The flu season is here and death toll due to the flu has increased significantly this year in the United States. Read this news on CNN reporting 16 more children dead from flu, peak still to come.
One of the investigative posts by 
By doing some research in Pubmed, I found this very informative scientific paper in PLOS Pathogens published by Johnson et al. detailing 5 key facts about flu [1]. I would like to succinctly provide the main points of the paper here and if you have time, you can read the full paper yourself for the detail information by following the reference. It’s an open access paper and anybody can access and read it for free.
Influenza A and B are two main flu types that affects human during a flu season. These viruses mutate and replicate rapidly in response to the changing environments. Hence every year your flu vaccines need to predict the possible combinations of these new influenza variants that will outbreak in the flu season and accordingly formulate the vaccines with the cocktail of virus antigens that can provides broad protection against flu strains. For this reason, your flu vaccine is never 100% effective and wont provide you full protection. There is no way of accurately predicting which type of influenza mutants will be more abundant in this flu season.
To appreciate how flu transmits, adapts, and outbreaks, let’s get the 5 facts about flu straight as pointed out by the published paper.
1)How does flu evolves with time?
By making mistakes during replication process and reshuffling genes.
2) Who gets the flu?
Humans, birds, horses, pigs, and bats. Humans are more likely to get influenza B viruses because influenza B likes humans.
3) What gets around during influenza transmission?
Strains of flu that keep changing (mutating) with time. Yamagata and Victoria are influenza B virus lineages that have been co-circulating since 1983. Scientist normally review the epidemiological data and antigenic characteristics and responses of recent viruses in order to recommend the types of influenza strains to be included in a flu vaccine. This maximizes the protection against flu.
4) What’s worse than 1 virus?
A swarm of viruses. Influenza is more of a combination of genetically diverse viruses.
The paper reports
“It was observed that a genetic mix of viruses is transmitted to susceptible hosts, with minor variants tagging along with the dominant strain. It is thus feasible that while the influenza vaccine targets the dominant strain, minor variants continue to transmit, undergoing positive selection and becoming the dominant strain in subsequent transmissions.”
And this is the reason why flu vaccine is always not 100% effective, making flu little bit dangerous these days.
5)How much worse than 1 virus are 2 viruses?
2 viruses are more than two times worst than 1 virus. 2 viruses co-cooperatively facilitates their evolution and become more pathogenic by tricking our vaccine-boosted immune system. Viruses do things as a group and make us sick.
Reference:
- Johnson, Katherine EE, et al. "Getting the flu: 5 key facts about influenza virus evolution." PLoS pathogens 13.8 (2017): e1006450. https://doi.org/10.1371/journal.ppat.1006450