To The Editors:
Echovirus type 33 (echovirus 33), the most recently discovered echovirus, has been associated with outbreaks of meningitis in school children in Germany,1 Canada,2 the Netherlands,3 Belgium4 and France.5 We know of only one reported outbreak of infection by this virus in an Asian country.6 That report described echovirus 33 infection in nine Japanese neonates, in July, 1994. It was believed to have been transmitted by an obstetric patient. Three of these nine affected neonates became seriously ill and one died of disseminated intravascular coagulation and renal failure. We now report the virtually simultaneous outbreak of echovirus 33 infection in four school age boys who lived about 400 km from the hospital where the outbreak occurred in the neonates.
The four school age boys were diagnosed as having aseptic meningitis between June and August, 1994 (Table 1). Symptoms included fever, headache, vomiting and stiff neck. Three of the four boys attended the same primary school, while the fourth lived near that school. All four were admitted to the Kiryu Kosei General Hospital. Marked increases in the lymphocyte count in the cerebrospinal fluid were seen in all cases. Treatment that included fluid replacement and the administration of antibiotics and nonsteroidal antiinflammatory drugs improved the conditions of the four patients, all of whom completely recovered.
To investigate the causative agent in these cases, the cell lines Vero, HEp-2, RD18s and HEL were used for viral propagation. Viral serotypes were then determined by using the neutralization method. The titer of the neutralization antibody against echovirus 33 was measured in paired samples obtained from these patients. Echovirus 33 was isolated from all four patients. In addition significantly elevated titers of neutralization antibody for echovirus 33 confirmed the diagnosis.
Our findings, together with the outbreak in neonates, verify that outbreaks of infection by echovirus 33 also occur in Japan. These data indicate that the disease caused by echovirus 33 is milder in older children than in neonates, as suggested by Modlin.7 These results illustrate the varied effects of echovirus 33 infection in pediatric age groups.
Hirokazu Kimura, B.S.
Hisanori Minakami, M.D.
Kenji Sakae, Ph.D.
Masae Ohbuchi, B.S.
Makoto Kuwashima, M.D.
Kunio Otsuki, M.D.
Gunma Prefectural Institute of Public Health; and Environmental Sciences; Maebashi (HK, MO, KO); Department of Obstetrics and Gynecology; Jichi Medical School; Tochigi (HM); Aichi Prefectural Institute of Public Health; Nagoya (KS); Kiryu Kosei General Hospital; Kiryu (MK); Japan
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