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I was re-reading some of my influenza texts last night (Kilbourne, Hope-Simpson, Kolata, et al), downloading swine flu data back into my head that I had not used in a couple of years. Some of the disclosures:

Swine H1N1 was actually given from humans to pigs, possibly back in Iowa in October of 1918, according to most experts. Swine H1N1 is a direct descendant of the 1918 Spanish flu bug. 

Swine H1N1 is believed to have caused the mini-pandemic of 1946, where the human H1N1 was supplanted by a much more virulent version that was genetically similar to swine H1N1.

Swine H1N1 is also suspected in the 1951 epidemic of the "Liverpool flu," which predated teenaged reaction to the Fab Four by twelve years. The Liverpool flu was an extremely serious epidemic, with mortality in some areas of Britain (get this) worse than the 1918 pandemic.

Revere of Effect Measure blog wrote an excellent piece on the Liverpool epidemic back in 2007. The blog referenced a scientific paper on the epidemic, written by NIH's Cecile Viboud and her co-authors. Here is a digest:

Influenza activity started to increase in Liverpool, England, in late December 1950. The weekly death rate reached a peak in mid-January 1951 that was ~40% higher than the peak of the 1918-19 pandemic, reflecting a rapid and unprecedented increase in deaths, which lasted for ?5 weeks (see figure). Since the early 20th century, the geographic spread of influenza could be followed across England from the weekly influenza mortality statistics in the country's largest cities, which represented half of the British population. During January 1951, the epidemic spread within 2 to 3 weeks from Liverpool throughout the rest of the country.

For Canada, the first report of influenza illness came the third week of January from Grand Falls, Newfoundland. Within a week, the epidemic had reached the eastern provinces, and influenza subsequently spread rapidly westward.

For the United States, substantial increases in influenza illness and excess deaths were reported in New England from February to April 1951, at a level unprecedented since the severe 1943-44 influenza season. Much milder epidemics occurred later in the spring elsewhere in the country.

Local disparities were found in all 3 countries, with a consistent pattern of higher numbers of deaths in locations affected earlier. In England, influenza-related death rates were ~3-fold higher in Liverpool than in the rest of the country. In Canada, death rates were ~2.4-fold higher in the eastern seaboard provinces than in the rest of the country. Similarly, in the United States, rates were ~2.3-fold higher in New England than in the rest of the country.

I was also watching and listening to comments made by my friend Dr. Mike Osterholm of CIDRAP. Mike, as you can imagine, has been a very popular fellow lately. Mike reminds us all that if this virus does go pandemic, we are by no means "off the hook" in terms of lethality if the first wave is mild.

Veteran flu watchers all recall that in 1918, the spring wave of H1N1 was very mild. It was the second wave -- cooked in the summer and fall of 1918, in the trenches of WWI -- where the virus gained its ability to kill by the millions. And it was the third wave that incapacitated President Wilson (NOT a stroke, but Spanish Flu in April 1919) that allowed the punitive actions of Britain and France against aggressor Germany to move forward, and sowed the seeds for the Third Reich. That is your history lesson for today.

A swine pandemic was feared by experts long before the 1976 swine flu debacle. This is what caused the major calamity that we now call the Swine Flu Debacle.  This new strain, with its curious mixture of swine, avian and human genes, is headed for an uncertain future.  But we cannot simply assume that a lack of mortality or lethality is necessarily good news in the long run. 

A group of 22 college students and 3 teachers traveled from Auckland, New Zealand to Mexico. The trip, a language-oriented trip, lasted three weeks.  The return trip funneled the students and faculty through Los Angeles Bradley International Airport.

Upon returning home, the students began complaining of flu-like symptoms.  Testing immediately took place, and at least ten of the students have "untyped A" influenza.

A quick primer for new readers:  The rapid test for flu can determine any of the known strains of influenza A or B.  If a teat comes back "untyped A," the protocol calls for that sample to go to the appropriate central testing organization.  In the US, that is the Centers for Disease Control. 

The New Zealand tests showed untyped A.  So far, that has meant swine H1N1.  Since this new flu strain has a more rapid incubation period (from 1 to 3 days, according to the WHO), these students were shedding virus at least from LA to Auckland.  Everyone on board the airliner was, in all probability, exposed to virus.

The situation in Mexico City continues to escalate. In an unprecedented move, President Felipe Calderon has declared a public health emergency, activating a sweeping array of powers.

