MILWAUKEE (CBS 58) -- People gathered at the Milwaukee County Zoo on Saturday, Aug. 29 for the annual Walk for P.I., an event hosted by the Immune Deficiency Foundation to raise awareness for primary immunodeficiencies.

The Milwaukee walk is one of six held nationally each year.

People with primary immunodeficiencies are missing part of their immune system or have one that doesn't function properly, leaving them vulnerable to illness and infection. Within the medical community, they're sometimes referred to as "zebras," a reference to the phrase taught in medical schools to focus on common diagnoses rather than rare ones.

A press release issued by the Immune Deficiency Foundation ahead of the walk mentioned 14-year-old Emmett Jamrok, who was diagnosed with a primary immunodeficiency disease after facing multiple life-threatening health struggles. Emmett's family says they connected with the Immune Deficiency Foundation for resources and community support and now hope to help educate others about the symptoms and challenges of the disease.

The event featured a 1-mile walk around the zoo followed by a festival.