CDC National Center for Infectious Diseases: Provides extensive information on a wide variety of infectious diseases and disease issues; the A to Z listing of diseases and program areas is an easy way to locate resources for particular diseases and topics.

CDC National Immunization Program: Information and answers to frequently asked questions about immunizations.

CDC Travel Information: Provides up-to-date information about immunization recommendations and current outbreaks for people planning international travel.

National Institute of Allergy and Infectious Diseases (NIAID): Presents information about many topics relating to allergies and infectious diseases; online publications cover topics such as asthma, autoimmune diseases, STDs, colds and flu, and Lyme disease. A detailed brochure called  Understanding the Immune System is also available.

World Health Organization: Health Topics: Provides information about many key infectious diseases and efforts to control them.

Alliance for the Prudent Use of Antibiotics: Provides information on antibiotics and their proper usage as well as tips for avoiding infections.

American Lung Association: Provides materials on a variety of lung diseases, including pneumonia, tuberculosis, influenza, and asthma.

Bugs in the News!: Provides information about microbiology—allergies, antibodies, antibiotics, mad cow disease, and more—in easy-to-understand language.

Cells Alive!: Includes micrographs of immune cells and pathogens at work.

Epidemic! The World of Infectious Diseases: An online exhibit from the American Museum of Natural History that provides information on the different types of pathogens and an extensive set of links.

Immunization Action Coalition: Promotes vaccination for children and adults; site includes extensive information about currently available immunizations (in many different languages).

Infectious Disease News: An online version of a publication focusing on infectious disease topics and trends.

National Foundation for Infectious Diseases: Provides information about a variety of diseases and disease issues.

National Jewish Medical and Research Center: Provides general information on respiratory, allergic, and immune system diseases, including asthma, tuberculosis, allergies, and autoimmune diseases.

University of Arizona Biology Project: Provides interactive resources for learning a variety of biology topics, including immunology and cell biology.

University of Wisconsin, Madison Campus: Institute for Molecular Virology: Provides resources relating to virology, including images of viruses, news and journal articles, and links.

Allergy and Asthma Network/Mothers of Asthmatics: Provides information and support for patients and their families, including materials on medications, products, and current research.

American Academy of Allergy, Asthma, and Immunology: Provides extensive consumer-oriented information and publications about allergies and asthma; the  National Allergy Bureau provides current pollen counts from stations throughout the United States.

American College of Allergy, Asthma, and Immunology: Provides information for patients and physicians, including an extensive glossary of terms related to allergies and asthma.

American Lung Association: Asthma: Provides information about asthma causes and management; includes a special section for kids with asthma.

Asthma and Allergy Foundation of America: Provides consumer-oriented educational materials about asthma and allergies.

Food Allergy Network: Provides information and online publications relating to food allergies.

Global Initiative for Asthma: Includes a directory of patient organizations and a pocket guide to the management of asthma.

Journal of the American Medical Association Asthma Center: Provides daily news summaries, patient information, expert advice, and glossaries.

MedicAlert: An emergency medical information service sometimes used by people with a severe allergy to food, medication, or insects. Members wear a bracelet or pendant that indicates a medical condition and provides a phone number for emergency medical personnel to obtain additional information.

National Heart, Lung, and Blood Institute (NHLBI): Asthma Information: Provides materials about asthma for the general public.

National Institute of Allergy and Infectious Diseases (NIAID): Publications: Provides many fact sheets and brochures on allergies and asthma.

American Autoimmune Related Diseases Association: Provides news and information about autoimmune disorders.

Arthritis Foundation: Provides resources and fact sheets for many types of arthritis, including rheumatoid arthritis and fibromyalgia. Educational materials, community service programs, and current research topics are highlighted.

Lupus Foundation of America: Provides information and advocacy relating to lupus, a common autoimmune disorder.

NIH National Institute of Arthritis and Musculoskeletal and Skin Diseases: Provides information on a number of immune system–related problems, including rheumatoid arthritis, lupus, and Lyme disease.

CDC NCID: New, Reemerging, and Drug-Resistant Infections: Includes information on a wide variety of issues and diseases as well as an online journal with articles on emerging infections and prevention issues

National Institute of Allergy and Infectious Diseases (NIAID): Emerging Infections: Provides information on research into controlling emerging infections.

World Health Day 1997: Emerging Infectious Diseases: Provides background information on emerging infectious diseases and fact sheets on reducing the risk of spreading disease.

World Health Organization: Communicable Disease Surveillance and Response: Provides information about emerging and tropical diseases, including current outbreaks; a WHO fact sheet on new and reemerging infectious diseases provides a general background to the problem and a list of recently recognized pathogens.

American Academy of Otolaryngology Head and Neck Surgery: Sinus Information: Provides information about sinus pain and sinus infections, including on online quiz to help determine whether symptoms are due to a cold, an allergy, or sinusitis.

Chronic Fatigue Syndrome (CFS) Home Page: Provides information about CFS, descriptions of current research into its causes, and links to support groups.

Hepatitis B Foundation: Provides materials about risk factors, prevention, symptoms, diagnosis, and treatment.

Hepatitis C: Provides extensive information about hepatitis C, including recommendations for testing.

Hepatitis Education Project: Includes links to sites with information about hepatitis and advice for setting up a local support groups.

Lyme Disease Foundation: Provides strategies for the prevention and treatment of Lyme disease and other tickborne infections.

Lyme Disease Network: Includes information about prevention and treatment, including photographs of ticks and the rash often associated with Lyme disease.

NIH National Institute of Dental Research/Insights on Human Health: Herpes: An overview of the different types of herpesviruses and their effects.