With the weather cooling and the kids back in school, the media coverage of the H1N1 flu - last spring’s “swine flu” - is building back to a fever pitch, if you’ll pardon the pun. As expected, colleges immediately found themselves dealing with campus outbreaks, and elementary and high schools have also already seen flu cases in the first few days of the school year.

In April, scientists knew very little about the nature of this novel H1N1 strain, and the worst-case scenarios suggested by some flu experts fueled the frenzy over whether this virus could be as deadly as the 1918 pandemic that killed as many as 100 million people worldwide. Now, six months later, there has been a lot more time to study the virus, observe its movements through the Southern Hemisphere’s flu season, develop and test vaccines and estimate the damage us citizens of the Northern Hemisphere can expect as a our flu season traditionally begins in October.

Because the novel H1N1 pandemic is such a fast-developing and important topic, much of the research into it is happening at an accelerated pace and is being disclosed to the public more quickly and openly than is typical for the traditionally slow march of science. Other sites have done excellent overviews of influenza in general and what we know about this particular strain or have followed every turn of this story. Below are summaries for a few of the main H1N1 subtopics.

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Much of the latest news on the H1N1 virus, colloquially known as swine flu, indicates that the next flu season has the potential to be unusually rough. In some ways the last flu season never really ended; the Centers for Disease Control and Prevention report that 20 states are still seeing widespread or regional flu activity, with H1N1 accounting for the vast majority of cases.

The coming flu season could fall within normal ranges, but CDC planners are bracing in case it resembles an especially bad pandemic year, such as 1957. The details on how H1N1 affects patients are still coming in. Certain populations appear to be at high risk for severe symptoms and, occasionally, death. Widely covered today was a Lancet report that suggested pregnant women may be more susceptible to the virus, with a higher rate of hospitalization and an elevated death rate in the pandemic’s early days. Between mid-April and mid-June, six pregnant women (including one in Chicago) died from the novel flu strain, 13% of the 45 American deaths reported during that time period.

The authors of the Lancet paper recommend that pregnant women receive antiviral medication, such as Tamiflu, as soon as possible after developing flu symptoms - none of the six deceased patients addressed in the paper received antivirals until at least 48 hours after illness onset.

But the best way to protect pregnant women from the flu strain when it likely returns in force this fall is through vaccination. The H1N1 story of the summer has been the frantic race by governments and scientists around the world to have a vaccine against the strain ready in time for the Northern Hemisphere’s next flu season. Manufacturers told an FDA panel last week that about 100 million vaccines could be ready in the U.S. by mid-October, but with roughly 300 million Americans, not everyone is going to be immediately vaccinated and priorities will have to be set.

That sober reality set the stage for a fascinating meeting today in Atlanta, where the federal Advisory Committee on Immunization Practices - a panel of doctors, scientists and public health experts - attempted to pick and choose which groups deserved the first crack at the limited vaccine supply. Given the numbers released yesterday, it was no surprise to find pregnant women in the top priority group for this fall’s vaccinations. Also given priority in the ACIP’s recommendations were caregivers for children younger than 6 months (who cannot themselves be immunized), healthcare and emergency medical personnel, children and young adults from 6 months to 24 years old and adults with chronic medical conditions.

Added together, that’s about 150 million people, roughly half the U.S. population. But with compliance among the priority groups expected to be far below 100% (it’s only around 40% for the regular old seasonal flu), it’s thought that the initial batch of 100 million will suffice, even if each person needs two doses to be fully protected, which experts predict may be necessary. As more vaccines become available, people between 25 and 64 will get it next. Those above 65 years old, who have seemed less affected by H1N1, are in the third, lowest priority group.

Much of the debate Wednesday (helpfully webcast on the government’s flu.gov website) centered over whether the younger population targeted in the first wave of vaccinations should be capped at age 19 or age 24. The argument of some panelists: college kids are as good at spreading viruses as they are at sleeping in late. Others argued that colleges are also an excellent distribution system for getting vaccines to this particular population. So young adults will join the front of the queue for the first batch.

The effects of H1N1 on different age groups appear to vary in a striking way, according to epidemiology discussed at the meeting. With nearly 44,000 American cases of H1N1 now documented, elderly folks appear to be less susceptible to the strain than younger populations. That observation runs counter to the pattern in most flu seasons, when senior citizens are more sensitive to the effects of seasonal strains and thus are heavily encouraged to get the yearly vaccine. At a CDC press conference announcing the panel’s recommendations, Assistant Surgeon General Anne Schuchat urged American seniors to get the seasonal flu vaccine as usual this coming fall. But for the H1N1 vaccine, they’ll be at the back of the line behind their children and grandchildren.

(Not to be a scaremonger, but for a gripping tale of H1N1 overseas, see this article by New York Times reporter Sheryl Gay Stolberg and her daughter Olivia Robinson, who contracted the virus while on a school trip to China)

Ever since the swine flu outbreak hit, Patrick Wilson has been immersed in what he calls “emergency science.”

The emergency may have abated thanks to the low mortality rate observed from the H1N1 strain, but Wilson’s group is working with scientists at Emory University and the Centers for Disease Control and Prevention to help combat the novel flu variety.

