3.0 Variant Profiles and Clinical Presentation
A clear understanding of the distinct and overlapping symptom profiles of the Nimbus and Stratus variants is crucial for accurate clinical triage, differential diagnosis, and effective patient management.
Cases linked to the Omicron lineages circulating in the 2024-2025 season typically manifest as an upper respiratory tract infection. The most common symptoms include:
- Nasal congestion or runny nose
- Cough
- Fatigue
- Fever or chills
- Head and muscle aches
- Sore throat
- Sneezing
- Shortness of breath
- Gastrointestinal symptoms (diarrhea, nausea/vomiting)
- Occasional loss of taste or smell
Nimbus (NB.1.8.1) Variant
The Nimbus variant has become a dominant lineage, reportedly responsible for approximately 43% of cases in the United States. Its clinical presentation is distinguished by two primary findings reported by UK National Health Service officials: a uniquely sharp sore throat, often described as a “razor-like” sensation, and swollen lymph nodes in the neck. In addition to these distinguishing features, Nimbus has been observed to cause gastrointestinal symptoms, including nausea, vomiting, and diarrhea.
Stratus (XFG) Variant
The Stratus variant has been identified as a spreading lineage in Europe and India. Its clinical profile is largely similar to other Omicron subvariants, though a notable observation is that it has been reported to cause hoarseness in some patients. Key reported symptoms include:
- Chills
- Shortness of breath
- Sore throat
- Fatigue
- Headache
- Nausea and vomiting
- Muscle aches
- Diarrhea
- Occasional loss of taste or smell
The significant overlap in symptoms between these new COVID-19 variants, influenza, and other common respiratory viruses presents a diagnostic challenge. Therefore, laboratory testing remains essential for a definitive diagnosis and appropriate public health action.