Web edition: June 29, 2012
Print edition: July 14, 2012; Vol.182 #1 (p. 30)
Redesigning flu mortality
In “Designer flu” (SN: 6/2/12, p. 20), researcher Michael Osterholmis quoted as saying that even if the actual kill rate of H5N1 is 20 times lower than the current estimate of 59 percent, H5N1 would still have a mortality rate that “far exceeds” that of the 1918 flu. Wikipedia gives a 1918 flu infection rate estimate of 27 percent, with 3 percent of the world’s population dying. Using the 3 percent mortality rate, “20 times lower” would require an assumption that the H5N1 infection rate is 100 percent, so the phrase “far exceeds” would require an infection rate of over 100 percent [for H5N1 to kill a larger percent of the world population], obviously impossible. Not that any of these numbers aren’t terrible and scary, but shouldn’t we avoid exaggerating the risk?
Linda Riley, Shawnee, Kan.
Mortality rates can be confusing. Osterholm was quoting the World Health Organization estimate that 59 percent of those infected with H5N1 die, which is different from the percent of the world population that dies. What’s more, estimates of the number of people killed by the 1918 flu vary widely, from 20 million to 100 million. If the estimates at the low end of that range are correct, then about 1 percent of the world’s population perished in the pandemic. If the H5N1 rate were a twentieth of the 59 percent estimate, or 2.95 percent, then H5N1 infection rates would need to be only about 50 percent to outstrip the total killed by the 1918 virus. Michael Osterholm’s larger point is that even if H5N1 is a far less deadly virus than WHO numbers suggest it is, if it were to become a pandemic it could kill millions more people than the 1918 Spanish flu did. — Tina Hesman Saey
Regarding Erin Wayman’s article “Egg wars” (SN: 6/2/12, p. 12), what is the explanation for egg color changing in two species of birds over a mere 40 years? My understanding is that change, or evolution, occurs as a result of random mutations in DNA over very long periods of time. The environment then determines the fitness of the mutation. So let’s say that you are getting random mutations frequently: What are the odds that the right mutation in egg color will happen within 40 years? Wouldn’t frequent mutations on this scale threaten the eggs with bad mutations?
Audrey Irvine, via e-mail
New mutations may not be necessary to explain the rapid changes in egg colors. Prinia eggs come in a variety of colors, such as white, blue, red and green. When a particular egg color is common in the prinias — say, blue — selection will favor cuckoo finches that lay blue eggs. But as blue mimic eggs become more common, selection may then favor prinia that lay eggs of rare colors, such as red. So the most common egg colors may change frequently, but the species isn’t necessarily evolving new egg colors—just switching back and forth among the colors they already produce. — Erin Wayman
Death of locked-up neutrons
Rebecca Cheung’s article “Secret of a lifetime” (SN: 5/19/12, p. 20) notes that “The Particle Data Group … currently puts the neutron lifetime at 881.5 seconds.” I assume this refers to free neutrons? Or do the neutrons in, say, an atom of iron disintegrate and get reconstituted about every 15 minutes? When I studied chemistry and physics long, long ago, nobody knew anything about that.
Ernest Nussbaum, Bethesda, Md.
The measurements mentioned in the article all refer to the lifetime of free neutrons. Generally, neutrons bound within atomic nuclei are stable. In some cases, these neutrons can live for billions of years, says Geoffrey Greene, a physicist at the University of Tennessee, Knoxville and Oak Ridge National Laboratory. Still, neutrons stored away in nuclei can die. For example, when carbon-14 radioactively decays into nitrogen-14, a neutron in the carbon atom becomes a proton, just like what happens at the end of a free neutron’s life. — Rebecca Cheung
Déjà vu on different scales
After seeing the glass squid on the cover of the June 16 Science News, I flipped open the magazine. My eyes first landed on the photo in the lower left of Page 16. It appeared to be a photomicrograph of some reddish bit of pond scum in a lovely, thin blue membrane, surrounded by a few dozen much smaller microorganisms. “What is that?” I thought. I was very surprised when I read what it was: Tycho’s supernova remnant. It is not excessively important that two things which differ in size by 20 orders of magnitude or more can look so similar. Nevertheless, that something viewed through a high-powered telescope looks so similar to something viewed through a low-powered microscope is a suggestion that some very different organizing forces in nature can result in similar-looking structures. Speaking unscientifically, this feels to me like some sort of fractal “déjà vu all over again.”
Jeff Barry, Acton, Mass.
Have microbiologists adopted a new naming code that I am not aware of? The publication of the name Candidatus Gloeomargarita lithophora in “Aquatic microbes have bony insides” (SN: 6/2/12, p. 14) makes no sense at all.
Norman Scott, Creston, Calif.