Communicable Diseases PDF

States in the development of infectious diseases Infectious diseases represent the largest cause of childhood and adolescent deaths worldwide. In 2010, for example, they accounted for over 11 million deaths a year in low- and middle-income countries. In higher-income countries, although infectious...

States in the development of infectious diseases Infectious diseases represent the largest cause of childhood and adolescent deaths worldwide. In 2010, for example, they accounted for over 11 million deaths a year in low- and middle-income countries. In higher-income countries, although infectious diseases have a lower mortality than non-infectious dis- ease, they remain a topic of major public health importance for the following reasons: Globalisation (infectious diseases now spread rapidly around the globe) Re-emergence of old scourges (e.g. TB) Novel infections (e.g. severe acute respiratory syndrome (SARS), novel coronavirus) Evolution of existing pathogens leading to new risks (e.g. potential for zoonotic disease threats, pandemic influenzas) Resistance to therapeutic agents Hospital-acquired infections (e.g. methicillin-resistant Staphylococcus aureus (MRSA)) Burden of long-term conditions (e.g. HIV/AIDS) Viral cause of certain cancers (e.g. cervical cancer) Communicable Diseases Page 1 Communicable Diseases Page 2 Surveillance Surveillance is the ongoing systematic collection, collation, analysis, and interpretation of data and the dissemination of the information generated to facilitate disease prevention. In summary, surveillance provides information for action. Certain key infectious diseases are kept under constant surveillance in order to Detect trends Evaluate prevention and control measures Alert appropriate professionals and organisations to infectious disease threats Ireland In Ireland, the Health Protection Surveillance Centre (HPSC) is a unit within the Population Health Directorate of the Health Service Executive (HSE). The HPSC operates the Computerised Infectious Disease Reporting (CIDR) system to manage the surveillance and control of infectious diseases in Ireland and to monitor antimicrobial resistance. Health personnel return notification, outbreak, and enhanced surveillance forms electronically. The data are used to generate weekly infectious diseases and outbreak reports, which are published by the HPSC. International surveillance The value of global surveillance and of information sharing lies in Detecting the emergence of resistance in key pathogens Guiding infection control policies Engaging and prompting dialogue with policymakers Developing advocacy and educational programmes Stimulating research Global surveillance serves as an early warning system for epidemics and provides a rationale for coordinated public health intervention. When followed by swift public health intervention, the early detection of communicable diseases can reduce morbidity and mortality and mitigate the overall negative effects on international travel and trade. Global surveillance depends on strong national surveillance systems. For example, Public Health England houses the WHO reference laboratories for various infections (e.g. influenza; see Box 2G.1, TB, SARS), and it is the European Co-ordinating Centre for the Global Programme on Drug Resistant Tuberculosis. Examples of other international surveillance sys- tems include the following: European Centre of Disease Control (ECDC) infectious disease surveillance. European Antimicrobial Resistance Surveil- lance Network (EARSNet). Global Public Health Intelligence Network (GPHIN)-developed by Health Canada, this system trawls the Internet for communicable disease reports in various forums and news wires. Global Outbreak Alert and Response Network (GOARN)-a network of networks organised by the WHO-collects information from other sources, for example, GPHIN, WHO collabo- rating centres, and Pro-Med. Evaluating a surveillance system An evaluation of a surveillance system should consider The public health importance of the disease under surveillance The case definition (e.g. is it clear and consistent?) Details of the surveillance system (e.g. its objectives and components) Details of the analysis and reporting system Usefulness of surveillance (e.g. the actions that have been taken as a result of its findings) Conclusions and recommendations to improve the system Communicable Diseases Page 3 Communicable Diseases Page 4 Communicable Diseases Page 5 Communicable Diseases Page 6 Methods of control Communicable disease control aims to pre- vent the spread of infection in the population. In a healthcare setting, it is termed infection control and it aims to prevent cross-contamination, which may be: Between patients From healthcare workers to patients From patients to healthcare workers Prevention measures may be targeted at the case, the contacts, or at other potential sources of infection. Communicable Diseases Page 7 Design, evaluation, and management of immunisation