Influenza C Virus

Influenza C Virus was first isolated in 1947. Because this virus only rarely caused influenza, it has been seriously neglected by science. Influenza C Virus is known to infect humans, pigs and dogs. Influenza C virus is unique since it contains only one spike protein, the hemagglutinin-esterase-fusion glycoprotein HEF that possesses receptor binding, receptor destroying and membrane fusion activities, thus combining the functions of Hemagglutinin (HA) and Neuraminidase (NA) of influenza A and B viruses.

Recently, scientists finally investigated all known isolates from Influenza C Virus[1]. The results showed that there are six distinct lineages, named C/Taylor, C/Mississippi, C/Aichi, C/Yamagata, C/Kanagawa, and C/Sao Paulo.

They contain both antigenic and genetic lineages of the hemagglutinin-esterase (HE) gene, and the internal genes PB2, PB1, P3, NP, M, and NS are divided into two major lineages, a C/Mississippi/80-related lineage and a C/Yamagata/81-related lineage.

Since 1947, reassortment events were found over the entire period. Several outbreaks of Influenza C Virus between 1990 and 2014 in Japan consisted of reassortant viruses, suggesting that the genomic constellation is related to Influenza C Virus epidemics. The results from another study suggest that epidemics of influenza C virus infection periodically occur and the replacement of the dominant antigenic group may be caused by immune selection within older children and/or adults in the community[2].

The results indicate that reassortment is an important factor that increases the genetic diversity of influenza C virus, resulting in its ability to prevail in humans.

My concern is that Influenza C Virus will unknowingly change so much that it suddenly turns into a deadly variant.

[1] Matsuzaki et al: Genetic Lineage and Reassortment of Influenza C Viruses Circulating between 1947 and 2014 in Journal of Virology – 2016
[2] Matsuzaki et al: Epidemiological information regarding the periodic epidemics of influenza C virus in Japan (1996–2013) and the seroprevalence of antibodies to different antigenic groups in Journal of Clinical Virology – 2014