In looking through my postal librariana collection for my previous post related to New York Public Library branch librarians, I came across a postal card (circa late 1930s) used by NYPL to contact library users who had checked out books and a contagious disease in their home. Not too long ago a friend, knowing my interest in postal artifacts, called my attention to a blog post about disinfected mail. These two occurrences prompted me to take a look at the topic of library books and the potential spread of contagious diseases. As it turns out the discussion of this potential dates back to at least 1879 when W. F. Poole, Librarian of the Chicago Public Library, wrote about this topic in Library Journal. In 1891 at the ALA Conference in San Francisco a paper was presented by Gardner Maynard Jones, Librarian of the Salem Public Library (MA) titled "Contagious Diseases and Public Libraries". In their investigations both Poole and Jones found little evidence that contagious disease could be spread through library books. Jones, however, indicates that it is the responsibility of librarians to take reasonable precaution and to prohibit the circulation of books to houses with contagious disease. And further, that books returned from such houses should be disinfected or destroyed. This approach appears to have been adopted by a number of public libraries including the New York Public Library.
Bob Sink on his NYPL Librarians blog has expanded this story considerably as it relates to the New York Public Library.