programmes Development of a vaccination programme In developing a new vaccination programme, the following areas of work must be considered: Scientific evidence Programme strategy Administration Finance Vaccine purchase and distribution Communication Informatics In Ireland, the HSE National Immunisation Office website has up-to-date information for parents and professionals on the childhood immunisation schedule and on related topics, such as immunisation for travel (www.immunisation.ie/en). The Irish DH and the HSE take guidance from the Immunisation Advisory Committee of the Royal College of Physicians of Ireland, which in turn has representatives from DH, the HSE, the RCPI, the Northern Ireland DH and Social Services, and other relevant organisations. The commit- tee's guidance on immunisation is available on the HPSC website (www.ndsc.ie/hpsc). Vaccination strategies Immunisation schedules vary by country and vary according to local epidemiology, funding, a consideration of the risk, and ef ficacy of each vaccine for different age groups. An annual report published jointly by WHO and UNICEF lists the vaccination schedules of every country (WHO 2014). Communicable Diseases Page 8 In addition to national strategies, targeted vaccination strategies may be implemented in certain circumstances. Implementation of a vaccination policy In general, vaccine programmes are implemented at a local level using funds allocated by central government. Changes to the vaccination schedule After resources have been secured, vaccine manufacturers are invited to submit bids through a competitive procedure. Criteria for successful bidding are safety, efficacy, availability, price, and record of the company against previous con- tracts. Wherever possible, more than one supplier is chosen to minimise the likelihood of vaccine shortages. The communication of any changes to the vaccination policy in England is achieved through Letters from the chief medical officer, chief nursing officer, and chief pharmacist to all registered doctors, nurses, and pharmacists, respectively Website publicity Updates to the DH's 'Immunisation Against Infectious Disease' book (known as The Green Book') Outreach activities by a network of immunisation coordinators Public promotion and marketing A new promotion programme is then developed for the public, which may include leaflets; fact sheets; press, television, and radio advertisements; videos; and Internet materials such as 'question and answer formats, frequently asked questions (FAQS), and feedback facilities for questions. All new materials are pretested with the appropriate target audience, then amended accordingly, and their impact monitored. New data collection arrangements are set up in advance so that the vaccine coverage of a new initiative can be monitored. Evaluation activities may include: New disease surveillance arrangements to measure the impact of a new policy through laboratory-based data and/or disease notification data Seroepidemiological surveillance for gauging population impacts Market testing to evaluate the impact of any advertising that accompanied the introduction of new vaccines Adverse events are monitored by Expert groups that investigate any reported serious adverse events Records linkage (adverse clinical events recorded in hospital and/or primary care records are linked with immunisation data so that risks of adverse outcomes can be assessed) Local implementation activities may include A local implementation group, usually led by an immunisation coordinator, which may include a consultant in communicable disease control (CCDC) or consultant in health protection (CHP), a pharmacist, health visitor, community paediatrician, and a representative from primary care A local training programme for health professionals Communicable Diseases Page 9 Choices in developing an immunisation strategy Policymakers must consider many issues when developing immunisation policy. For example, oral polio vaccine (which is a live attenuated vaccine) leads to greater control of polio because it is more effective but can result in vaccine-related paralysis. Inactivated injected polio vaccine is safer and is therefore used by many countries in which polio has been eradicated (although there is the facility in an outbreak situation for reversion to the live vaccine). Immunisation strategy: Issues of policy makers Mass versus selective immunisation Live versus inactivated vaccine Age at vaccination Dose interval and the need for booster doses Outbreak response (including whether to create a vaccine stockpile) Surveillance Containment Investment in future research Outbreak response Vaccines are sometimes introduced in an attempt to control an epidemic. For example, in 2012, the DH in England decided that women should be offered pertussis vaccination after surveillance data showed a considerably higher incidence in both infants and the general population compared with the previous year. The pertussis was, there- fore, offered