BIO4503 APPLIED EPIDEMIOLOGY MONITORING AND SURVEILLANCE IN EPIDEMIOLOGY 1 Dr. Carmen Aceijas, PhD

Lecture description PUBLIC HEALTH SURVEILLANCE. DEFINITION AND MAIN FEATURES CASE DEFINITION FOR SURVEILLANCE SYSTEMS TYPES OF PH SURVEILLANCE USE OF SURVEILLANCE SYSTEMS DATA FOR SURVEILLANCE SYSTEMS DEMOGRAPHIC DATA MORTALITY DATA MORBIDITY DATA

PUBLIC HEALTH SURVEILLANCE PH Surveillance: “Systematic, continuous monitoring of the incidence and transmission of a disease” WHO Public health surveillance site: Most countries have systems in place to monitor certain diseases [e.g.: meningitis, anthrax and TB]. They operate through mandatory reporting of cases [NOTIFIABLE DISEASES]. –Mandatory for all health providers involved in the detection of cases –Reporting of cases [number] –Reporting of risk factors also included [e.g.: smoking, alcohol consumption] 3

PUBLIC HEALTH SURVEILLANCE. CASE DEFINITION FOR SURVEILLANCE SYSTEMS Surveillance systems to be efficient require strict criteria and standard methods. Criteria for case definition: –1. clinical findings –2. laboratory results [to confirm/reject clinical diagnosis] –3. epidemiological data describing time, place and type of individuals affected 4

PUBLIC HEALTH SURVEILLANCE. TYPES OF PH SURVEILLANCE PASSIVE - Reporting of cases in automatic and routine ACTIVE -Rarely carried out routinely -Uses periodic visits to institutions [e.g.: hospitals] to collect required data. -Used to monitor the spread of a new disease or outbreak -Costly and labour intensive Limitations of any surveillance system: sensitivity is not 100%. Therefore, estimates are conservative. 5

WHAT DOES PUBLIC HEALTH SURVEILLANCE ALLOWS US TO MEASURE? BASELINE -Routine monitoring allows the determination of what is “normal” in a given population regarding the spread [incidence rates] of a given disease. -Affected by changes in case definition and/or data collection methods TIME TRENDS -Focus on variations in disease incidence. -Useful to: -Identify outbreaks -Measure variations in the disease incidence over time [time trends] -Assess impact of PH interventions [e.g.: effect of vaccination policies] 6

WHAT DOES PUBLIC HEALTH SURVEILLANCE ALLOWS US TO MEASURE? (II) TIME TRENDS [cont] Reliability of measurements affected by: - Awareness of a condition leads to increase of reporting - In post-outbreak times, health professionals will tend to detect more cases [case-ascertain bias]. PATTERNS OF DISEASE E.g.: Seasonal variations observed in cardiac mortality winter: higher mortality winter + older age: higher mortality Specific disease patterns must be incorporated in the baseline calculations. 7

DATA FOR SURVEILLANCE SYSTEMS Demographic data Mortality data –Completeness of mortality statistics –Health indices derived from mortality data and other uses Morbidity data –Communicable diseases – health centres and hospital data – other sources of morbidity data

Demographic data Demographic data is routinely collected at country level in the census [UK is every 10 years] Type of indicators included: sex, age, geographical distribution, ethnicity, religion, level of education and so on Annual statistical projections are also carried out [in UK by the Office for National Statistics [ONS]] ONS also implements the continuous multipurpose survey “General Household Survey” [GHS] which collects information on a rather wide range of demographic aspects of our society [e.g.: employment, education, sports and leisure engagement]

Demographic data [cont.] Demographic data is essential to understand the real impact of diseases and the resources available to tackle them. –E.g.: The impact of 1,000 cases of newly diagnosed TB is very different in a 1,000,000 population compared to 10,000,000 population. Why? –E.g.: 1,000 new cases of TB represent a very different challenge in a well established health service compared to a newly established system. Why? –E.g.: 1,000 new cases of TB in a high GDP population is very different than in a low GDP population. Why?

