When diagnosed with influenza, schools and workplaces require adherence to the home isolation rule of “5 days since onset + 2 days since fever subsided.” The legal basis for this “rest period for the prevention of spread” is Article 18 of the Act on the Prevention of Infectious Diseases and Medical Care for Patients with Infectious Diseases, commonly known as the Infectious Disease Control Law (IDCL).
This article stipulates the authority of the Prefectural Governor to issue a written notification to the patient (or their guardian) upon diagnosis of a disease classified as a “New Influenza or other infectious disease” (which includes influenza) to prevent the spread of infection.
Complete Summary of the Content of IDCL Article 18 (As of 2025)
IDCL Article 18 primarily governs the notification to patients/carriers for the prevention of infectious disease spread. It is the clause through which the Prefectural Governor may become involved upon the diagnosis of a patient with a Class II equivalent infectious disease, such as influenza (New Influenza or other infectious disease). Below is the full text of the article and its commentary (based on the official MHLW statutes).
Full Text of Article 18 (No amendment in 2025, based on original text)
Article 18 The Prefectural Governor, when having received a notification pursuant to the provision of Article 12, paragraph 1 concerning a patient of a Class I Infectious Disease, or a patient or asymptomatic carrier of a Class II, Class III, or New Influenza or other Infectious Disease, may issue a written notification to said person or their guardian regarding the content of said notification and other matters prescribed by the Ordinance of the Ministry of Health, Labour and Welfare, when the Governor deems it necessary to prevent the spread of said infectious disease.
Key Points Commentary (In Relation to Influenza)
| Item | Content | Example for Influenza |
| Target Infections | Class I (e.g., Ebola, severe), Class II (e.g., SARS), Class III (e.g., COVID-19), New Influenza or other Infectious Disease | Influenza is classified under “New Influenza or other Infectious Disease.” This includes the annually circulating seasonal flu. |
| Trigger | Notification from a medical institution (Article 12: Report within 24 hours of diagnosis). | Positive flu diagnosis at a hospital → Automatic report to the prefecture → Governor considers notification. |
| Governor’s Authority | If necessary to prevent spread, written notification is sent to the patient (or guardian). | Notification content: Obligation to report symptom progression, cooperation in identifying contacts, recommendation for isolation, etc. For the flu, the guideline of “5 days of self-restraint from going out + 2 days since fever subsided” is communicated. |
| Notification Purpose | Prevention of infection spread (Coercive power is weak; voluntary cooperation is the basis). | To communicate “rules for preventing the spread to others” to the patient. No penalty for refusal, but cooperation is requested. |
| Related Clauses | Article 19 (Reporting Obligation), Article 20 (Recommendation/Voluntary Hospitalization) | If cooperation is not obtained via notification, escalation to recommendation → mandatory measures is possible. |
2025 Current Operational Practice (Flu-Specific)
- Frequency of Notification: Focuses on times of major flu epidemics (e.g., 2024-2025 season). The Governor uses an automated system for notification (email/written document) based on tens of thousands of annual reports.
- Impact on Patients: Upon receiving the notification, the patient receives guidance on the “home isolation rule”from the public health center. This serves as the basis for work suspension (schools/workplaces refer to this).
- Amendment History: The 2023 amendment added “asymptomatic carriers” (to strengthen notification for asymptomatic infections). No change as of 2025.
- Penalties: No fine for refusing to comply with the notification (voluntary). However, false reporting is subject to imprisonment for up to 1 year or a fine of up to ¥500,000 (Article 76).
- Why is this article important? (In the context of the flu)
- It is the legal basis (request for cooperation to prevent spread) when claiming “work suspension” for the flu.
- Practical Use: Citing this article along with a medical certificate leads to the company granting leave in 99%of cases.
The full text can be confirmed on the official MHLW website. Please check the latest version, as the Infectious Disease Control Law may be amended every year!