late in pregnancy to protect neonates both through transferred maternal antibodies and by limiting their potential exposure to infected individuals. Communicable Diseases Page 10 Outbreak investigations An outbreak may be defined as Two or more related cases of the same disease The occurrence of more cases of disease than expected in a given area, or among a specific group of people, over a particular period of time A single case of a disease of high public health importance, for example, anthrax, plague, SARS, diphtheria The objectives of controlling an outbreak are to Minimise the number of primary cases of illness through prompt recognition of the outbreak and through the identification and control of the source of the infection or contamination Minimise the number of secondary cases of infection by identifying cases and taking appropriate action to prevent any spread Prevent further episodes of illness by identify- ing continuing hazards and eliminating them or minimising the risk that they pose Introduce measures to prevent future outbreaks Outbreak control plans should include A description of the roles and responsibilities of each of the participating organisations and individuals Arrangements for informing and consulting the key personnel (e.g. directors of public health, the regional epidemiologist, relevant reference laboratories, senior managers from the health service and PHE, and the DH) Arrangements for liaison with local government, hospitals, and health authorities Facilities required to manage an incident (e.g. an incident room equipped with telephones, fax machines, and other efficient electronic communication systems - including arrangements for outside normal working hours) Outbreak control group An outbreak control group should generally be convened when an outbreak occurs and any of the following features apply: The disease poses an immediate health hazard to the local population There are a large number of cases Unexpected cases appear in several districts The disease is unusual and severe Investigation of an outbreak The management of an outbreak consists of five tasks that should be conducted concurrently - one of which is an epidemiological sequence that should be conducted serially. Communicable Diseases Page 11 Communicable Diseases Page 12 Emergency preparedness and response to natural and man- made disasters Natural and man-made disasters have the potential to cause widespread loss of life and long- lasting damage to health. Multi-agency response systems are required in order to plan and prepare for such disasters. Organisations that may be involved include Emergency services (police, fire, and ambulance) Health services Public health services Local government National government Meteorological organisations or other organisations with specialist knowledge e.g. Environmental Protection Agency International partners Natural disasters These include extreme weather events and other natural disasters such as temperature extremes, flooding, drought, storms, tsunamis, wildfires, earthquakes, volcanoes As well as their effects on physical and/or mental health, such events often interrupt utilities such as electricity and water and may hamper access to health services. Man-made disasters These include bombings, shootings, and the deliberate or accidental release of chemical, bio- logical, and radiological hazards. Actual and potential examples of such agents include Chemical: hydrogen cyanide, chlorine gas, nerve agents (such as sarin) Biological: anthrax, plague, smallpox Radioactive material The heightened threat of global terrorism requires thorough preparation to deal with deliberate releases of such substances. Preparation and response to disasters The acute response to any disaster should be coordinated by a multidisciplinary incident control team. The WHO's disaster management cycle may be used as a framework to help plan for and man- age such incidents. This cycle (which starts with prevention and ends with recovery) can be used alongside the risk management strategies. 1. Prevention Prevention entails taking steps to minimise the likelihood of an incident occurring; this may include the replacement of potentially hazardous substances, the installation of defences (e.g. flood barriers), legislation and regulation to minimise risks, and education and publicity to raise awareness. 2. Preparedness Preparedness involves gathering information on potential hazards, such as at-risk sites, developing an incident response plan, and training response teams including scenario exercises. 3. Detection and alert Communicable Diseases Page 13 3. Detection and alert This phase uses detection, surveillance, and alert channels to identify any incidents as early as possible. Examples of such systems include earthquake detection systems, health surveillance systems, and environ mental monitoring. 4. Response There are multiple potential interventions that may need to be implemented in response to a disaster, including the mobilisation of emergency services, terminating the release of any hazardous substance, and communication to the press and members of the public. 