From the Bloomberg.com news story:

Authorities have canceled school at all levels in Mexico City and the state of Mexico until further notice, and the government has shut most public and government activities in the area. The emergency decree, published today in the state gazette, gives the president authority to take more action.

“The federal government under my charge will not hesitate a moment to take all, all the measures necessary to respond with efficiency and opportunity to this respiratory epidemic,” Calderon said today during a speech to inaugurate a hospital in the southern state of Oaxaca.

Museums, theaters and other venues in the Mexico City area, where large crowds gather, have shut down voluntarily and concerts and other events canceled to help contain the disease. Two professional soccer games will be played tomorrow in different Mexico City stadiums without any fans, El Universal newspaper reported. Catholic masses will be held, the newspaper said, although church officials urged worshipers to wear breath masks and to avoid contact.

Schools will likely remain closed next week, Calderon said in the Oaxaca speech. The decree allows Calderon to regulate transportation, enter any home or building for inspection, order quarantines and assign any task to all federal, state and local authorities as well as health professionals to combat the disease.

“The health of Mexicans is a cause that we’re defending with unity and responsibility,” Calderon said. “I know that although it’s a grave problem, a serious problem, we’re going to overcome it.”

Also, there is now an Obama link to the epidemic. On April 13th, the apparent first day of the epidemic, well--- you read it yourself. Also from the Bloomberg story:

The first case was seen in Mexico on April 13. The outbreak coincided with the President Barack Obama’s trip to Mexico City on April 16. Obama was received at Mexico’s anthropology museum in Mexico City by Felipe Solis, a distinguished archeologist who died the following day from symptoms similar to flu, Reforma newspaper reported. The newspaper didn’t confirm if Solis had swine flu or not.

So the President of the United States -- the leader of the Free World -- was possibly exposed to a pathogen without his knowledge.  It's almost like an episode of 24. 

You can't miss this.  I'll let their words speak.

http://news.bbc.co.uk/2/hi/talking_point/8018428.stm

I have been looking at the geographic dispersion of Mexican confirmed and suspected swine flu outbreaks.  From Mexico City to Baja back to central Mexico and down to the southwestern Pacific corner of the nation, there are literally hundreds of suspected cases of respiratory distress. 

Of course, not all of these will be confirmed swine H1N1.  But as the California flu hunter said yesterday, the more they look, the more cases they will find.

And as has been dutifully blogged by me and by others, the CDC has already thrown up its arms and declared the virus is beyond its capability to contain -- even with only (so far, soon to be obsolete) eight US cases in its portfolio.

So here's the situation, put as clearly as I can possibly put it:  Either this virus will burn itself out, or it will go pandemic.  It is that simple, and those are the only two options available.

If it burns out, it will be due to a combination of factors, including trying to slow it down and getting in front of it.  But keep in mind that 75% of all influenza pandemics start outside of regular flu season.  Part of that reason is because there is no competition for hosts with other, more established flu strains.

As I have said many, many times before:  Influenza plays "king of the mountain."  It is Darwinian struggle at its clearest.  Flu bugs fight each other for supremacy.  Eventually, one wins out.  Of course, this model was disrupted, perhaps permanently, in 1977 by a Soviet lab accident that released a descendant of the 1918 Spanish flu upon the world, creating that "age-specific pandemic" that affected anyone born after 1956.  Prior to 1957, H1N1 was the dominant flu strain.  In 1957, H2N2 knocked H1N1 off the mountain.  And it was in turn knocked down, in 1968, by H3N2.

Back to today: In the Northern Hemisphere, H1N1 swine flu today has dramatically reduced competition for hosts.  Flu season is essentially over, and seasonal influenza is retreating to wherever it is that it retreats to.  This leaves a clear path for swine flu to find susceptible hosts and infect them en masse.

To its credit, the Mexican government, it appears, has done a commendable job getting masks to its citizens and antivirals to the epicenters of the outbreaks.  Its surveillance capabilities may be called into question in retrospect, but its response seems to be well-planned and immediate.

It is now fish-or-cut-bait time for American flu planners.  And as many risk communication experts will tell you, now is not the time for mixed messages.  We cannot tell people to prepare for a pandemic with an Asian origin and then not tell them to get prepared for one with a Latin origin.  The waiting game won't work, especially when the virus has penetrated our defenses.  It's time to tell people how to get ready and what to do, if we are to have any hope of burning this out before it jumps the oceans -- unless we're too late already.

But it's worth a try.