Pandemic! Cable 24/7 news coverage! Conflicting messages and confusing advice from Face the Nation to Facebook. The threat of influenza has been on everyone’s minds for the past month, but it has often been left to local schools and communities to make the practical, day-to-day decisions about containing H1 N1, a subtype of the Influenza A virus (aka “swine flu”). Science teachers are among those being asked important questions about viruses. A quick review might be in order.

Viruses are as old as cells—and perhaps older. A virus is basically a small segment of genetic material (DNA or RNA) wrapped in a protein coat or capsid. Influenza viruses have multiple strands of RNA as their genetic material (but are not retroviruses like HIV/AIDS). They only replicate in living systems, copying RNA to RNA.

Once a virus enters an organism (or comes in close proximity to a single celled organism), it recognizes and “docks” with a specific site (surface marker) on a specific type of cell membrane. Once attached, the virus’ genetic material enters the cell (normally through endocytosis.) There, the material becomes part of the genome of the host—either to reproduce more virus particles immediately or to remain dormant for some time until an environmental signal activates its metabolism.

Like all viruses, influenzas are extremely host specific, and have an uncanny ability to mutate quickly, changing their coat to confound immune systems. It’s the protein coat to which the immune system normally responds—and which vaccines target. Viruses are constantly hybridizing; two or more viruses in the same host might recombine, potentially resulting in a virus with the ability to infect a different organism or a different way. Virologists follow the mutations of the influenza virus around the world, and try to predict the upcoming threats for each “flu season” so the right vaccines can be available at the right time. Vaccine producers have been at work for months preparing a flu vaccine for the winter of 2009–2010 in the northern hemisphere.

But the best laid plans often go awry. A new virus identified first in Mexico and Southern California surprised epidemiologists. It was identified as A H1N1, “a subtype of INFLUENZA A VIRUS comprised of the surface proteins hemagglutinin 1 and neuraminidase 1.” Its virulence and the rapidity of its spread, first in Mexico, and then around the world, caused the frenzy in the media and serious concern among health officials. It was first dubbed “swine flu” because according to the Centers for Disease Control and Prevention (CDC) “laboratory testing showed that many of the genes in this new virus were very similar to influenza viruses that normally occur in pigs in North America. But further study has shown that this new virus is very different from what normally circulates in North American pigs. It has two genes from flu viruses that normally circulate in pigs in Europe and Asia and avian genes and human genes. Scientists call this a ’quadruple reassortant”’ virus.” While cases outside of Mexico have been generally less serious than the first reported cases inside that country, it was unclear why that was true.

Pandemic viral infections aren’t new. History has provided many examples:

• 1918. The Spanish flu pandemic, a variation of H1N1, started in 1918 and killed about 40 to 50 million people worldwide. (It followed the unprecedented movement of troops and populations during WWI and the Russian revolution.)
• A 1957 pandemic known as the Asian flu caused about 2 million deaths globally.
• In 1968, 1 million people died from the Hong Kong flu, a virus categorized as H3N2, relatively mild compared to others in the century.
• H1N1 re-emerged as “swine flu” in 1976.

The H1N1 subtype was responsible for the Spanish flu pandemic of 1918 and for swine flu in the early 1970s. Close, but not precisely the same! Each time a virus morphed into a new form, it has plagued populations until a “critical mass” of the population has developed immunity, then it has disappeared. When new mutations of the same general family of coat proteins emerge, even the immune systems of those who had another variation may not recognize them. The explanation for the start of each of these outbreaks is similar: the virus changed its coat.

“Major changes in the surface glycoproteins of influenza virus—called antigenic shift—lead to worldwide epidemics of influenza known as pandemics. There have been six instances of antigenic shift since 1889. In that year, H2N2 viruses circulated, followed by H3N8 in 1900, H1N1 in 1918, H2N2 in 1957, H3N2 in 1968, and H1N1 in 1977. Each pandemic strain carries HA and NA proteins that have been absent in humans for many years, and therefore immunity is either very low or nonexistent.” Spanish flu is now a footnote in the history books—probably because almost all of today’s humans have some resistance. The "swine flu" is a close relative. One eerie echo of that time though is being heard today: In the Spanish flu, young people were more susceptible to the disease and that’s recurring now. Young, healthy people are getting it more often than seniors.

