In 19th century Ireland, a very significant portion of the population was solely dependent on the potato as its main source of nourishment. This mixed with milk were enough to keep the population sustained and nourished, as well as the potato being a cheap food, as many could plant potatoes on their own. So when the potato blight struck Ireland, many were now starving, looking for new foods. The biggest problem, Ireland didn’t grow much else when it came to food, and thanks to potatoes, domesticated animals were not as popular as the rest of Europe. This caused a nation wide famine, leading to terrible diseases like Measles, TB, and eventually cholera.
Many Irish decided to immigrate to the United States attempting to escape the famine of Ireland. This caused a huge influx In the population, mainly in New York City. This influx, along with the diseases many Irish contracted above, caused a problem in America, with many Americans getting sick. This led to the persecution of Irish Americans spreading diseases and being scapegoats for many diseases, i.e. Typhoid Mary.
An origin for the Irish Potato Famine lies in the potato leaves. These leaves have a strain of bacteria attached to it that was fatal to the potato crop. This bacterium, Phytophtora Infestans, completely disallowed growth of the potatoes, leading to the famine and disease ravaging the country of Ireland.