Isolation of influenza virus type A/H3 in nonepidemic season, August 2000 - Aichi
(IASR 2000; 21: 268-268)

Two sporadic cases of influenza A/H3 were found in a nonepidemic season (August).

The cases were 10 months old twin sisters. The elder girl presented with fever and intermittent convulsions and was hospitalized in Toyohashi Municipal Hospital on August 4, 2000. Because of high fever, her younger sister was admitted on the following day, too. Two pharyngeal swab specimens were collected on August 7 and 8, and were inoculated on MDCK cells. Cytopathic effect was observed.

Hemagglutination inhibition (HI) test using turkey red blood cells and ferret antisera provided by NIID revealed that the 2 strains had a high HI titer (640) for A/Sydney/5/97. But the amino acid sequence resembled to that of A/Panama/2007/99, rather than to those of the A/Sydney strain or strains isolated in Aichi Prefecture in the 1999/2000 season. The nucleic acid sequence of the hemagglutinin gene was identical between the 2 isolates.

Family history found that their brother going to kindergarten had presented with common cold-like symptoms, but other family members did not. All family members and relatives did not have an episode of recent international travel. Travel history of kindergarteners and the staff remain to be seen. Although epidemiological investigation is needed more, the brother was suspected as the index case.

The elder sister was diagnosed as acute encephalopathy, as computed tomography demonstrated mild brain edema and the elevation of cell counts was not found in the cerebrospinal fluid. She recovered completely after intensive treatment. The younger girl developed fever and cough only and the illness was self-limited.

Since the third week of September 2000, several influenza A cases that showed a positive result with rapid diagnosis kits have been reported in Aichi Prefecture.

Reported by: Katsuhiko Sato, Takayuki Morishita, Miyabi Sugiyama, Teruo Yamashita, Kenji Sakae, Dept. of Microbiology, Aichi Prefectural Institute of Public Health; Rika Nagasaki, Mikinao Obayashi, Section of Pediatrics, Toyohashi Municipal Hospital

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