After the liberation of Poland from the German occupation, our country, just like after the First World War, found itself in a very difficult position. The poor health and economic situation was aggravated by the limited freedom of action related to the occupation of the country by the Soviet army and the movement of people caused by the change of Poland’s borders. Large epidemics of typhus, typhoid fever, pseudo typhoid, diphtheria, tuberculosis, syphilis and other diseases have exploded. The National Institute of Hygiene for the second time in its history took part in the fight against epidemics throughout the country.

PZH resumed its activity in March 1945, initially having its headquarters in Łódź. At that time, the PZH buildings in Warsaw were being renovated, devastated and partially burned as a result of hostilities. The transfer to Warsaw took place in 1947. Under the direction of PZH, former regional branches resumed operations. In addition to the existing ones, new branches of PZH were organized in Szczecin, Wrocław, Gdańsk, Białystok and Rzeszów.