Your students may bring to class reports from nonscientific media speculating on sinister origins for the new virus. That’s not logical or scientific. The biology is clear; viruses have been part of the biosphere for billions of years, and will continue to morph and change as long as there are hosts to help them do so. That makes it vital for both scientists and those who guide social activities to understand how to manage outbreaks and protect public health.

For epidemiology, the primary weapon is time. The spread of a new virus must be slowed. The only proven remedy for pandemic infection over the millennia has been time. Mexico’s actions illustrate the most effective approach—“social distancing.” For approximately three weeks, the government closed schools, prohibited large scale gatherings like sports and cultural events, and limited restaurants to take out. They reported a dramatic decrease in new cases as a result of these actions.

American school officials faced less direct guidance during the first few weeks of the outbreak. Perhaps because of the wide and diverse media coverage, the responses of local communities were often criticized. When isolated cases were verified, some schools closed for as long as three weeks, some for a few days, and some simply sent home warnings. Science teachers can help guide their systems by emphasizing principles to students that are valid not only this season but into the future:

• Recognize the symptoms of influenza: fever, cough, sore throat, fatigue, aches, and (often later) respiratory distress. These generally differ from the “common” cold by severity, fever and generalized body response.
• Encourage students to stay home at the first sign of symptoms. This is a difficult challenge in schools, because today’s parents often lack emergency child care options and resist keeping students home when symptoms are still minor. But that’s when influenza is most communicable, and when treatment is most effective.
• Remind students of the basic rules of hygiene: thorough hand washing, covering sneezes, proper disposal of soiled tissues. Every classroom should have the facilities for hand washing. (Remember that alcohol-based hand sanitizers are flammable. Hot water and antibacterial soap are the measures of choice in public places like classrooms.)
• When cases have been identified in populations that normally have close contact (like schools) social distancing is an appropriate management technique. Closing schools for a period that parallels the incubation period of the virus (approximately a week for H1N1) is a highly effective method to short-circuit a potentially epidemic outbreak. The U.S. Department of Health and Human Services has a thorough checklist for school district planning at www.pandemicflu.gov/plan/schoolchecklist.html, but in a letter to the CDC, Dr. Laura H. Kahn of Princeton indicates that some of these guidelines may still seem contradictory to school officials. (www.cdc.gov/eid/content/13/2/344.htm).
• Encourage the entire community to buy into the plan. Employers should encourage employees to stay home at first sign of illness, by providing sick days and support. Principals should use creative resources (like websites, teaching platforms, cable access, and voicemail systems) to provide homework and support for students who follow guidelines and protect the school community by staying home.

In order to make these measures work, everyone in the community must understand the rationale, the methods, and the potential benefits. That’s where science teaching comes in.

The best source for accurate public health information is the Centers for Disease Control and Prevention, www.cdc.gov/swineflu/swineflu_you.htm. CDC changed its guidelines for school closings on May 6. Check out the CDC website for the most current guidelines Students may also find the resources of PubMed (www.ncbi.nlm.nih.gov/sites/entrez?db=PubMed) to be particularly helpful to research specific influenza outbreaks and to put the current challenge in perspective. MedLine Plus (www.nlm.nih.gov/medlineplus/h1n1fluswineflu.html) has excellent consumer information on influenza as well. High school teachers and students can also participate in Science behind Swine Flu, a free online seminar hosted by the Darwin Facebook group and the Reading Odyssey on May 8. Scientists will answer questions about the medical and clinical aspects of the recent outbreak. For more information, go to www1.gotomeeting.com/register/598005577.