The 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: 

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

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.

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

Confirmed cases in Boston

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

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

Flu deaths this season in Minnesota, as of Thursday

Flu deaths so far in Massachusetts

Flu deaths so far in Pennsylvania

Children who have died from the flu this winter

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

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

Percent increase in flu vaccinations at CVS compared to last year

States that have reported widespread flu so far this winter

States in which flu outbreaks have been high to severe

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

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

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.

Flu fatality rate, in percent, in the 1918 pandemic

Fatality rate in the typical flu season

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

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