1. Department of Virology, Institute of Tropical Medicine; Nagasaki University; Nagasaki Nagasaki 852 Japan
2. Department of Neurology; Nihon University Medical School; Bunkyo-ku Tokyo 113 Japan
3. Department of Neurology, Dow Medical College; Civil Hospital; Karachi Pakistan
4. Department of Pediatrics, Dow Medical College; Civil Hospital; Karachi Pakistan
5. Department of Biochemistry, Faculty of Human Sciences; Aga Khan University; Karachi Pakistan