to spread by sneezing), or prefers the temperature of the human nose, it could start to spread in a human population. If the combination of a novel virus that humans aren't immune to (from previous exposure) and easy transmission (due to factors such as are listed above), we could get a rapidly spread flu which, when it breaks out everywhere, is called a pandemic, an epidemic everywhere in the world. Pandemic flu, or panflu is the feared agent that causes a pandemic.

This has happened before. in fact, in 1918-9 H1N1spread around the world, killing 50 million people. There were milder pandemics in 1957 and 1968, and we really haven't seen one since, at least on that scale. But since we get around three each century, we are due, and that's why scientists say that a pandemic of some sort is inevitable.

The three flus (seasonal, bird and pandemic) are listed and compared here.

Now, the reason the news from Indonesia is so concerning is that we have a novel virus (H5N1) that has not just spread from birds to humans (B2H), but has spread in a family from human to human (H2H) and likely from human to human to human (H2H2H) or even perhaps H2H2H2H. This has happened on a small scale with H5N1, in Vietnam and Thailand. Although WHO has never been forthcoming about this, many of us think it's happened in Turkey and Azerbaijan. These clusters of infected relatives could be the beginning of the chain of infection that characterizes a pandemic - or a cluster could just burn itself out, as it did in Turkey, without further spread. Or, they could just be all the humans who got the virus from the same bird. For that reason, clusters always spark an investigation to let WHO or CDC (or whoever conducts the field study) what's going on. But only in the last few days has WHO flat out said H2H has occurred,even if rarely, and never in as big a cluster as in Indonesia and never in an H2H2H chain.

Furthermore, there are actions that are supposed to be taken should spread occur, such as giving everyone tamiflu, and quarantining contacts. This requires a great deal of cooperation and coordination, both of which are lacking in Indonesia. The worry is that if H5N1 starts to spread undetected, and mutates to an easily spread form, we could have a pandemic that could make 1918 look like a picnic - this, with an H5N1 flu virus that kills more than half of the people it infects (it killed 7 of 8 in the Indonesian cluster). this 'worst-case' scenario is what is the basis for the pandemic flu planning going on in the US. We have no vaccine against H5N1 and it would take 6 months to begiin to make some. It would take a year to get enough to be useful – and that's assuming the vaccine worked well (the current one in experiments works rather poorly). Oh, and some of the H5N1 strains are resistant to tamiflu, and in the best of circumstances, it must be given early and in high dose.

For further reading, I encourage you to visit the website of Peter Sandman and Jody Lanard, as well as the Flu Wiki,  which has many pages on preparation and planning. There are other good web sites as well, including www.pandemicflu.gov, which has a brief capsule of the Indonesia situation here, and Trust For America's Health. But wherever you get your information from, those are the basics. And understand that since we've never tracked a pandemic from before when it's happened, we don't know what to look for, exactly, or what the early signs are. Certainly, large clusters, health care workers getting ill from the patients they care for, or large numbers of reported flu-like illness are on that list.

And that's why Indonesia is important.

Please leave questions here and we will try to address them as best we can (we certainly don't have all the answers). And if I have not been clear in this basic review, check out the other sites listed, and start to educate yourself about what you want and need to know.

Comments

[emptypockets]

I've been meaning to ask you: I've seen a lot on how the 1918 pandemic started, but not much on how it ended. And I've been wondering when -- if ever -- we will know that the current situation is over. Was the 1918 outbreak eventually stopped by quarantines alone?

[DemFromCT]

Like the end of flu seasons, it seemed to just stop. The virus may have mutated to a milder form.

The best written source is John Barry's The Great Influenza.

As to when we'd know when it's over... the new cases start dropping in number, assuming we're capable of tracking it..

[free patriot]

wow, this is like "flu science for dummies", thanks. I've heard the data in a scientific form, and I couldn't explain it in english

It's like nighmare stuff, but it's real

I've heard people ask "what if" about the flu virus mutating with the hiv virus, and this kinda shows how that isn't a real possibility, and that the flu virus don't need no help to become a HUGE threat

all those "government conspiricy" people are gonna be dissappointed that this isn't coming from some secret government lab

mother nature just has it in for us

[notjonathon]

If I remember correctly, there was another pandemic in 1962-3. At least the three days I spent in a Tokyo hotel draining my precious bodily fluids made me feel that way.

Your article made it clear why this strain of flu is so deadly.

On the other hand, I read in one article (too long ago to find a link) that some people in areas where avian flu had struck had been afflicted with only mild flu-like symptoms, indicating that mortality rates might be lower than is apparent. Has any investigation been made into these reports, for example, have blood samples been taken of relatives and neighbors of victims and tested for antibodies?

[joejoejoe]

I just read that Indonesia has the first case of person-to-person-to-person transmission of bird flu. From the Malaysian Star (AP):

"But this case may mark the first time bird flu has passed from person to person to person, a top U.S. health official said. The previous clusters all involved someone who was infected by a sick bird and then spread the virus to others. This new cluster appears to involve a cascade of transmission, said Dr. Julie Gerberding, director of the U.S. Centers for Disease Control and Prevention, in a telephone briefing from Geneva."
http://tinyurl.com/h8oy4

This sounds like a big deal to me in terms of the speed and difficulty of containing any outbreak. What is your take on this development?

[emptywheel]

A great basic description of the stakes, DemFrom, thanks.

[DemFromCT]

notjonathon , the worst flu seasons are the ones where you get it. No, that wasn't a pandemic year. A real pandemic would be unforgettable.

joejoejoe, It's a huge deal. The first three links in the story directing you to Daily Kos are my take on it. it's not the start of a pandemic, but it's the next check on the checklist.

[Europepanflu]

Great job, DemFromCT. As you may see (blog link), Europe is not taking the "pile tuna" aproach - possibly expecting a mild pandemic?

If American citizens have friends over in Europe, please share your concerns with them.

[John Casper]

Great post, thanks DemFromCT.

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