Experts in the UK are sounding the alarm over the rapid spread of a new mutated strain of H3N2 flu, already called one of the most dangerous in recent years. According to British media and scientists, the virus has mutated seven times over the summer, becoming "more aggressive", and the current seasonal vaccine, the composition of which was approved back in February, may not provide full protection against severe disease.
While the winter flu season is a seasonal phenomenon, the current surge in Britain has come earlier than usual. Official figures show that the rate of infection is already more than three times higher than the same period last year, with school-age children being hit hardest, with the sharpest increase in cases recorded among them.
NHS England chief executive Sir Jim Mackie has warned that this winter could "without a doubt" be one of the most difficult for the British healthcare system, with hospitals already stretched to the limit, waiting lists for elective treatment growing and patients forced to wait hours for help in emergency departments.
According to virologists, the key problem is the H3N2 strain, which has undergone seven genetic changes over the summer. These mutations have made it “hotter” and more “aggressive”, that is, capable of causing a more severe course, especially among elderly patients and people with chronic diseases. Professor Nicola Lewis, director of the Global Influenza Center at the Francis Crick Institute in London, emphasized in an interview with the BBC that H3 is traditionally considered a “hotter” and more “impactful” virus, and the current dynamics are atypical and cause her serious concern.
An additional risk is that the new H3N2 variant is significantly different from the strains that have circulated in the UK in recent years. This means that a significant proportion of the population does not have sufficient cross-immunity: the body simply does not “recognise” the virus, even if a person has had flu before or has been vaccinated in previous seasons.
The composition of the seasonal flu vaccine is traditionally determined in the winter - in February, so that manufacturers have time to produce millions of doses by the fall. However, the mutated variant H3N2 appeared only in June, so the current vaccine, according to experts, is not an ideal "antigenic hit" for this strain. Despite this, epidemiologists emphasize that vaccination remains critically important: the vaccine can significantly mitigate the course of the disease, reduce the risk of severe complications - such as pneumonia, sepsis or inflammation of the heart - and reduce the number of hospitalizations and deaths.
Symptoms of H3N2 flu are generally similar to other seasonal variants: a sudden high fever, severe muscle and joint pain, severe weakness and fatigue. However, doctors warn that the course can be more severe and recovery longer, especially in at-risk groups. In addition, there are signs that the new strain is spreading faster than usual.
Experts estimate that the basic reproduction rate (R) for flu in the UK is usually around 1.2 – meaning 100 people infected will pass the virus on to around 120 people. This season, preliminary estimates suggest an R of 1.4 – meaning the same 100 people could infect 140 people, significantly accelerating the growth of cases and putting pressure on the health system.
Ahead of a possible “explosion” of hospitalizations, British officials have already declared a de facto “vaccine alert” - doctors are urging everyone who is eligible to get vaccinated, especially the elderly, people at risk and children. According to them, even the partial protection provided by the current vaccine against new sub-strains could be a decisive factor in preventing thousands of unnecessary deaths this winter.
