I suspect the answer you're looking for is that the government took steps to regulate the meat-packing industry.
Upton Sinclair's book, The Jungle, was published in February, 1906. In June of 1906, President Theodore Roosevelt signed into law The Food and Drugs Act, which began by describing its purpose as "an act for preventing the manufacture, sale, or transportation of adulterated or misbranded or poisonous or deleterious foods, drugs, medicines, and liquors, and for regulating traffic therein, and for other purposes."
There had been dozens of bills introduced in Congress since 1879 to impose regulations on the food production industry. The Jungle was not the only point of pressure calling for reforms. But Sinclair's book did serve as a final push to get necessary government regulations to be enacted.