Wilson’s skills suddenly are in high demand because of a paper he co-authored in the journal Nature last year, demonstrating a rapid method of making antibodies to specific types of flu. The technique one day could help protect against new pandemic strains for which a vaccines do not yet exist. In the short term, the method offers a new way of rapidly diagnosing cases of H1N1 flu.

“The first application the CDC wants is to make a rapid diagnostic,” said Wilson, an assistant professor in the department of medicine at the University of Chicago.

The method that Wilson’s team published last year could be a new chapter for an old way of dealing with infection through “passive immunization.” The idea of harvesting antibodies for sick patients began in 1891, when Emil von Behring and Shibasaburo Kitasato cured a patient with diptheria by injecting serum from sheep that had antibodies to the disease. Von Behring later won a Nobel Prize as “The Founder of Serum Therapy.”

Before the advent of antibiotics, such treatments with antibodies became widely used for many infections, including anthrax and Streptococcus pneumoniae.

“Doctors used to keep vials of antibody serum that they could use off the shelf for various infections,” Wilson said.

The risk of anaphylactic shock and other drawbacks of antibody serum made doctors turn to antibiotics and vaccines once they became widely available. But even today, the idea of using antibodies has appeal for emerging viral infections, for which scientists have not yet developed a vaccine.

Flu vaccines typically take months to make, but the technique that Wilson devised with colleagues from Emory and the University of Oklahoma Health Sciences Center can produce monoclonal antibodies to a specific strain of flu in just a few weeks.

No one knows yet if the flu antibodies would offer meaningful protection in the case of an emerging pandemic. Wilson said it’s possible that the technique would prevent infection in people at high risk of exposure during the period when scientists are still working on a vaccine.

“It’s controversial how useful antibodies would be in treating this kind of infectious disease,” Wilson said.

But using the antibodies to develop a rapid diagnostic tool could be almost as valuable. Currently, most hospitals use an antibody-based test to see if a patient has influenza, then they ship samples to state labs or the CDC for further testing, which usually takes several days. The new method of producing monoclonal antibodies would allow for faster and more widespread testing of new flu viruses as they emerge.

This may be the best expression I’ve seen yet of why swine flu still is a source of concern, even though it’s looking about as severe as normal influenza. From the Wall Street Journal’s coverage of a press conference today with Keiji Fukuda of the World Health Organization:

The reason why we’re paying so much attention to this virus is that the seasonal flu viruses have been around and circulating for many years. We understand their behavior and know most people have had previous infections and some immunity to them. When a new virus enters the human population and people do not have immunity to this virus, then the levels of serious illness and the levels of death can be higher than what we see with regular seasonal influenza.

…In the past, we’ve seen pandemics cause relatively fewer deaths, and some cause relatively huge amounts of death. One of them started out mild in the spring and over the course of several months became a severe illness. This is a situation in which things can evolve, and can do so quite differently. That’s why so much attention is being paid to what’s going on and why we’re jumping so hard on it. If it stays mild and people stay healthy, then that is great. But if it turns severe, then it’s something we have to know about, be prepared for and jump on.

Here’s Part 2 of our conversation with Kenneth Alexander, M.D., chief of pediatric infectious diseases. In this second and last installment, we discuss what ordinary people can do to avoid getting or spreading swine flu, some steps that medical professionals can take, and what would constitute a flu pandemic.

Here’s a video we shot yesterday of Kenneth Alexander, M.D., chief of pediatric infectious diseases, answering common questions about swine flu.

The news of unusual swine flu cases in Mexico and the American southwest has raised concerns that the outbreaks could herald a new flu pandemic - though the anxiety level in this AP story on today’s news seems just a bit too high at this stage. Something about the tone smacks of that movie “The Andromeda Strain” - “it’s something we’ve never seen before…”

It’s important to be vigilant, but overreaction also can have costs. In 1976, the CDC instituted an emergency immunization program in response to an outbreak of swine flu. The vaccine they used may or may not have been the cause of an uptick that year in cases of Guillain-Barre Syndrome (see this for an account of the 1976 experience by the former directors of the CDC and the immunization program).

President Obama has a history of interest in flu pandemic preparedness. He co-wrote a 2005 op-ed in the New York Times on pandemic measures, and later that year I interviewed him on that subject for the Chicago Tribune. You can see the transcript here. Two passages from that interview may offer clues about how Obama’s administration will handle the latest outbreak: 

Even when the SARS scare struck, the losses were in multiple billions of dollars. And that proved to be a false alarm essentially. If something like this genuinely occurred, you’d see global trade come to a standstill. And in addition to obviously the loss of life, the breakdown of our health systems, the economic consequences would be huge.

…you hate to be Chicken Little on this thing - no pun intended. But this is actually one of those situations where getting people a little scared, and certainly getting our government a little scared is probably a useful thing. And as I said, whatever investments we make are not going to be wasted, because the likelihood of pandemic is so high, even if it isn’t this particular pandemic. 

Perhaps Obama will see the issue differently as president than he did as a senator. But his instincts seem similar to those of the people who ran the 1976 immunization program - “When lives are at stake, it is better to err on the side of overreaction than underreaction.” If this outbreak continues, we may see another test of that idea.