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)