he frighteningly early and rapid spread of the flu across the U.S. this winter has been "pretty much unparalleled," as John Hick, an emergency physician in Minnesota, put it. Indeed, Boston — the epicenter of an outbreak in Massachusetts — declared a public health emergency this week. Many hospitals say they're overwhelmed with patients showing flu symptoms, and clinics across the country are running out of vaccine. And people might not take the flu as seriously as they should. Gregory Poland, professor of medicine and infectious disease at the Mayo Clinic in Rochester, Minn., tells USA Today that "we have this cultural thing in the U.S. about, 'Oh, it's just the flu.'" But the wave of illness could be quite deadly, and damage the economy, says Northwood University economist Timothy G. Nash, "if this is a major influenza outbreak, like the Spanish flu of 1918." Just how bad is this flu season? Here, a look, by the numbers: 

3,000
Low-end estimate of the annual U.S. death toll from influenza

49,000
High-end estimate of the annual U.S. flu death toll. The wide range shows how dramatically shifts in flu strains, early outbreaks, and other factors can affect public health.

1,500
People who have gone to the emergency room in Boston this winter complaining of flu-like symptoms

700
Confirmed cases in Boston

900
Percentage increase in the city's flu cases over last year

19,000
Flu cases confirmed in the state of New York so far this year, five times more than in all of 2012

27
Flu deaths this season in Minnesota, as of Thursday

18
Flu deaths so far in Massachusetts

22
Flu deaths so far in Pennsylvania

20
Children who have died from the flu this winter

25
Percentage absentee rate in Kiefer, Okla., schools — largely because of the flu

$4,000
High-end estimate of the medical expenses incurred by parents of flu-stricken children. The low end is $300. Moms and dads with sick kids may miss between 11 and 73 hours of work, depending on whether the child has to be admitted to a hospital.

3 million
Doses of flu vaccine the CVS drug store chain has administered so far this flu season

50
Percent increase in flu vaccinations at CVS compared to last year

41
States that have reported widespread flu so far this winter

29
States in which flu outbreaks have been high to severe

3
Adults over 65 for every 10,000 who have been hospitalized with the flu this winter

5.6
Percentage of people who have gone to the doctor with flu symptoms this season

2.2
Percentage who went last year

50 million
Deaths worldwide from the Spanish flu epidemic of 1918-1919, described in a report on the CDC website as the "mother" of all pandemics. Some estimates put the toll as high as 100 million.

2.5
Flu fatality rate, in percent, in the 1918 pandemic

0.1
Fatality rate in the typical flu season

$10 billion
Cost to employers from worker hospital and outpatient clinics in a typical flu season

0.5
Decrease expected in the 2.5 percent growth rate of the economy should this be the start of a major flu epidemic

Sources: CBS, CDC (2), Slate, Time, USA Today