:

Interactive map: Tracking the flu week by week

The Centers for Disease Control measures the level of flu-like illness in each state. This map shows the flu rates each week of the season, which lasts from October to April. To see how the virus spread, play the week-by-week timelapse below.

Flu level for week ending

► Play timelapse

Flu hospitalization rates

This index measures the number of flu-related hospitalizations per 100,000 people nationwide. The 2012-2013 season has passed 2009-2010 levels, when the H1N1 virus caused the first pandemic in 40 years.

What the flu virus looks like

How it works

big flu graphic

1. The genetic code for the flu is contained in eight strands of RNA. A protein on the virus binds to receptors on healthy cells in the airways and lungs, causing the virus to open and release its RNA.


2. The RNA moves to the cell nucleus, where it is incorporated in the cell’s machinery, directing the cell to make copies of the virus.


3. Another protein on the virus punches a hole in the cell, killing it and releasing the replicated virus.


4. The released virus either goes into the airway to find another cell to infect or it is ejected by a cough or sneeze and launched to find a new host.



Preventing the flu

Interrupting the virus

Vaccines teach the body’s immune system to make antibodies to kill the virus. A weakened form of the virus is grown in hens’ eggs, purified and killed with a chemical. Creating a new vaccine takes at least six months and requires hundreds of millions of eggs.

Drugs like Relenza and Tamiflu can stop the virus from budding out of the cell if administered soon after symptoms appear. Antivirals can also be given to people in contact with an infected person to prevent the disease from spreading.

SOURCE: CDC FluView Weekly Influenza Reports.
GRAPHIC: Darla Cameron, Dan Keating and Alberto Cuadra - The Washington Post.
Originally published Feb. 5, 2012. Data last updated .

More about flu season