Infectious Disease Sureillance Center

IDWRNovel Influenza A(H1N1) (21 May 2009)

Interim report on clinical presentation of the novel influenza A (H1N1) cases reported from Kobe City

May 19, 2009

National Institute of Infectious Diseases
Kobe Institute of Health


On 16th May, 2009, three cases of the novel influenza A (H1N1) virus infection were reported from Kobe City, Hyogo, Japan. More cases have been reported from north and west part of Hyogo prefecture, and nearby prefecture (Osaka) following to the first report.
As of 1:00 a.m. (JST), 19th May 2009, a total of 163 cases with laboratory confirmation have been reported nationally.
The following report covers 43 cases up to 19th May, confirmed in Kobe City and hospitalized or followed up by outpatient clinic in order to provide information on clinical presentation of infection for the use of diagnosis and treatment at front line hospitals.

According to the Infection Control Law, new type influenza is categorized as Group 2 currently which orders the case to hospitalize and treated. Because of the law requirements, Kobe City requested hospitalization for all cases. The sample group of this report is also legally hospitalized cases. However, the rapid increase of the number of cases beyond the beds availability with the fact most were mild cases lead Kobe City and Osaka prefecture to revise policy of the hospitalization based on the clinical indication.

We would like to forward our gratitude to the members and staffs of Kobe City Medical Center General Hospital, Nishi Kobe Medical Center for their cooperation.

Clinical information

<Case description and underlining conditions>
Forty-three cases were investigated.  The median age was 17 (range 5 to 44) and the majority was teenagers. Female to male ration was 1.3 (24 female, 19 male).  Thirty one cases had underlying condition such as chronic bronchial asthma (6 cases, 15.8%). No cases had diabetes mellitus, cardiac diseases, immunosuppressive condition, or malignant tumor.  None of 24 female cases had possibility of pregnancy.

<History of seasonal influenza vaccination and influenza infection during 2008/2009 season>
Pre-seasonal vaccination coverage of 2008/2009 season on 42 cases was 52.4% (22 cases). Cases experienced influenza infection during 2008/2009 season was 7.5% (3 cases out of 40).

<Rapid kit test for influenza>
Rapid kit test was performed on all 43 RT-PCR positive cases as screening. The test was performed on the sample taken on Day 0 to 4 (median Day 1) from the date of onset.Twenty three cases (53.5%) were positive as type A influenza by the test. On the other hand, 20 cases (46.5%) those confirmed later by PCR were type A negative by the rapid test.Sampling at the early stage of disease course might be the cause of this high negative rate. The type of the kit used at each hospital was not investigated.

<Clinical feature on admission>
High fever was observed in about 90% of 43 cases. Symptoms reported around 60-80% frequency included fatigue, feverish, cough and sore throat. Nasal discharge, nasal congestion and headache were observed in about a half of cases. Gastroenteric symptoms like vomit and diarrhea was reported around 10%, and conjunctivitis for 7%. No neurological symptom was reported.

<Laboratory data on admission>
The laboratory data from 20 cases was available on admission. 
White blood cell count was 3200-11400 /mm3 (median 5100)
CRP 0.1-9.2 mg/dl  (median 1.3)
Liver enzyme data was available for 7 people.
GOT 13-64 IU/dl (median 20)
GPT 7-168 IU/dl (median 13)

No chest X-ray was taken since pneumonia was not suspected by physical examinations.

<Treatment course>
Antiviral treatment by oseltamivir was given to 19 and by zanamivir inhalation to 20 out of 43 cases.  Age breakdown for the treatment selection is as follows.
One case under 9 was treated by oseltamivir.
Thirteen cases (36.1%) of 36 teenagers were treated by oseltamivir and remained 20 cases (55.6%) were treated by zanamivir. There were 3 cases with no medication (8.3%) among teenagers.
Five out of 6 cases above the age of 20 were treated by oseltamivir. Though the reason was not clear, one case above the age 20 was given no medication. This case was diagnosed in Day 3 of illness.
Date past before treatment was one day in median, ranging from zero to 4 days. Antibacterial treatment was given to 2 of the cases.

<Indication of hospitalization>
Clinical presentation of almost all the patients showed no indication for hospitalization. No cases required mechanical ventilation and no death was reported until 19th May.  The majority of the cases was discharged shortly after the admission, and placed to medical observation at home. Long term outcome is still unknown at this point, but clinical presentation is similar to seasonal influenza throughout the course of illness.  This suggests that most of the cases have no medical indication for hospitalization. Below is the case which seemed to have had indication for hospitalization.

Female, 20 y.o.
May 16th:  admission with fever above 38, headache (+), lower abdominal pain (++), arthralgia (+), diarrhea (+), general fatigue (+), cough (-), nasal discharge (-), sore throat (-), nausea (-).  Physical observation on admission was redness of the pharynx and tenderness at lower abdomen only.  Laboratory data was WBC 5100/mm3, Platelets 17.0 x 104/μl, CRP 9.2mg/dl with peripheral blood and rapid test with pharyngeal or nasal swab was A(-) B(-) and influenza A (H1N1) positive by RT-PCR.

Medication with oseltamivir and antispasmodic drug with fluid were given. She is still hospitalized today but clinical condition is gradually recovering. The cause of the abdominal pain is under investigation.

(2009/5/21 IDSC)

Copyright ©2004 Infectious Disease Surveillance Center All Rights Reserved.