Covid cases surge in Singapore and Hong Kong: Key symptoms of LF.7 and NB.1.8 variants

COVID-19 cases are rising sharply across parts of Asia, particularly in Singapore and Hong Kong. The latest surge is being driven by two fast-spreading subvariants—LF.7 and NB.1.8—both of which are descendants of the JN.1 lineage, itself a subvariant of the Omicron strain.

The World Health Organization (WHO) has classified JN.1 as a “variant of interest” due to its rapid transmission, though it has not been labeled a “variant of concern.” Its descendants, LF.7 and NB.1.8, are now under global observation.

What’s driving the spike?The sharp increase in cases is primarily linked to increased transmissibility of these subvariants and waning immunity in the population.


According to Singapore’s Ministry of Health, “At present, LF.7 and NB.1.8 (both descendants of the JN.1 variant) are the main COVID-19 variants circulating in Singapore, together accounting for more than two-thirds of locally sequenced cases.”



This shift in variant dominance has led to a 28% rise in infections in Singapore during the week ending May 3, 2025. Similarly, Hong Kong has observed a significant increase in cases, with COVID-19 test positivity jumping from 6.21% to 13.66% over a four-week period, indicating rapid spread of these variants.


Experts say the rise is also influenced by reduced protection from prior infections or vaccinations, increased social mixing, and relaxed preventive behavior. Seasonal effects may also play a role in amplifying transmission during certain periods.


SymptomsSo far, the symptoms linked to LF.7 and NB.1.8 remain consistent with other Omicron subvariants. These include:

• Sore throat
  
  
  
• Mild cough
  
  
  
• Fatigue
  
  
  
• Fever
  
  
  

Health authorities across the region report that most cases remain mild, especially among vaccinated individuals. However, older adults and those with underlying health conditions remain more vulnerable to complications.

An official from India, which is currently monitoring 257 cases, noted: “As per the preliminary information available, the cases are mostly mild, not associated with unusual severity or mortality.”


As per Dr. Diksha Goyal, Senior Consultant at Internal Medicine Marengo Asia Hospitals Gurugram, the symptoms of LF.7 include- "fever, headache, body aches, fatigue, and occasionally gastrointestinal symptoms in the form of nausea or vomiting." Further, she added, "Respiratory symptoms of cough and dyspnea may be present in certain instances. The severity can also depend on the immunity and conditions of the patient."

"NB.1.8 will usually have mild to moderately severe respiratory symptoms such as sore throat, rhinitis, cough, and mild fever intermittently. Some will also present with fatigue, muscular aches, or a mild headache," said Dr Diksha. She also explained that while the symptoms are similar to a typical common cold but "can have variable severity by age, immunity, and comorbidities."
Vaccine protection and WHO classificationVaccines—particularly booster doses designed against Omicron—continue to offer strong protection against severe disease and death. However, preliminary data suggests LF.7 and NB.1.8 may partially reduce the efficacy of existing vaccines, leading to more breakthrough infections.



This has prompted health experts to consider updating vaccine formulations in the months ahead.

As of May 2025, the WHO has not classified LF.7 or NB.1.8 as Variants of Concern (VOC) or Variants of Interest (VOI). Instead, they are designated as Variants Under Monitoring (VUM). This status indicates that, while they do not currently pose a global health threat, they are being closely observed for their potential to affect transmission dynamics or vaccine effectiveness.


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