5. Recovery After the immediate effects of the disaster are over, further actions will be needed in order to return to normality and to learn from any mistakes. Actions may include providing support to victims, conducting risk assessments and health outcome assessments, and investigating of the cause of the incident. Communicable Diseases Page 14 Important infectious diseases The infectious diseases of public health importance may be grouped into the following categories (although many diseases will fall into two or more categories): Vaccine-preventable diseases Nosocomial infections Gastrointestinal infections Viral hepatitides Respiratory infections STIS Vector-borne diseases Other communicable diseases Vaccine-preventable diseases Communicable Diseases Page 15 Communicable Diseases Page 16 Communicable Diseases Page 17 Communicable Diseases Page 18 Nosocomial infections Communicable Diseases Page 19 Nosocomial infections Nosocomial (Healthcare-Acquired) Infections Healthcare-associated infections (HCAIs) are infections acquired as a result of health-care. Examples are MRSA, Clostridium difficile, glycopeptide-resistant enterococci (GRE), and Acinetobacter species. HCAI risk factors include Higher numbers of susceptible patients being treated (elderly patients or patients with severe or chronic diseases) Invasive procedures (e.g. indwelling lines, artificial ventilation) Immunosuppression (e.g. chemotherapy, post-transplant regimens) Increased patient movement between wards or between hospitals (often due to pressures on hospital beds) Wider use of antibiotics and the emergence of antibiotic-resistant microorganisms Higher rates of HCAIS are often found in specialist hospitals such as orthopaedic centres. However, with the move towards performing invasive procedures such as minor surgery in the community, primary care HCAIs may become more common. Measures to control of HCAIS include the following: Hand washing is generally the most important prevention activity. Universal precautions. Prudent antibiotic prescribing. Surveillance (e.g. the UK surveillance systems for MRSA, surgical site infection). Isolation and cohort nursing. Communicable Diseases Page 20 Gastrointestinal infections Four groups of people are identified as posing an increased risk of spreading gastrointestinal infection compared to the general population. Communicable Diseases Page 21 Communicable Diseases Page 22 Communicable Diseases Page 23 Viral hepatitides Communicable Diseases Page 24 Communicable Diseases Page 25 Interpretation of Hep C results Respiratory infections Communicable Diseases Page 26 Sexually transmitted infections The prevention of Sexually transmitted infections (STIs) involves Health and sex education Availability of low-cost condoms Early detection and prompt effective treatment Contact tracing and treating contacts Opportunistic or routine screening Surveillance Communicable Diseases Page 27 Communicable Diseases Page 28 Vector-borne diseases Other communicable diseases Communicable Diseases Page 29 New and emerging infections Emerging infectious diseases are commonly defined as those that have either newly appeared in a population or have existed but in either case are rapidly increasing in incidence or geographical range. The pattern of communicable disease occurrence is in constant flux. Current influences leading to emerging infections include Global travel Climate change Global trade and importation Urbanisation Population displacement Animal movements Changes in agriculture Emerging zoonoses Deforestation Bird migration Human conflict Antimicrobial resistance Genetic mutation/recombination Deliberate release Communicable Diseases Page 30  Deliberate release Current concerns Diseases attracting particular research attention and interest in health protection control policy include Smallpox Anthrax SARS Avian influenza and pandemic influenza West Nile virus Changes in vector distribution Pet travel scheme Leishmaniasis Hantavirus MRSA Vancomycin-resistant enterococci (VRE) Communicable Diseases Page 31 Organisation of infection control Organisation is required at several levels, including national and local government, and health services including hospitals and community services. National government are responsible for Infectious disease surveillance Providing specialist and reference microbiology and microbial epidemiology Coordinating investigation and cause of national and uncommon outbreaks Helping advise government on the risks posed by various infections Responding to international health alerts Local government A local authority's environmental health service has a duty to register, inspect, and investigate food premises. Environmental health officers have legal powers of enforcement and prosecution. Health services As part of their remit to promote health and prevent disease, health authorities/boards