Detection of influenza C during an outbreak at an internal school, using a molecular tool; Havana, Cuba, September 2006

Influenza C virus usually causes a mild upper respiratory illness,1Katagiri S. Ohizumi A. Homma M. An outbreak of type C influenza in a children's home.J Infect Dis. 1983; 148: 51-56Crossref PubMed Scopus (77) Google Scholar but can also cause lower respiratory infections, such as bronchiolitis and pneumonia.2Moriuchi H. Katsushima N. Nishimura H. Nakamura K. Numazaki Y. Community-acquired influenza C virus infection in children.J Pediatr. 1991; 118: 235-238Abstract Full Text PDF PubMed Scopus (54) Google Scholar Seroepidemiological studies have revealed a wide distribution of influenza C virus throughout the world.3Joosting A.C. Head B. Bynoe M.L. Tyrrell D.A. Production of common colds in human volunteers by influenza C virus.Br Med J. 1968; 4: 153-154Crossref PubMed Scopus (29) Google Scholar, 4Matsuzaki Y. Sugawara K. Mizuta K. Tsuchiya E. Muraki Y. Hongo S. et al.Antigenic and genetic characterization of influenza C viruses which caused two outbreaks in Yamagata City, Japan, in 1996 and 1998.J Clin Microbiol. 2002; 40: 422-429Crossref PubMed Scopus (43) Google Scholar At the end of September 2006, the health authorities in Cuba detected an increase in acute respiratory infections at one internal school located in Arroyo Naranjo, a peripheral municipality of Havana City. In order to detect virus in nasopharyngeal swabs, a multiplex nested reverse transcription-polymerase chain reaction (RT-PCR) was employed that is able to detect respiratory syncytial virus (RSV) A, RSV B, adenovirus, influenza A virus, influenza B virus, and influenza C virus in clinical samples (previously described by Coiras et al. in 20035Coiras M.T. Perez-Brena P. Garcia M.L. Casas I. Simultaneous detection of influenza A, B, and C viruses, respiratory syncytial virus, and adenoviruses in clinical samples by multiplex reverse transcription nested-PCR assay.J Med Virol. 2003; 69: 132-144Crossref PubMed Scopus (213) Google Scholar). Primers encoding the nucleoprotein segment of influenza virus, the fusion protein of RSV, and the hexon gene of adenovirus were used. To avoid false negative results due to specimen inhibitors or extraction failure, an internal amplification control was included in the reaction mixture. The sensitivity achieved in this reaction ranged between 0.1 and 0.01 50% tissue culture infectious doses for influenza A and influenza B viruses, and between 1 and 10 molecules of cloned amplified products of influenza C virus, RSV A, RSV B, and adenovirus.5Coiras M.T. Perez-Brena P. Garcia M.L. Casas I. Simultaneous detection of influenza A, B, and C viruses, respiratory syncytial virus, and adenoviruses in clinical samples by multiplex reverse transcription nested-PCR assay.J Med Virol. 2003; 69: 132-144Crossref PubMed Scopus (213) Google Scholar Of the 16 samples tested, we obtained four positive for influenza C (25%). In individuals positive for influenza C virus, the predominant symptoms were arthralgia (75%), fever (75%), cough (50%), acute rhinorrhea (50%), and sore throat (50%); Table 1. We did not find evidence of any co-infections, however we did detect co-circulation with rhinovirus (13%) in two patients. This is the first report from Cuba of an influenza C outbreak causing respiratory symptoms.Table 1Clinical data for four patients with influenza C; Cuba, 2006PatientAge (years)GenderDays from onset of symptoms to sampling dateSigns and symptomsInfluenza C detection by multiplex nested RT-PCRCo-infections114M1Fever, cough+None detected215F3Fever, cough, headache, arthralgia+None detected338M1Fever, arthralgia, sore throat, rhinorrhea+None detected416F1Sore throat, arthralgia, rhinorrhea+None detectedRT-PCR, reverse transcription-polymerase chain reaction. Open table in a new tab RT-PCR, reverse transcription-polymerase chain reaction. During the influenza season particular attention is paid to influenza A and B virus isolates, as well as serology and molecular studies. However, during the winter, infection with influenza C virus may coincide with influenza A (H3N2 and H1N1) and influenza B virus activity.6Matsuzaki Y. Nakamura K. The virological, epidemiological and clinical features of influenza A, B and C viruses.Nippon Rinsho. 1997; 55: 2515-2520PubMed Google Scholar, 7Nakamura K. Sugawara K. Li Z.N. Influenza A, B and C viruses.Nippon Rinsho. 1999; 57: 301-304PubMed Google Scholar There have been several earlier reports of influenza C outbreaks occurring in closed environments such as military induction camps, hospitals, and children's homes.8Matsuzaki Y. Katsushima N. Nagai Y. Shoji M. Itagaki T. Sakamoto M. et al.Clinical features of influenza C virus infection in children.J Infect Dis. 2006; 193: 1229-1235Crossref PubMed Scopus (116) Google Scholar, 9Calvo C. Garcia-Garcia M.L. Centeno M. Perez-Brena P. Casas I. Influenza C virus infection in children, Spain.Emerg Infect Dis. 2006; 12: 1621-1622Crossref PubMed Scopus (18) Google Scholar People infected with influenza C virus may exhibit symptoms with a severity similar to that caused by influenza A and B virus infections. It is important to gain better understanding of the epidemiology of this virus with regular surveillance to determine its exact role in acute viral respiratory infections.10Greenbaum E. Morag A. Zakay-Rones Z. Isolation of influenza C virus during an outbreak of influenza A and B viruses.J Clin Microbiol. 1998; 36: 1441-1442PubMed Google Scholar Conflict of interest: No conflict of interest to declare.