Flu season looks grim amid emergence of mutated H3N2 - report
Kyiv • UNN
UK health authorities are warning of a particularly severe flu season in the Northern Hemisphere. This is due to a new H3N2 strain that has several mutations and has already caused an early start to the flu season in the UK.
This year's flu season in the Northern Hemisphere appears to be particularly severe, warn UK health authorities, UNN writes, citing Ars Technica.
Details
The grim forecast is due to a new H3N2 strain that emerged in the summer (late in the Southern Hemisphere season) and has several mutations. These changes are not enough to trigger the most severe consequences – a deadly pandemic – but they could help the virus evade the immune response, leading to a huge number of severe illnesses that could place a significant burden on hospitals and clinics, the publication writes.
In the UK, the virus is gaining momentum. The flu season in the region started about five weeks earlier than usual. According to the latest data from the UK, H3N2 was responsible for more than 90% of cases where the flu virus type was analyzed.
"Of the two seasonal influenza A viruses, the currently dominant circulating virus (A/H3N2) typically causes more severe illness than A/H1N1, especially in older people," said Antonia Ho, an infectious disease expert at the University of Glasgow.
The early start to the flu season only exacerbates the situation, as not as many people get vaccinated early, Ho added. "As previous experience shows, flu waves that start early usually affect a larger number of people," she noted.
In the US, as indicated, key state data tracked by epidemiologist Caitlin Rivers show that flu activity across the country remains low overall. However, it is starting to pick up in the South and in individual states such as Hawaii, Arizona, and New York.
Vaccination
"Now is not the time to rush blindly into respiratory virus season," Danuta Skowronski, head of epidemiology for influenza and emerging respiratory pathogens at the British Columbia Centre for Disease Control and Prevention, told CIDRAP News.
Late last month, Skowronski and her colleagues published an analysis showing that the currently circulating H3N2 strain has accumulated enough new mutations (genetic changes) to become "mismatched" with the H3N2 strain used as the target for this year's flu vaccination.
"While mismatched vaccines may still provide protection, enhanced genetic, antigenic, and epidemiological (e.g., vaccine effectiveness) monitoring is necessary to assess risks and respond," Skowronski and her colleagues concluded.
Earlier this week, the UK Health Security Agency published a preliminary study that found that despite the mismatch, this year's vaccine still appears to provide important protection. The study showed that shortly after vaccination, the vaccine provided 70 to 75 percent protection against hospitalization in children aged 2 to 17 and 30 to 40 percent protection against hospitalization in adults. These levels of protection are within the typical range for flu vaccines, but they are more often seen at the end of the season, when vaccine protection has somewhat decreased, rather than at the beginning of the season, shortly after vaccination.
Nevertheless, officials called the results "encouraging." They noted the high rates among children, who, as parents can attest, have the ability to be "super-spreaders."
"The high effectiveness of the vaccine in children reinforces the need to vaccinate all eligible young people," said Jamie Lopez Bernal, a consultant epidemiologist for immunization at UKHSA. "The more children protected, the better for preventing the spread of flu."
"The bottom line is that we appear to be in for a very difficult flu season this year, and the best thing we can all do now to address this is to get vaccinated," said Adam Finn, professor of pediatrics at the University of Bristol.