Strains of seasonal influenza behave differently from season to season, strain to strain. And these differences are quite telling.
Epidemiologists at the Centers for Disease Control and Prevention (CDC) study patterns of flu data from the current season against historic data from flu seasons past. The comparison helps inform their decisions: what kind of vaccines are needed, how and where should they be distributed?
One day, as data sets improve, scientists will be able to predict how future strains of seasonal flu will spread.
The above infographic was created for Popular Science by Pitch Interactive – using numbers from the CDC and Google Flu Trends.
And here are some highlights:
- Seasonal flu usually arrives in 2 waves: a small peak in mid-December followed by a doubling in the rate of transmission that spikes in early February. High incident rates early in the season hint at particularly contagious strains.
- One glaring exception is the purple curve: the 2009 H1N1 pandemic caused a spike in mid-October. By midwinter, the flu was in rapid decline thanks to vaccine distribution and an already high exposure rate.
- And then there’s the brown curve: in 2003, the CDC synthesized a vaccine for an older strain that ended up being less virulent than another, leading to more cases. (In a given season, there are about 3 flu strains.)
- On the sidebar to the right: the lighter colors are data from the CDC’s Epidemiology and Prevention Branch of the Influenza Division. To come up with a percentage of flu-related doctor and ER visits every week, they aggregate data from 3,000 doctors’ offices, 140 labs, 3,000 outpatient healthcare providers, vital statistics offices in 122 cities, and epidemiologists at health departments in every state.
- Compare that to the darker colors representing Google Flu Trends, which computes the rate of infection in a population by tracking search terms like “sore throat” and “cold chills.”
- The rate of transmission of the 1918 pandemic that killed 40 million people closely mirrors the data from the 2009 H1N1 pandemic. In fact, the 2 strains are closely related.
From Popular Science.
This post was originally published on Smartplanet.com