The 1918 flu killed more poor people than rich. The same affinity for inequity may be raising the 2013 flu's toll -- on the rich and poor alike.
Boston health officials have reported that low-income communities are bearing the brunt of the city's outbreak.
"What you see with flu activity is the same as what we see with health outcomes in general. Unfortunately, communities of color and low-income communities tend to share a disproportionate effect," Nick Martin, a spokesman for the Boston Public Health Commission, told The Huffington Post.
But as experts warn, such a disparity may not only be an issue of social justice. Elevated rates of the flu in poor communities may threaten the health of people who live in wealthier communities as well.
"We've found that getting lower-income neighborhoods covered with vaccines benefits higher-income neighborhoods," said Bruce Lee, an infectious disease expert at the University of Pittsburgh and lead researcher on a 2011 study of access to flu vaccines.
Based on computer simulations of 7 million "virtual people" in the Washington metropolitan area, Lee's team found the fewest infections at an epidemic's peak resulted when flu shots were allocated to the poorest counties. Delaying vaccinations in the poorest counties also increased infections among the wealthiest.
"This drives home the fact that we are all connected," Lee said.
Unfortunately, vaccine distribution still tends to go in the opposite direction. Los Angeles during the 2009 H1N1 pandemic is a case in point. One in every five South LA County residents received the flu shot, while two of every five residents of West LA County were vaccinated. South LA County includes many low-income communities; West LA County includes Malibu, Santa Monica and Beverly Hills.
Poor families, on average, are larger and live in more densely packed neighborhoods, Lee said, suggesting this gives the virus easy opportunities to spread. Poor communities may also have less access to health information, including a convincing rationale for getting a flu shot. And even for those motivated to get a shot, there are often additional roadblocks.
People living paycheck to paycheck may not have the money or insurance to cover a vaccine, for example. They may also lack the luxury of missing work to get a flu shot, or to rest through a bout with the bug. In addition to the germs shared with colleagues if they arrive at work coughing or sneezing, the commute itself can mean broad exposures, given their greater reliance on public transit and fewer options for working from home.
"If they're traveling all the way downtown to work," said Lee, "they can be quite active spreaders of disease."
Research in Europe makes a similar argument for prioritizing vaccines in low-income communities. Addressing social factors of infectious disease "is not purely an issue of solidarity and social justice," wrote the researchers, adding that elevated infectious disease rates in these populations "pose a health threat not only to them, but also to society at large."
They highlighted how high tuberculosis rates in prisons in the former Soviet Union "served as a reservoir that inoculated the overall resurgence of TB in the general population."
In Boston last weekend, officials set up 24 flu clinics offering free vaccines around the city. Martin of the public health commission said he hopes that the weekend push reached people who had previously been unable to afford a shot, or who couldn't take the time off from work during the week to seek one.
The commission declared a public health emergency last Wednesday and, along with health officials across the country, continues to urge people to get vaccinated. As The Huffington Post reported last week, only 37 percent of U.S. residents had been vaccinated as of the latest survey in late November.
Boston has recorded 750 confirmed cases of the flu so far this year, after only 70 such cases last year. Martin added that the city's flu season has yet to peak.
"We hope it peaks soon," he said. "And we hope our efforts to get people vaccinated this weekend will help to stem the outbreak."