July 8, 2025, 1:04 pm | Read time: 4 minutes
In Germany, “Nimbus” is currently the most prevalent coronavirus variant by far. Meanwhile, in Southeast Asia and gradually in Europe, another cloud-named variant is gaining significance: “Stratus” (XFG). Indian doctors have noted frequent reports of hoarseness as a distinctive feature of XFG.
In the Southeast Asia region, a new coronavirus variant called XFG, or “Stratus,” is gaining momentum.1 The World Health Organization currently assesses the health risk from “Stratus” as low. Approved vaccines are expected to remain effective against severe illness. However, as the spread of “Stratus” increases globally and several Southeast Asian countries report a rise in new cases and hospitalizations, the WHO has classified it as a “variant under monitoring.”1 FITBOOK explains what doctors have reported about the symptoms so far and how the virus is currently spreading in Germany.
Overview
Common Symptom of “Stratus” – Reported by Doctors in India
XFG (“Stratus”) is a SARS-CoV-2 variant that has emerged from the LF.7 and LP.8.1.2 lineages. Despite the rapid spread of this variant, there is currently no evidence that “Stratus” causes more severe illness than other circulating variants.
In previous COVID-19 waves, loss of taste and smell were characteristic symptoms. For “Nimbus,” first detected in Germany at the end of March and currently responsible for 60 percent of COVID-19 infections according to the Robert Koch Institute, it was the “razor blade-like sore throat.”2 What are the specific symptoms of “Stratus”?
The WHO risk report contains no information on the symptoms of “Stratus” (XFG). Nor are there any official statements from national health authorities on specific symptoms of this new variant. However, various media sources, particularly from India, report observations from doctors. A notable feature of the current wave is the frequent reporting of hoarseness in COVID patients, as reported by the “Times of India” on May 30.3 Many patients this time are complaining of “dry or irritated cough, accompanied by sore throat and hoarseness.” Doctors from various hospitals have confirmed that hoarseness is now a common symptom in clinics across India. Hoarseness manifests as a scratchy or rough voice.
XFG – “Stratus” or “Frankenstein Variant”
Because “Stratus,” like the other currently globally dominant variant “Nimbus,” has the potential to trigger a COVID wave, the choice fell on another meteorological term for cloud types—”Stratus”—said virologist Dr. Ryan Gregory to the website Gavi.org.4 The organization Gavi is one of the world’s key players in vaccination programs. Virologist Gregory is part of a network of researchers that assigns unofficial nicknames to new virus variants.
“The Sun,” a British tabloid, refers to “Stratus” as the “Frankenstein Variant” because it resulted from the combination of two different COVID-19 strains.5 This occurs when a person is simultaneously infected with two different variants, which then merge into a new hybrid variant.
No More Severe Illnesses Than Other Variants
According to virologist Gregory, “Nimbus” and “Stratus” are currently competing for dominance worldwide. Despite their rapid spread, there is currently no evidence that “Stratus” (XFG) or “Nimbus” (NB.1.8.1) cause more severe illness than other circulating variants. According to “Gavi,” both variants have mutated spike proteins. This means they may be better able to evade immunity built up from previous infections or vaccinations. In other words, this likely makes it harder for the immune system to recognize and combat the virus.
How Rapidly Is “Stratus” Currently Spreading in Germany?
The spread of “Stratus” is still in its early stages in Europe, with the WHO reporting it at around 16 percent in the region. In England, the share of XFG rose from 10 percent in May to 40 percent by mid-June 2025. In Germany, “Stratus” last appeared in the Robert Koch Institute’s statistics on coronavirus variants in early June, with a percentage share of 5.56 percent; the week before, this share was 8.33 percent. The highest percentage recorded for “Stratus” (XFG) was in mid-May 2025. Currently, “Nimbus” dominates in Germany (60 percent). The situation is developing dynamically, so continuous monitoring remains important.
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Vaccine Effectiveness
Even though XFG has the highest relative growth advantage among the current lineages, the WHO currently sees no evidence of more severe illness or atypical clinical patterns. Approved vaccines continue to protect against symptomatic and severe cases, according to the risk paper on “Stratus.”