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I have watched the White House press briefing three times now. There are some things which stood out for me.

Encapsulated: We do not know if we are watching the first infant signs of an epidemic, or if by some strange stroke of Fate we are already experiencing the "first wave" of an epidemic or pandemic. We have not tested enough people prior to April 1 to get a handle on that answer. No one has.

Why not? Simply, the symptoms were not severe enough for anyone to suspect that another strain of influenza was at work -- at least, not until Mexicans started dropping dead in significant numbers. Then, and only then, did the next, more sophisticated level of testing take place.

In 2009, it is (regrettably) common for people not to be tested for influenza if they go to their family doctor. I, for example, have never been swabbed for flu -- and I have had several different doctors treat me for different respiratory ailments over the past two decades. If you don't swab, you can't test. If you don't test, you can't type.

It is this lack of serious illness that worries us in Egypt, and in Indonesia, and in other regions where H5N1 has become endemic. There is absolutely no way to determine the level of penetration of a virus without testing blood for antibodies. This is precisely the exercise the Egyptian government and the WHO are collaboratively taking with human samples -- to look for antibodies to avian H5N1 and to see if the disease has asymptomatic carriers.

We won't know if this swine variant has been with us for awhile until many months from now.

I am wondering if the comment from DHS about the number of swine flu cases abating, and then picking up again after a few weeks, is actually code for the USanticipating a wave of a pandemic. This would make sense if you view the big picture of the US response. The increased surveillance is obviously meant to see how widespread and how rapidly the virus is moving. The pre-positioning of antivirals is not just to be ready to treat mildly sick Americans -- it is also meant to quickly treat deathly ill Americans in case the virus evolves quickly and begins to attack with as much lethality as it appears is currently taking place in Mexico.

Let me take you back to 1918.Back then, the prevailing opinion was that flu was a bacteria and not a virus. Also, influenza was not a "reportable disease" like it is now. There were many, many cases and a lot of deaths, but nothing near what was to come.

It was the second wave that got everyone's attention. And then the third and final wave came, which was milder than the second but worse than the first. Then H1N1 settled into the lexicon of seasonal viruses.

Let's look at the current rate of deaths in Mexico. A quick bit of calculus can tell us how many cases may be underreported in Mexico. If we look at 80 deaths and 1400 cases, we see the Case Fatality Rate (CFR) somewhere between 5 and 6 percent. If the CFR were something much more reasonable -- say, 1% -- then we are looking at some 8,000 cases.

Influenza's goal is not to kill its hosts. It is to coexist with its hosts. Even the 1918 pandemic's CFR was somewhere between 2 and 2.5% of those infected. Still, if the CFR in Mexico is at 1%, then the virus is far more widespread and the chances for an epidemic are magnified exponentially.

Also, the fact that young adults are dying is the worst news within this current onslought of reports. These people just are not traditionally ill. Only testing and autopsies will tell us if the dreaded "cytokine storm" of immune overload is at work here.

People will remind you that there is a ton of respiratory disease and malaise in Mexico. I would counter that we have a whole new subclass of Americans -- immunocompromised Americans with HIV/AIDS, cancer patients undergoing chemotherapy, and other autoimmune diseases. These people especially need to stay very, very close to what is taking place right now.

Regarding the release of antivirals from the SNS: I was fascinated to see the military preposition Tamiflu so quickly (some 7 million courses, or 700,000 boxes of ten capsules). This action tells me that the federal government is itself unsure if this is an early outbreak, or if surveillance broke down and we are a lot further along in this episode than anyone realizes. The absence of data is so glaring, and there is not a doggone thing anyone can do about it until we have more data, better data and good sequencing of the genes of this new virus.

That is key. Labs such as St. Jude need to see this new virus, and see the Mexican clade that is killing people, and see if it is antigenitically the same, or if a mutation occurred that would make the virus more lethal than its American counterpart. In my opinion, this will ultimately decide if borders close, or if travel is curtailed.

This opinion appears to be shared by the WHO itself, in the person of one Keiki Okuda. Here is an excerpt from anew article from Sky News:

Swine Flu Could Become More Dangerous

The swine flu virus that has killed more than 80 people in Mexico may mutate into a "more dangerous" strain, the World Health Organisation has warned. Skip related content

"It's quite possible for this virus to evolve... when viruses evolve, clearly they can become more dangerous to people," said Keiji Fukuda, of the global health watchdog.

Mr Fukuda also called for international vigilance as health experts wait to see whether the virus will turn into a worldwide pandemic.

Over 1,300 people are now thought to have contracted the virulent H1N1 swine influenza after it mutated into a form that spreads from human to human.

The Mayor of New York has confirmed that eight school children are suffering mild symptoms after becoming infected.

And there have been at least 12 other confirmed cases in Texas, Ohio, California and Kansas.

The White House has declared a public health emergency but told the public "not to panic".

Sky US correspondent Greg Milam said: "It's important to realise that those affected have only had mild symptoms, and all have recovered or are recovering.

"But the authorities do believe that this outbreak will get worse."

Canada has become the third country to confirm human cases of swine flu with six people falling ill in Nova Scotia and British Columbia.

Elsewhere in the world, suspected cases have been reported in France, Spain, Israel, New Zealand and the UK.

In France, two people who had returned from Mexico with fevers are being monitored in regions near the port cities of Bordeaux and Marseille.

A 26-year-old Israeli man has also been admitted to hospital after returning from a trip to Mexico with flu-like symptoms.

In Auckland, 10 school children have tested positive for influenza after returning from Mexico.

In the UK, two people have been admitted to a hospital in Scotland after returning from Mexico last week.

They are said to have mild flu-like symptoms but their condition is not causing concern.

Mexican City Mayor Marcelo Ebrard said two more people have died of the virus, taking the death toll to 83.

Overall, I am impressed with the acting head of the CDC, Dr. Richard Besser. He evokes confidence and I think he is believable. Why? Well, for one reason, he wanted to pounce on certain questions and had to restrain his movement until his "handler" -- the White House press secretary -- either gave him a nod ormotioned him toward the podium with a deferential wave of his hand. If this press conference was his audition for the top job at CDC, I think he passed.

The White House briefing on the swine flu crisis was relevatory.  Besides declaring a nationwide public health emergency, the White House has ordered a release of 25% of the Strategic National Stockpile of antivirals Tamiflu and Relenza to the states, with prioritization to those states with outbreaks and confirmed cases.  Additionally, the Department of Defense -- and don't be alarmed, because the SNS is a joint project of HHS and DoD -- anyway, DoD has already pre-positioned some 7 million courses of antivirals.  Who do you think guards all those warehouses?  Guards from 24?

We now also know that Ohio has reported its first case.  No word on the suspected Minnesota and Massachusetts cases.

Daily briefings will occur until the crisis has passed, the duration of which is entirely up to the virus.

New York Mayor Bloomberg has just announced that the eight suspected cases of swine flu at a local private school are confirmed.  The eight cases are part of a student trip that just returned from Mexico.

Bloomberg is urging sick New Yorkers to stay home.  Always sound advice.

The White House is scheduled to brief the press and public on American plans just after noon EDT today.

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.