Case Definitions

Patient Under Investigation (PUI)

A patient under investigation (PUI) is a person with the following characteristics:

1. Fever (≥38°C, 100.4°F) and pneumonia or acute respiratory distress syndrome (based on clinical or radiological evidence) AND EITHER:
   • a history of travel from countries in or near the Arabian Peninsula¹ within 14 days before symptom onset, OR
   • close contact² with a symptomatic traveler who developed fever and acute respiratory illness (not necessarily pneumonia) within 14 days after traveling from countries in or near the Arabian Peninsula¹ OR
   • a member of a cluster of patients with severe acute respiratory illness (e.g. fever and pneumonia requiring hospitalization) of unknown etiology in which MERS-CoV is being evaluated, in consultation with state and local health departments.
   OR
2. Close contact² with a confirmed or probable case of MERS while the case was ill AND
   • fever (>100°F) or symptoms of respiratory illness within 14 days following the close contact. (This is a lower threshold than category A.)

PUIs should be evaluated in consultation with the state and local health departments. For more information, see CDC’s Interim Guidance for Health Professionals.

Confirmed Case

A confirmed case is a person with laboratory confirmation³ of MERS-CoV infection.

Probable Case

A probable case is a PUI with absent or inconclusive⁴ laboratory results for MERS-CoV infection who is a close contact² of a laboratory-confirmed MERS-CoV case.