Medical Officer of Health


The Directors of Public Health and the Consultants in Public Health Medicine in each Department of Public Health 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 1953; Infectious 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. A summary of amendments to legislation can be found here.

Legislative functions of the Medical Officer of Health

The Medical Officer of Health 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.

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, clusters) and must comply with requests for information and directions as above. The Medical Officer of Health, in turn, must notify the Health Protection Surveillance Centre.

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 epidemiology in Ireland

The Medical Officer of Health 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 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 "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 - MOH Legislation and the GDPR


During the Covid-19 public health emergency of international concern, preventing every avoidable case of infection is the priority, and breaking every possible chain of transmission has been essential.  We have found some of the main infection risks for people is in congregate settings.  Protecting everybody in such settings sometimes requires sharing health information with the responsible person in those settings so that all necessary actions to prevent spread  of the infection are implemented quickly.  We only share the minimum information that is required.

As COVID-19 is a notifiable infectious disease, if you test positive for COVID-19, 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. 

For information about schools, see Covid-19 and Schools

For more information, see About Covid-19 Testing