Figure 2 is a histogram showing the number of stools that tested positive for Salmonella each month between 2010 and 2014, by type of test performed. The types of test include polymerase chain reaction, culture, or both polymerase chain reaction and culture. A line shows the total percent positivity for Salmonella. Prior to late 2013, all specimens were positive by culture alone. After polymerase chain reaction was introduced in late 2013, the total number of tests positive and percent positivity increased, and approximately one fifth of specimens were positive only by polymerase chain reaction and two fifths were positive by each of culture alone or culture and polymerase chain reaction together.