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expert reaction to reported developments in the winter flu outbreak

There is an ongoing outbreak of flu in the UK, which has resulted in hospitalisations and some deaths.


Dr Adam Kucharski, infectious disease modeller (specialising in influenza dynamics), London School of Hygiene & Tropical Medicine (LSHTM), said:

“The main strains currently circulating in the UK come from the influenza A/H3N2 and B/Yamagata groups of viruses. These are not completely new strains: the viruses are related to strains that circulated last year. However, flu viruses gradually evolve over time, changing their appearance so our immune system is less effective at recognising them. This is why people need to be vaccinated every year. Influenza A/H3N2 viruses have been circulating in one form or another since 1968 and the flu B/Yamagata group of viruses have been circulating around the globe since they emerged in 1988.

“The main factor that influences the size of an outbreak is the level of immunity against the current flu strains. If this year’s viruses are sufficiently different to strains that circulated in previous years – and to the strains covered by the vaccine – it can result in a larger outbreak.

“An epidemic is just a situation where the number of flu cases rises above a baseline level*, which is something that happens almost every winter. Influenza A/H3N2 viruses in particular have caused several large epidemics over the years.

“There are two main types of flu vaccine. The trivalent vaccine covers influenza A/H1N1, A/H3N2 and B/Victoria viruses. The quadrivalent vaccine covers all of these, plus B/Yamagata.”


Dr Peter Barlow, British Society for Immunology spokesperson, & Associate Professor of Immunology & Infection, Edinburgh Napier University, said:

“Influenza virus is not like the common cold virus – it causes an infection that can lead to serious illness, and even death.  Flu viruses constantly change, meaning that each year, scientists identify the flu strains in circulation and target the vaccine accordingly. Therefore it is incredibly important that people get vaccinated each year to protect against current circulating strains of the flu virus.

“We know each year that the influenza vaccine is not 100% effective but it is the best way we currently have of preventing the spread of this virus. It has been shown that the flu vaccine can significantly reduce the risk of a child dying from influenza infection.  We know that the more people that are vaccinated against flu, the less people will contract it.

“The flu vaccine offered this year does give a level of protection against a range of circulating flu strains.  It is free to people over 65, pregnant women and people with a long-term illness as well as healthcare workers and carers. Younger children are also eligible to receive the flu vaccine as a nasal spray.  The flu vaccine not only reduces the risk of catching the virus yourself, but also of spreading the infection to other people.

“You can also prevent the spread of the virus by regularly washing your hands often with warm water and soap.  This is also effective because the virus can survive outside of a person for 24 hours, and be spread by people touching contaminated surfaces.

“I would absolutely urge people to get vaccinated against flu today, as this can still help prevent the spread of the virus.” 

All our previous output on this subject can be seen at this weblink:

Declared interests

Dr Adam Kucharski: No conflicts of interest.

Dr Peter Barlow: “Dr Peter Barlow is funded by a grant from the Chief Scientist Office (Scotland) on a project investigating novel therapeutic approaches for respiratory viral infections.”

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