Medical Officer of Health: Role and Legal Basis

Area Directors of Public Health, Consultants and Specialists in Public Health Medicine (CPHMs/SPHMs) in each Department of Public Health, and the Director of National Health Protection and SPHMs/CPHMs in the National Health Protection Service of Ireland, implement the Medical Officer of Health (MOH) legislation.

The Medical Officer of Health (MOH) has the responsibility and authority to investigate and control notifiable infectious diseases and outbreaks, under the Health Acts 1947 and 1953Infectious Disease Regulations 1981 and subsequent amendments to these regulations. Also, the Health (Duties of Officers) Order, 1949 describes the additional responsibilities of the Medical Officer of Health (MOH). A summary of amendments to legislation can be found on the HSE website.

Legislative functions of the Medical Officer of Health
The Medical Officer of Health (MOH) function is necessary for health protection, including the health security of the state. The state has identified the following medical functions as being so important that they are mandatory and they can be summarised as the investigation, prevention and control of notifiable infections and outbreaks:

"On becoming aware, whether from a notification or intimation under these Regulations or otherwise, of a case or a suspected case of an infectious disease or of a probable source of infection with such disease, a medical officer of health, or a health officer on the advice of a medical officer of health, shall make such enquiries and take such steps as are necessary or desirable

  • for investigating the nature and source of such infection,
  • for preventing the spread of such infection
  • and for removing conditions favourable to such infection"

(Infectious Diseases Regulations, 1981- Regulation 11)

SI No. 707 of 2003 - Infectious Diseases (Amendment) (No. 3) Regulations 2003 added disease clusters and changing patterns of illness that may be of public health concern to the conditions that must be notified to the Medical Officer of Health (MOH).

Authority for this function
"A person who refuses to comply with a requirement or direction given or a request for information made in pursuance of any of the provisions of these Regulations shall be guilty of a contravention of these Regulations”.

Infectious Diseases Regulations, 1981- Regulation 19

Notification and Surveillance
Under the Infectious Diseases Legislation, medical practitioners must notify the Medical Officer of Health of notifiable events (cases of notifiable infections, outbreaks and clusters) and must comply with requests for information and directions as above. The Medical Officer of Health (MOH), in turn, must notify the Health Protection Surveillance Centre of such events. Further details on the notification process are available on the HPSC website.

Detention and isolation of a person who is a probable source of infection
Under Section 38 of the Health Act 1947 and Section 35 of the Health Act 1953 the responsibilities are described.

The mandate for human epidemiological investigation in Ireland
Epidemiological investigations are often required and undertaken by the Medical Officer of Health (MOH) as part of investigation of cases and outbreaks under the Infectious Diseases Regulations 1981. The epidemiological investigations can be:

a. descriptive where demographic, risk factors, clinical details and other characteristics of cases are gathered,
b. analytical where characteristics of cases are compared with others who do not have infection, which can identify risk factors (e.g. food consumed, risk behaviours) associated with infection.

Through these investigations, risks associated with infection can be identified, and targeted public health interventions can be designed and implemented in order to prevent transmission, control spread of infection and control an outbreak.

These investigations are core public health response functions of the Medical Officer of Health (MOH) and are not research. When responding to outbreaks and undertaking investigations with direct public health implications, ethical approval is not required.

Most outbreak investigations are undertaken by a Medical Officer of Health (MOH) in the geographic area where the cases or outbreak is occurring. If an outbreak is national or international, the epidemiological investigation is undertaken by the Director of National Health Protection/National MOH.

For epidemiological investigations of non-infectious hazards, the Medical Officer of Health (MOH) shall inform themselves “ respects the causes, origin and distribution of diseases in the county”. (Health (Duties of Officers) Order, 1949 Schedule)

Public health risk assessment (PHRA)
The Medical Officer of Health (MOH) shall inform themselves “as respects all influences affecting or threatening to affect injuriously the public health in the county". (Health (Duties of Officers) Order, 1949, Schedule)

Advisory role to other authorities
The Medical Officer of Health (MOH) "shall advise the county council generally in relation to the health of the people and the provision of health services, sanitary services and housing accommodation(Health (Duties of Officers) Order, 1949 Section 1).

As some of the functions of county councils have been transferred to other authorities, for example HSE for health services and Irish Water for sanitary services, advice is given to the appropriate authorities.

These functions combine to provide a mandate for health intelligence, commonly defined as the capturing and utilisation of knowledge to support decision-making to improve the health of the population.

Confidentiality and Data Protection
"Data protection law does not stand in the way of the provision of healthcare and the management of public health issues; nevertheless there are important considerations which should be taken into account when handling personal data in these contexts, particularly health and other sensitive data" (Data Protection Commission).

During an infectious disease investigation, the Medical Officer of Health (MOH) and/or their team will sometimes need urgent access to information, or to share it with the responsible person in a setting in order to protect individuals and the public. While processing of such personal health information is allowed on public health grounds, all information provided to the MOH is treated with utmost sensitivity and confidentiality possible and in line with the requirements of the General Data Protection Regulation (GDPR). See more information on MOH Legislation and the GDPR.

For notifiable infectious diseases, if you test positive, it is required and permitted under law (Infectious Diseases Regulations 1981 as amended and GDPR) for you to share details of your contacts with Public Health (Departments of Public Health and Contact Tracing). All information is treated with the strictest confidence and protected by data protection legislation. To protect your confidentiality, your name will not be disclosed to your close contacts.

Data governance
The processing of personal data and collection of information as part of analytical epidemiological investigations is provided for under Article 9, 2(i) of the General Data Protection Regulation, which permits the processing of personal data if:

“processing is necessary for reasons of public interest in the area of public health, such as protecting against serious cross-border threats to health or ensuring high standards of quality and safety of health care and of medicinal products or medical devices, on the basis of Union or Member State law which provides for suitable and specific measures to safeguard the rights and freedoms of the data subject, in particular professional secrecy;”

The Infectious Diseases Regulations 1981 fulfil the member state law requirement. Under these regulations, there is an exemption for analytical investigation as a public health function to prevent and halt transmission of notifiable diseases.

Created: July 2023