NEW YORK – This year’s flu season is off to a quick start and so far it seems to be dominated by a nasty bug.

Health officials say the flu vaccine seems well matched to the viruses making people sick, but it’s too early to tell how bad this season will be. The main flu bug this season tends to cause more deaths and hospitalizations, and vaccines tend not to work as well against this type.

Flu began picking up last month. By the end of last week, seven states reported widespread flu activity: Arkansas, Georgia, Louisiana, Massachusetts, Mississippi, Oklahoma and Virginia.

Most flu seasons don’t really get going until around Christmas. That’s how last year’s flu season played out.

The Centers for Disease Control and Prevention reported the latest data Friday.

Is the flu near you? Check our Maine counties map

The flu season runs from October into May. It isn’t clear why flu is seasonal. It is probably a combination of cold weather forcing people into close proximity indoors and cold dry air which seems to make transmission of the virus easier and also to prevent humans from fighting off the flu.

Hover over the map for detailed county-by-county statistics, or compare week-by-week numbers by hovering over each week’s bar in the bar chart.

This interactive was updated on November 30, 2017 to include the most recent data from the previous week.