As many as 20 percent of Americans — 60 million people — are more vulnerable to foodborne illness due to their age or health conditions that affect their immune systems, according to a newly published study by British medical researchers.

In addition to the elderly, susceptible people include young children, pregnant women, alcoholics, diabetics and people stricken with AIDS, HIV, various cancers, multiple sclerosis and other diseases that affect their immune systems.

These are among the findings of a paper by British researchers Barbara M. Lund of the UK Institute of Food Research, and Sarah J. O’Brien of the University of Manchester, published in the journal Foodborne Pathogens and Disease.

Their study, compiling findings from scores more research papers in the U.S. and Europe, reconfirms what health officials have long understood — that some people are more vulnerable than others to foodborne bugs.  In most outbreaks of Salmonella, E. coli and other illnesses, a disproportionate number of reported victims are very young or very old.

The British study seeks to quantify that increased risk, and concludes that in the U.S., UK and other developed countries, between 15 percent and 20 percent of the population are more susceptible to foodborne pathogens.

For example, a French study of listeriosis concluded that people over age 65 were 7.5 times more likely to be sickened than otherwise-healthy people under 65.  Alcoholics were 18 times more likely to be sickened, diabetics were 30 times more likely, AIDS victims were 865 times more likely, and organ transplant patients were 2,500 times more likely to be sickened.

“Vulnerability arises often because of immune suppression, through either disease processes or the medications used to manage them, and at the extremes of age or in pregnancy,” the authors report.

The vulnerability means that fewer bacteria, especially foodborne or waterborne organisms, are needed to cause disease or increase the severity of the disease, they say.

For these groups, food safety is particularly important, they report. “Outbreaks of foodborne illness in vulnerable people in hospitals and other healthcare settings are avoidable and can be prevented in several ways.”

The key strategy is a diet of food that is less likely to carry pathogens. Their list of “higher risk” foods include:

— Raw or undercooked meat or poultry

— Raw, undercooked fish, or precooked seafood such as shrimp or crab

— Unpasteurized milk, or foods containing raw eggs (i.e. homemade eggnog)

— Raw sprouts, or unwashed vegetables

— Soft cheeses made from unpasteurized milk, such as feta, brie or queso fresco

— Hot dogs and luncheon meats that have not been reheated

— Unpasteurized, refrigerated pates or meat spreads

The authors also list low-risk foods, which include cooked meats and poultry, canned seafood, pasteurized milk and eggs, cooked sprouts, washed vegetables and hard, processed cheeses.