Disease Fact Sheets

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The Snohomish County Health Department Communicable Disease Program investigates certain diseases to find the source of a disease or outbreak in order to stop any ongoing spread of illness.

Confirmed Disease

To ensure the health and safety of the community, when a contagious disease is confirmed in a place where people are in close contact (such as schools, daycares, and nursing homes), we follow up with the people who might be exposed to the disease as a result.

For example, parents may receive a parent letter and a fact sheet outlining what to watch for should you or your child become ill. For some diseases, we also make phone calls or send text messages to ensure you receive any necessary preventative treatment.


Thanks to vaccines, medical care, clean water, and safe food sources and handling, deadly diseases are more rare in Snohomish County than ever before. International travel and trade, however, mean contagious diseases are never far away. New diseases also pose a threat, as they can develop and spread rapidly.

Fact Sheets

Learn about common communicable diseases.

These fact sheets provide info about diseases and conditions, including how they spread, signs and symptoms, treatment, and prevention.

If you are looking for fact sheets focused on illnesses common in child care settings, please see the Fact Sheets for Child Care Providers page.