Covid-19 cases are once again on rise in the US and UK, fuelled by a new mutated ‘Stratus‘ or XFG variant, first detected in March. Now the dominant variant, it has taken over from NB.1.8.1, also known as the Nimbus variant, which was previously in circulation.
Covid-19 is evolving fast, becoming more infectious but milder with each variant. The virus that once sparked a global pandemic and caused widespread illness is still around, but now causes fewer hospitalisations. While lockdowns are a thing of the past, the virus may still impact people silently, with long Covid symptoms lasting for up to two years after infection, according to the Nature journal. The journey of Covid from 2020-2025 has been dramatic to say the least as the virus transformed from the deadly Delta to the much milder Omicron variants, thanks to vaccination and immunity from the past waves.
Covid in 2025
The virus, with its multiple mutations, has become better at infecting people and also evading immunity from past infections, but severe illness has become less of a concern. Vulnerable populations like the elderly, those with low immunity, or those with lung, heart disease, or diabetes, according to the World Health Organisation (WHO), are still at risk of developing complications.
“In 2025, Covid is milder, often resembling a cold or heat-related respiratory illness, with less drastic symptoms than in earlier years. Variants continue evolving, adding distinct features like hoarseness, razor-blade sore throat, or severe fatigue. Thanks to vaccination and immunity from past waves, severe illness and hospitalizations are significantly reduced—even as the virus circulates anew,” says Dr Tushar Tayal, Consultant, Internal Medicine, CK Birla Hospital, Gurugram.
“Covid-19 now looks like a bad cold or influenza, with symptoms such as extreme sore throat (or feeling of having a razor blade in the throat), cough, congestion, fatigue, headaches, and fever. Body aches and shortness of breath are the only other symptoms that may arise but severe pneumonia is not frequent, says Dr. Manav Manchanda, Director & Head – Respiratory, Critical Care & Sleep Medicine, Asian Hospital.
Dr Manchanda says Covid has come a long way from 2020, when it routinely caused respiratory collapse with a high fever, and when the loss of taste/smell was immense with hospitalizations of more than 20 percent in unvaccinated groups.
“Vaccination on a large scale, prior infections and Omicron-derived variants have lowered the severity, the mortality rate is currently down to below 1%, and severity lasts much shorter causing a 5-7lb average infection,” says the expert.
The symptoms of the latest variant Stratus range from fever, cough, fatigue, sore throat, to loss of taste and smell.
FinancialExpress.com spoke to experts on how Covid symptoms have changed over the past five years as the virus evolved into newer strains.
2025 (till mid-year)
“In 2025, symptoms of the Covid-19 disease are sore throat, cough, congestion or runny nose, fever or chills, fatigue, headaches, shortness of breath and occasional loss of taste/smell, but not that frequently as with previous strains. Nausea may be seen in some cases,” says Dr Manchanda.
Strains circulating in the US and India
In the US XFG (Stratus) and NB.1.8.1 (Nimbus) have become the dominant strains and trigger summer outbreaks with high transmissibility but reduced severity. In India, the NB.1.8.1 (also known as Nimbus), LF.7 and emerging XFG strains are common and lead to occasional upsurges despite a large proportion of the population having immunity. New modified vaccines against these variants have been recommended, adds the expert.
Stratus (XFG): Presents with fever, cough, fatigue, sore throat, loss of taste/smell, plus hoarseness; some patients report chest pain or difficulty staying awake.
Nimbus (NB.1.8.1): Known for the notorious ‘razor-blade’ sore throat, alongside typical symptoms like fever, cough, body aches, congestion; sometimes GI issues.
How Covid symptoms changed over the years
2020
In 2020, the Wuhan strain exhibited fever, dry cough, fatigue, and excessive loss of smell/taste, and marked lower-respiratory pathology, according to Dr Manchanda.
2021
The expert says, in 2021, Alpha/Beta to Delta variants were associated with similar symptoms but more severe oxygen deficiency and hospitalization; anosmia persisted.
2022
“Omicron 2022 (BA.1/2/5) took the patterns of sore throat, runny nose, headache, fatigue, decreasing smell loss, and milder disease,” says Dr Manchanda.
“Omicron and its subvariants arrived. The symptom profile shifted drastically toward cold-like signs, including headaches, sore throat, runny nose, sneezing, and fatigue. Loss of taste or smell and classic signs were less common. Also, night sweats began to be reported, especially with BA.5,” says Dr Tayal.
2023
In 2023, trend continued towards mild, non-specific, cold-like symptoms thanks to widespread immunity. Long-Covid incidence dropped compared to Delta era, as new sub-lineages appeared, but globally severity lessened, says Dr Tayal.
2024
“In 2024, the most common non-transmissible conditions were 2024 JN.1 that involved headaches, cough, and running nose,” says Dr Manchanda.
2025
“In 2025, KP.2/FLiRT, NB.1.8.1 (Nimbus), and XFG (Stratus) are predominant in the US and India, and include severe sore throat (razor blade), cough, congestion, largely mild upper-respiratory. Even high risk groups are not exempt to severity, he adds.