Jpn. J. Infect. Dis., 53, 173-174, 2000

Laboratory and Epidemiology Communications

To see an article, click this [PDF] link.

Isolation of Influenza C Virus during the 1999/2000-Influenza Season in Hiroshima Prefecture, Japan

Shinichi Takao*, Yoko Matsuzaki1, Yukie Shimazu, Shinji Fukuda, Masahiro Noda and Shizuyo Tokumoto

Division of Microbiology II, Hiroshima Prefectural Institute of Health and Environment, Minami-machi 1-6-29, Minami-ku, Hiroshima 734-0007 and 1Department of Bacteriology, Yamagata University School of Medicine, Iida-Nishi 2-2-2, Yamagata 990-9585

Communicated by Hiroo Inouye

(Accepted August 16, 2000)




Although influenza C virus is considered to be an etiological agent for mild upper respiratory illness in humans (1), it can also cause lower respiratory tract infection (2). Seroepidemiological studies have revealed that the virus is prevalent worldwide and that infection occurs at an early stage in life (3,4). However, there is little information regarding its epidemiological and clinical features because the virus has only occasionally been isolated (2,5,6). According to the Infectious Agents Surveillance Report in Japan, while 5,699 influenza A(H1N1) virus isolates, 12,822 influenza A(H3N2) virus isolates and 5,232 influenza B virus isolates were reported in 1991-1996 in Japan, only 18 isolates of influenza C virus were reported during the same period (7). In this paper, we report eight isolated cases of influenza C virus from the 1999/2000-influenza season in Hiroshima Prefecture, Japan.

From November 1999 to March 2000, viruses were isolated from 257 of 667 clinical specimens (throat swabs and nasopharyngeal aspirates), most of which were collected from pediatric patients with acute respiratory illness in Hiroshima Prefecture. Of these, 158 were influenza A(H3N2) virus, 79 influenza A(H1N1) virus, 1 influenza B virus, 9 were adenoviruses of different serotypes, 5 were coxsackievirus type 4, 1 was herpes simplex virus type 1, and 8 (0.2%) were influenza C virus. As shown in Figure and Table, the cases of influenza C virus had no relationship in terms of their location or the time of collection, i.e., they were sporadic infections.

Viruses were isolated by using MDCK cells and/or 7-day-old embryonated hen's eggs (Table). In MDCK cells, the viruses produced only weak cytopathic effects sand grew very slowly. Several passages were necessary to attain a hemagglutination (HA) titer over 4 units/25 ƒÊl. Hemagglutination inhibition (HAI) and indirect immunofluorescence tests by using anti-C/Yamagata/8/89 resulted in the identification of eight influenza C virus isolates. The results were confirmed by RT-PCR assay using influenza C virus HA gene-specific primers (8). Among the eight isolates, seven were analyzed for antigenic characteristics with a set of monoclonal antibodies raised against hemagglutinin-esterase glycoproteins (9). It was found that the isolates could be divided into two antigenic groups: one similar to C/Yamagata/26/81 (9) that included C/H/290/99, C/H/247/2000, C/H/248/2000, and C/H/249/2000, and the other that included C/H/246/2000, C/H/250/2000, and C/H/251/2000. The data suggested that at least two antigenically different influenza C viruses circulated during the 1999/2000-influenza season in Hiroshima Prefecture. A similar phenomenon was reported from Yamagata City for the years 1988-1990 (9). As the virus may circulate throughout the year (2), we are currently investigating the occurrence of the virus in non-influenza seasons.

REFERENCES

  1. Katagiri, S., Ohizumi, A. and Homma, M. (1983): An outbreak of type C influenza in a children's home. J.Infect.Dis., 148, 51-56.
  2. Moriuchi, H., Katsushima, N., Nishimura, H., Nakamura, K. and Numazaki, Y. (1991): Community-acquired influenza C virus infection in children. J. Pediatr., 118, 235-238.
  3. Homma, M., Ohyama, S. and Katagiri, S. (1982): Age distribution of the antibody to type C influenza virus. Microbiol. Immunol., 26, 639-642.
  4. Chakraverty, P. (1978): Antigenic relationship between influenza C viruses. Arch. Virol., 58, 341-348.
  5. Ohyama, S., Adachi, K., Sugawara, K., Hongo, S., Nishimura, H., Kitame, F. and Nakamura, K. (1992): Antigenic and genetic analysis of eight influenza C strains isolated in various areas of Japan during 1985-9. Epidemiol. Infect., 108, 353-365.
  6. Chakraverty, P. and Matthews, R.S. (1994): Detection of influenza C virus in the United Kingdom. Eur.J.Clin.Microbiol.Infect.Dis., 13, 622-624.
  7. Editorial Committee of Infectious Agents Surveillance Report (1997): Isolation/detection of virus from human sources, by year, Japan,1991-1996. Jpn. J. Med. Sci. Biol., 50 (suppl.), S111-112.
  8. Zhang, W. and Evans, D.H. (1991): Detection and identification of human influenza virus by the polymerase chain reaction. J. Virol. Methods, 33, 165-189.
  9. Matsuzaki Y., Muraki, Y., Sugawara, K., Hongo, S., Nishimura, H., Kitame, F., Katsushima, N., Numazaki, Y. and Nakamura, K. (1994): Cocirculation of two distinct groups of influenza C virus in Yamagata City, Japan. Virology, 202, 796-802.

*Corresponding author: takao@urban.ne.jp

Go to JJID Homepage                        Go to JJID 53(4)
u