Laboratory and Epidemiology Commumications

SeroepidemiologlCal Study of Human Parechovims 1
Shinichi Takao*, Ydkie Shimazu, Shinji Fukuda, Masahiro Noda and Kazuo Miyazaki
Division ofMicrobiology II, HiflOShima Prefectural Institute of Health and Environment,
Minami‑machi 1‑6‑29, Minami‑ku, Hiroshima 734‑0007
Communicated by Hiroo lnouye(Accepted May 29, 2001)

Human parechovirus 1 (HPEVl), previously known astions. Neutralizing antibody liters were expressed as aechovirus 22, was recently reclassified as Parechovirus, areclprOCal of the highest semm dilution which inhibited thenew genus distinct from the Picornavirus genus on the basis

cytopathic effect by 50%. Titers exceeding 1 :4 were consid‑of its exceptional molecular and biological properties (1)･

ered to be positive.

HPEVI was orlglnally isolated in 1956 during an epidemic

Neutralizing antibody titers and the antibody‑positive rateof sumヮer diarrhea (2)･ PreviQus studies reported that theof age groups against HPEVl are shown in Fig. I. Significant

predomlnant Clinical manifestations Caused by HPEV 1 werelevels of antibody against HPEVI were fわund in almost all

infantile diarrhea and respiratory illness (3‑7), but more

the sera tested (178/195; 91%), with the titers rang.iTg fromserious symptoms such as myocarditis and encephalitis have

1 :4 to 1 :5 12 or more. The number orantibody‑posltlVe Sera

also been reported (3). Reports on infections and the epide‑

began to increase from 6 months of age, and then rapidly

miology of this virus, however, have been few, probably

increased further. Almost all the children aged between 1 andbecause infection with this virus is rare compared with other15 years old had antibody against HPEVl (1‑5 years old:

enteroviruses such as echoviruS 30 (8). In this study, we investi‑78%, 6‑10: 100%, 1 1‑15: 89%, respectively). Additionally,

gated the antibody prevalence orHPEVl in order to elucidate
the extent of its infection in Hiroshima Prefecture.

was higher than in other age groups (Fig.1). Similar

the geometric mean or neutralizing titers in these age groups

A total of 195 sera, collected in October 2000from residents

seroepidemiologlCal findings on HPEVl have been reported

living in Hiroshima Prefecture aged between 5 months andby others. ln a study in Finland, 72 of 79 individuals aged

79 years old, Were measured fわr neutralizing antibody titerover 1 year (9 1 %) had neutralizing antibodies against HPEV 1

Fgainst HPEV 1 ･ A recent isolate ofHPEV 1 (HAO0‑243 strain:lSOlated in Hiroshima Prefecture in July 2000) (9) was used(5), and studies ca汀ied out in the 1960s in Japan showed thatas an antlgen, and the method used was the standard micro‑HPEVl (6, 1 0). These results indicate that the seroconversion
for HPEVl antibodies occur in almost all children shortly
after I year of age. Furthermore, HPEVI was most commonly

almost all the chil血en aged over 1 year had antibody agalnSt

neutralizing technique f♭r enterovimses with some modi丘ca‑*Corresponding author: Fax: +81‑82‑254‑1908, E‑mail: takao

found in children aged under 1 year: according to the WHOdata from 1967 to 1974, 61% ofHPEVl infections reported@urban.ne.jp85Jpn. J. Infect. Dis., 54, 2001

Geometric mean tiEers o/seroposL'tives in dWerent age groupsiZE Ll% O) 034339

407

176

73112

8364

8376

1658

91

27

LO72339≧512

90 80 70 60 50 40 30 20 1 0t!13SJA!) SOd Rpoq!一ut!30 gt!)u3J

Jr3U Rpoq!)ut!ぎfZ!Tt!1一n3N

256

128
64

32

16

8

4

<465 10 15

1 ‑lーuJHL(Month)

Age

2025

30

35

40

45

50

55

60

65

7075

80

JrLリFig･ 1 ･ Age‑related distribution ofneutralizing antibody and antibody‑positive rate in age groups agalnSt HPEVl isolate.

Neutralizing antibody titer of I 95 sera collcctcd from residents of Hiroshima Prefecture in October 2000 were determinedusmg themicroplate technique. Sera were heated at 56oC for 30min before testlng. Two‑fold serial dilutionsfrom 1 :4 toI ‥512 0fthe sera were tested against apprやmately 100 TCID50 0fHPEVl (HAO0‑243 strain)･ Serum‑virus mixture wereincubated for 2 h at 370C before inoculation into 96‑welImicroplatc in which BGM cells were grown. The plates wereincubated in a CO2 incubator at 34oC for 4 days. Neutralizing antibody titers were expressed as a reclprOCal of the highest

serum dilution in which 50% protected the cytopathcic effect, and were plotted against age onthe graph. The percentages ofantibody‑positive sera (neutralizing titer of 1 :4 or more) were determined every 6 months (under 1 year of age) or every 5
years of age, and are shown as bars on the graph･ Geometric mean titers of each age group are shown onthe top of bars

corrcsponding tothe groups.

were seen in children under 1 year old, and 97% (566 out oftypes 22, 23 and 24 viruses. Arch. Gesamte Virusforsch.,

581 cases) Were observed in children aged under 15 years

1 1, 224‑247.

