1 Although any individual may develop a case of pinworms, the infection occurs most frequently in school children between 5 to 10 years of age.  Pinworm infections occur in all socioeconomic groups; however, human-to-human spread is favored by close, crowded living conditions. Spread among family members is common.
Before they start collecting, stamp collectors try to identify the types of stamps. These will help them segregate and sort stamps according to their classification. On its basic concept, there are three main classifications of stamps â special, commemorative, and definitive.
A standard book of stamps from the U.S. Postal Service contains 20 individual stamps. In January 2014, first-class postage rates increased to 49 cents for standard letters, making the cost of a book $9.80. A book of stamps can be purchased at any U.S. Post Office, or online at the USPS website. Several designs are available at no extra charge and include over 60 different themed stamps including holiday celebrations, historical events and people, and various other commemorations.