An episode of CUSA3003 II

Another interesting scenario during CUSA3003 Biological Science Student Knowledge Enhancement Course was that we discussed about microbiology, where influenza caused by virus was briefly discussed.

From December 2017 to March 2018, Hong Kong was in the winter flu season, where influenza B predominated. In humans, there are three types of influenza viruses, they are namely, influenza A, B, and C. While the infection of influenza C is usually mild, influenza A and B can cause more severe respiratory symptoms, resulting in seasonal flu worldwide. Interestingly, the naming system between influenza A and B is different: for influenza A, common subtypes found in Hong Kong include H1N1 and H3N2 (‘H’ stands for a viral surface protein called haemagglutinin, that recognizes the target cell on the respiratory tract; ‘N’ stands for a viral enzyme called neuraminidase, which is responsible for releasing new viral particles out of the infected cells). However, for influenza B, we often simply call it ‘influenza B’, because we do not normally divide the virus into subtypes by ‘H’ and ‘N’. Owing to the differences of the naming system, we might notice that during the previous winter flu season in Hong Kong, ‘H1N1’ or ‘H3N2’ was not common in the news report; instead, we heard a lot of ‘influenza B’.

During the in-class discussion, I expressed my concern about the next seasonal flu in Summer, for instance, the winter seasonal flu in the United States (US) was caused mainly by influenza A H3N2, which was reported as quite serious. Some experts in the US warned that there could be a second wave of influenza in 2018 in their country, probably during the summer, based on the statistical data that an outbreak of influenza A was often followed by a wave of influenza B. To further complicate the issue, different types of influenza viruses had been affecting different regions in the world during the last winter flu season.

It could be extremely difficult to predict what will come next during the summer flu season in Hong Kong. Fortunately, the Centre for Health Protection conducts regular surveillance of the influenza in Hong Kong, where the data is openly accessible. Science Students interested in the topic of influenza can go through the statistical data and make their own analysis. Based on the latest data available today (3 August 2018), the overall influenza activity was low. The previous summer flu season caused by influenza A (H3N2) started as early as May 2017; whereas in the summer of 2014 and 2015, the summer flu season (also caused by H3N2) peaked at June and July. In 2018, so far the summer flu season this year has not yet arrived by the end of July 2018. This trend could be similar to that in 2016, where the summer outbreak (also by H3N2) was ‘delayed’ to autumn between September and October, which was followed by a relatively mild winter H3N2 outbreak between January and March 2017. In terms of the type of influenza, there are local and worldwide factors: locally speaking, H3N2 and H1N1 of influenza A, as well as influenza B can hit us again; from a global perspective, different types of influenza viruses can be imported from other regions, for example, H3N2 from the US or from the southern hemisphere, such as Australia; and H1N1 from the Southeast Asian and Eastern Mediterranean side can also spread to Hong Kong.

In the end, I think only scientific data will tell us the answer of the anticipated summer seasonal flu in Hong Kong; yet, there are many things we can do to protect our health: one of them is vaccination.

H1N1_influenza_virus
Influenza viral particles (Photo credit: wikipedia)

 

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