3･ Stanway, G･, Joki‑Korpela, P. and Hyypia, T. (2000):
Human parechoviruS‑biology and clinical significance.

(1 1)･ ln a retrospective study in Sweden, a total of 109 casesof HPEVl infection have been reported during a 25‑year

Rev. Med. Viro1., 10, 57‑69.
4･ Ehmst, A･ and Erikson, M. (1993): Epidemiologicalperiod from 1966 to 1990, and, ofall the patients from whom

HPEVI was isolated, 72% were aged under 1 year (4). Wealso previously reported that all of the patients from whomfeatures of type 22 echovirus infection. Scand. J. Infect.

HPEVI was isolated were under 2 years of age (9). Thus, weconsider that HPEVl is a common human pathogen whose

Dis., 25, 275‑281.
5･ Joki‑Korpela, P. and Hyypia, T. (1998): Diagnosis andepidemiology ofechoviruS 22 infTections. Clin. Infect. Dis.,

infection occurs in the early years of life.

We compared the neutralizing antibody titers or the sera

26, 129‑136.

against the recent isolate (HAO0‑243 strain) and the proto‑
type HPEVl (Harris strain, which wag isolated in 1959) (2)･

6･ Sato, N･, Sato, H., Kawana, 良. and Matumoto, M. (1972):

EcologlCal behavior of 6 coxsackie B and 29 ECHO
serotypes as revealed by serologlC Survey Of general

Antibody titers agalnSt the Ha汀is straln Were essentially thesame丘)r those orthe HAO0‑243 strain (ゐta not shown), which

population in Aomori, Japan. Jpn. ∫. Med. S°i. Bio1., 25,

suggests that the antlgenic epltOpe that induces the produc‑355‑368.

tion ofneutralizing antibody may be relatively well conseⅣed

7. Birenbaum, E., Handsher, R., Kuint, ∫., Dagan, R.,among HPEVl as described by Joki‑Korpela et al. (12). We

Raichman, 良., Mendelson, E. and Linder, N. (1997):

are cumntly plannlng a phylogenetic analysts among HPEV 1
to make clearthe molecular epidemiology ofHPEV 1 infection.

Echovirus type 22 Outbreak associated with gastro‑

intestinal disease in a neonatal intensive care unit. Am.
J. Perinato1., 14, 469‑473.

We thank Dr. Hiroyuki Shimizu of the National Institute

8. Yamashita, K., Miyamura, K., Yamadera, S., Kato, N.,
Akatsuka, M., Hashido, M., lnoue, S. and Yamazaki, S.

of Infectious Diseases, Tokyo, for providing Harris strain ofHPEVl.

( 1 994): Epidemics of aseptic meningitis due to echovims
30 in Japan. Jpn. ∫. Med. S°i. Bio1., 47, 221‑239.

9. Takao, S., Fukuda, S., Shimazu, Y, Noda, M. andREFERENCES

Tokumoto, S. (2000): The isolation of human parechovirusl･ Stanway, G. and Hyypia, T. (1999): Parechoviruses.

l from cases of acute resplratOry illnes in children. Jpn.

J. Viro1., 73, 5249‑5254.

J. Infect. Dis., 54, 36138.

2･ Wigand, R･ and Sabin, A. B. (1961): Properties of echo

10･ Nakao, T･ and Miura, 良. (1970): ECHO virus type2286

B, orC indicated in Fig. 1) 1 m above the floor. PointAwas
under an air‑supply vent in the center of the room, point B
was near an aiトeXhaust vent in a corner, and polnt C wasnear an air‑exhaust vent in the ceiling and su汀Ounded by an

incubator, a monitorlng equlpment unit, and a sink unit.

Thefluctuation in airbome particles in the NICU is shownin Fig. 2. At pointA, the particle number was 10 I 80/ft3 (4 ‑0:00

3:00

6:00

9:00

12:00

15:00

18:00

Time30 × 102/m3) which was the lowest level among the three moni‑Fig･ 2. Monitonng of airborne particles in an NICU. Airborne particlesof>1.0 LLm diameter were counted (averaged over lminperiods)*Co汀eSpOnding author: Fax: +8 1‑3‑3202‑7364, E‑mail: tkirikae

from 0:00 to 1 8:00. Each plot represents the average particle counts atintervals at point A, B, and C.

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