In the late 19th century, as public libraries grew, so did anxieties about their threat to public health. Scarlet fever, smallpox and tuberculosis were thought to be spread through germ-ridden books, and various methods of disinfection were used, including steam, formaldehyde solution and heated carbolic crystals. (The practice was revived this year, in less elaborate form, as libraries began disinfecting books with antibacterial wipes.) Demands that libraries should be closed were resisted, but the 1907 Public Health Amendment Act threatened heavy fines for anyone infected with disease who borrowed books.