World Health Matters: Singapore: Could flu virus be wiped out?

by Gary Finnegan: One of the commonly circulating forms of the flu virus, which is particularly common among children, could be eliminated, according to researchers at the Duke-NUS Graduate Medical School Singapore.

An analysis of 10 years’ worth of data on human influenza B viruses has shed new light on the pathogen which can cause the seasonal flu. Findings from this study could help make flu immunisation programs more effective by better targeting vaccines. This has the potential, eventually, to eliminate one of the flu lineages completely.

Influenza epidemics cause an estimated three to five million cases of severe illness and 250,000 to 500,000 deaths every year. Four influenza virus lineages circulate in the human population where they cause seasonal epidemics. Of the four, two are influenza A and two are influenza B virus lineages, named Victoria and Yamagata.

Influenza type B tends to make fewer headlines than type A viruses because the former mutates less frequently. Type A viruses are more likely to be responsible for pandemics and their tendency for ‘antigenic drift’ increase the risk that annual flu vaccines will not match the flu viruses which circulate in any given year.

Nonetheless, type B flu viruses kill thousands of people every year and cause untold misery as well as placing a serious burden on health systems.

A new study, led by Assistant Professor Vijay Dhanasekaran and Associate Professor Gavin Smith, has presented the largest comparative analysis of human influenza B viruses ever undertaken. Results were achieved using advanced computational methodologies to analyse genomic data of the pathogen taken from human hosts. Significantly, this study is also the first to integrate demographic information such as the host’s age.

Findings offer new insight into the evolution and epidemiology of this highly infectious virus, and reveal how the two influenza B virus lineages fundamentally differ from each other and from the influenza A virus lineages.

“Our research shows that school aged children are more susceptible than adults to influenza B virus lineages, especially the Victoria lineage,” explained Asst Prof Dhanasekaran. “This younger population should be targeted for the use of the quadrivalent influenza vaccines.”

Commonly administered influenza vaccines are generally composed of two influenza A lineage viruses but only one influenza B lineage virus. Recently, quadrivalent influenza vaccines, which target all four lineages, have been approved for use. However, they are significantly more difficult to prepare, more expensive and have limited availability. This new study shows that it may be important to use these vaccines for a specific population.

The research team also ventures that a re-evaluation of influenza B vaccination strategies may have long term benefits in controlling the flu in the human population. Influenza B Yamagata viruses evolve at a much slower than influenza B Victoria viruses.

If the administration of the quadrivalent influenza vaccine were expanded sufficiently, it may be possible to eradicate the slower Yamagata lineage from humans. This would signify a major step towards triumph in influenza control and allow the return to an effective trivalent influenza vaccine, sometime in the future, which would target the remaining three flu virus lineages.