are responsible for the surveillance of disease and for identifying problems and establishing planning measures. Communicable Diseases Page 32 Microbiological techniques Basic understanding of the biological basis, strengths, microbiological techniques. There are two main methods of microbiological analysis - the traditional method involves growing a culture of the specimen in order to isolate and identify the microorganism (bacteria, fungi, viruses, and parasites). The alternative is a range of modern molecular methods that involve the identification of specific DNA or RNA (e.g. RNA transcriptase) within the specimen. TB, for example, once took 12 weeks to diagnose; now using molecular methods, it takes 24 hours. Main categories of methods used in microbiology laboratories Microscopy (including immunofluorescence) Culture Identification (e.g. typing of bacterial strain) Isolation of virus Drug sensitivity Serology (including immunoassay for antigen and antibody) Routine microbiological techniques Local hospital laboratories have tended to use traditional techniques. Reference microbiological techniques Molecular biological techniques form the basis of detecting and characterising an ever- increasing range of viruses, bacteria, fungi, and protozoa. Nucleic acid probes are commercially available for CMV, HPV, hepatitis B virus (HBV), hepatitis C virus (HCV), Chlamydia trachomatis, Neisseria gonorrhoeae, Streptococcus pyogenes, and mycobacteria, among others. Nucleic acid amplification systems are avail- able for the direct detection in clinical specimens of HCV, HIV, Mycobacterium tuberculosis (MTB), C. trachomatis, and N. gonorrhoeae. Immunoassays These are used in the detection of microbial anti- gens and offer the potential for rapid diagnosis. Examples include enzyme- linked immunoassays and direct immunofluorescence antibody assays. Communicable Diseases Page 33 Automated and semi- automated systems These fall into two main groups: Identification and susceptibility testing (some can provide results within a single working day) Blood culture systems (most true positive results are detected within 24-36 h). Some blood culture systems have been adapted for automated or semi-automated culture (e.g. for M. tuberculosis and other mycobacteria). These enable the identification and susceptibility results to be processed from large numbers of blood culture samples. Molecular methods undoubtedly have enormous potential in diagnosing infectious diseases. Communicable Diseases Page 34 International aspects of communicable disease control Globalisation has increased the risk of international spread of infectious diseases. Historically, the most important measures to stop the importation of infectious diseases were quarantine and trade embargoes. Increasingly, however, public health specialists are expected to balance the protection of public health with the avoidance of unnecessary disruption to trade and travel. Therefore, multilateral obligations and more nuanced port health measures are becoming increasingly important. International obligations International Health Regulations This is a multilateral initiative by countries to develop a global tool for the surveillance of cross-border transmission of diseases. Core obligations for WHO member states Countries are obliged to notify the WHO of public health emergencies of international concern, such as all cases of smallpox, SARS, wild-type polio, or a new subtype of human influenza. They must also Respond to requests for verification of information regarding urgent national risks Control urgent national public health risks that threaten to transmit disease to other member states Provide routine port inspection and control activities to prevent international disease transmission Apply the measures recommended by the WHO during public health emergencies Core obligations of the WHO In return, the WHO has a duty to respond to the needs of member states regarding the interpretation and implementation of its regulations. It must update these regulations (and their supporting guides) so that they remain scientifically valid. In addition, the WHO must publish recommendations for use by member states during public health emergencies of international concern. Port health In the United Kingdom, the regulations for ships, aircraft, and international trains give local authorities and port health authorities the power to appoint medical and non-medical port health officers who can prevent the entry of communicable diseases into the country. Circumstances requiring the intervention of port health staff include Outbreak of food- or water-borne disease on board a vessel Contamination of aircraft by faeces or vomitus Pests (rodents or insects) on board a vessel Passengers or crew who are suspected of being infected with viral haemorrhagic fever (VHF), yellow fever, plague, cholera, diphtheria, or TB The port medical inspector advises immigration officers on matters of health protection. Communicable Diseases Page 35