A study by the agency found that pregnant women from ethnic backgrounds have made up a growing proportion of listeriosis cases in recent years.
The HPA suggests that established food safety messages may not be reaching, or may not be heeded by, all pregnant women, particularly those from ethnic minorities.
From 2001-8, there were 1,510 cases of listeriosis in England and Wales overall, with 181 in pregnant women.
In 2001, women from an ethnic background made up just a quarter of these cases, but by 2008 this had doubled to half of such cases. The overall number of cases per year has stayed relatively stable.
A second HPA study found that, for all patient groups, there were more cases of listeriosis in the most deprived areas of England compared to the most affluent. It suggests that deprivation is an important risk factor for listeriosis.