Epidemic Myalgia in Adults Associated with Human Parechovirus Type 3 Infection, Yamagata, Japan, 2008

Katsumi Mizuta

, Makoto Kuroda, Masayuki Kurimura, Yoshikazu Yahata, Tsuyoshi Sekizuka, Yoko Aoki, Tatsuya Ikeda, Chieko Abiko, Masahiro Noda, Hirokazu Kimura, Tetsuya Mizutani¹, Takeo Kato, Toru Kawanami, and Tadayuki Ahiko

Author affiliations: Yamagata Prefectural Institute of Public Health, Yamagata, Japan (K. Mizuta, Y. Aoki, T. Ikeda, C. Abiko, T. Ahiko); National Institute of Infectious Diseases, Tokyo, Japan (M. Kuroda, T. Sekizuka, M. Noda, H. Kimura, T. Mizutani); Yonezawa City Hospital, Yamagata (M. Kurimura, Y. Yahata); and Yamagata University Faculty of Medicine, Yamagata (T. Kato, T. Kawanami)

Abstract

Human parechovirus has rarely been shown to cause clinical disease in adults. During June–August 2008, a total of 22 adults sought treatment at Yonezawa City Hospital in Yamagata, Japan, for muscle pain and weakness of all limbs; most also had fever and sore throat. All patients received a clinical diagnosis of epidemic myalgia; clinical laboratory findings suggested an acute inflammatory process. Laboratory confirmation of infection with human parechovirus type 3 (HPeV3) was made for 14 patients; we isolated HPeV3 from 7 patients, detected HPeV3 genome in 11, and observed serologic confirmation of infection in 11. Although HPeV3 is typically associated with disease in young children, our results suggest that this outbreak of myalgia among adults was associated with HPeV3 infection. Clinical consideration should be given to HPeV3 not only in young children but also in adults when an outbreak occurs in the community.

Human parechovirus (HPeV) is a positive-sense, single-stranded RNA virus belonging to the family Picornaviridae and the genus Parechovirus (1,2). HPeV type 1 (HPeV1) and HPeV2 were discovered in the United States in children with diarrhea in 1956; initially designated echovirus types 22 and 23, respectively, these viruses were recently reclassified and renamed (1,2). In 1999, HPeV3 was identified from a 1-year-old child with transient paralysis, fever, and diarrhea in Japan (3). Complete genome sequences are available for HPeV1–8, and viral protein (VP) 1 coding region sequences have recently been reported for HPeV9–16 (1,4).
HPeV1 and HPeV2 mainly cause mild gastrointestinal or respiratory illness, but more serious diseases have been occasionally reported, including myocarditis, encephalitis, pneumonia, meningitis, flaccid paralysis, Reye syndrome, and fatal neonatal infection (2,5,6). HPeV3 also causes not only mild gastrointestinal and respiratory tract illness but also severe illness in young children, including sepsis and conditions involving the central nervous system (1,5,7–13).
Although the seroprevalence of the recently discovered HPeV4–8 are unknown, HPeV1–3 infections usually occur in early infancy (1,3). Because all children have antibodies against HPeV1 after 1 year of age, HPeV1 seroconversion during the early months of life has been clearly established (2). HPeV3 is reported to infect younger children more often than HPeV1; HPeV3 infections occur most commonly among infants <3 age="age" href="http://wwwnc.cdc.gov/eid/article/18/11/11-1570_article.htm#r1" months="months" of="of" title="1">1

,10,11). In contrast, reports in the literature that describe HPeV3 infection in persons >10 years of age are rare (1,14). An unusual outbreak of epidemic myalgia among adults occurred during June–August 2008 in Yonezawa, Yamagata, Japan, and epidemiologic investigation found that it was associated with HPeV3 infection. We describe this outbreak and provide expanded information about the clinical spectrum of HPeV3 infection.