Differential Diagnosis for Viral Illness with Rash in Adults
- Single most likely diagnosis
- Varicella-zoster virus (chickenpox or shingles): This is a common viral illness that presents with a characteristic rash and is often seen in adults who have not been vaccinated or have weakened immune systems.
- Other Likely diagnoses
- Measles: Although vaccination has made measles less common, outbreaks can still occur, especially in areas with low vaccination rates, and it presents with a rash, fever, and respiratory symptoms.
- Rubella (German measles): Similar to measles, rubella is less common due to vaccination but can still occur, presenting with a rash, low-grade fever, and lymphadenopathy.
- Roseola: Caused by human herpesvirus 6 or 7, roseola is characterized by a high fever followed by a rash, typically in children but can also occur in adults.
- Enterovirus: Certain enteroviruses can cause rashes in adults, along with other symptoms like fever and gastrointestinal issues.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Monkeypox: A rare but potentially serious viral illness that presents with a rash, fever, and swollen lymph nodes, requiring prompt diagnosis and treatment.
- Smallpox: Although eradicated, the possibility of intentional release makes it a critical diagnosis not to miss, characterized by a distinctive rash and high mortality rate.
- Dengue fever: Transmitted by mosquitoes, dengue fever can present with a rash, severe flu-like symptoms, and potentially life-threatening complications like hemorrhagic fever.
- Rare diagnoses
- Hand, foot, and mouth disease: Typically seen in children, this enteroviral infection can occasionally affect adults, causing a distinctive rash on the hands, feet, and mouth, along with fever and sore throat.
- Fifth disease (erythema infectiosum): Caused by parvovirus B19, this illness is more common in children but can occur in adults, presenting with a "slapped cheek" rash and mild symptoms.
- Zika virus: While primarily known for its association with birth defects, Zika virus can cause a mild illness in adults with symptoms including a rash, fever, and conjunctivitis.