Where to find population data Go to: In pairs, chose a country and decide what demographic indicators of those available you would like to use for a “newly established surveillance system” in that country for a health disease of your choice ½ max hour exercise

Mortality data [I] Data on mortality is collected at country level via death certification. Data on mortality is used for health analysis as it is a good proxi indicator of the health of a population and the main diseases affecting it. In UK, NOS is the body who provides with the guidelines to medical doctors to fill in the “medical certificate of cause of death”. There are three main types of certificates: stillbirth, neonatal and others. 12

Mortality data [II] Routine mortality statistics require that for each death a single cause of death is identified. WHO’s guidance on it is: –The disease or injury that initiated the train of events leading to death. –The accident or violence that produced the fatal injury/ies However, other significant [to the death] health issues will be recorded as well. The International classification of disease [ICD] is used to assign a single code to each possible cause of death. ICD is a standard diagnostic tool for epidemiology, health management and clinical purposes. The ICD 10 [current version] can be accessed at: WHO collates country data to produce the analysis of deaths by sex, age group and cause of death.

Completeness and accuracy of mortality statistics Completeness refers to the proportion of all deaths that are registered. Developed countries register all deaths but this not the case for many developing countries. Additionally, accuracy can be compromised by things such errors in the clinical diagnosis, errors in filling in the certificate or errors in ICD code assignment. Factors affecting poor reporting: –Infrastructure [e.g.: fewer medical doctors and hospitals in rural areas] – Religious and cultural beliefs [e.g.: some countries refuse to acknowledge they have HIV/AIDS within their borders] – country specifics: some countries include deaths of nationals abroad as their own statistics. –A way to ascertain problems in completeness of reporting: to divide annual deaths reported by total deaths estimated for the whole population

Mortality data and health indices Mortality data is also calculated to calculate a number of health indicators. E.g.: neonatal and infant mortality is used as an index of general health and the provision of care for a large population. Other routinely collected indicators fed by mortality information are maternal health and standardized mortality ratios.

MORBIDITY DATA We need to know the burden of disease [both from communicable and NCD] to plan services and to provide the basic information for epidemiological and clinical research [to formulate research questions on the possible determinants of diseases].

MORBIDITY DATA. COMMUNICABLE DISEASES [I] Data on communicable diseases are collected and reported by public health agencies. In UK the list of notifiable diseases [n=30] is published by PHE. It can be accessed at: tionsAZ/NotificationsOfInfectiousDiseases/ListOfNotifi ableDiseases/ tionsAZ/NotificationsOfInfectiousDiseases/ListOfNotifi ableDiseases/ Doctors are required by law to notify both suspected and confirmed cases of notifiable diseases.

MORBIDITY DATA. COMMUNICABLE DISEASES [II] WHO plays a key role in monitoring outbreaks of communicable diseases. The international agreement for the monitoring of communicable diseases was achieved in 1951 under the name of “International Sanitary Health Regulations” and was further updated in 1969 under the name of “International Health Regulations” They were originally aimed at controlling six diseases: cholera, plague, yellow fever, smallpox, relapsing fever and typhus. Different factors might affect the completeness and accuracy of records of communicable diseases. Most of them are the same issues affecting mortality reports too. An specific factor for incompleteness of infectious diseases: they person affected needs to go/taken to a health facility

MORBIDITY DATA. NCDs Probably the best established reporting system outside communicable diseases are the cancer registers. Cancer registers allow the monitoring of trends of incidence, prevalence and survival rates of all cancers and also collect information on exposures that serves the basis for epidemiological research The UK National Cancer Intelligence Network [NCIN] part of PHE receives regional data and produces secondary analysis and research. Other NCDs with good established registers are diabetes and heart diseases among others. Surveillance systems for chronic diseases are also used to organise recall of patients for check ups and medication review.

MORBIDITY DATA.CONGENITAL DISEASES. Following the tragedy of thalodomine [prescribed to pregnant women in the 60s to prevent morning sickness] and found to cause limb malformations it was clear the need to monitor congenital diseases. The thalodomine tragedy triggered the creation in UK of the National Congenital Anomaly System [NCAS] in

Health centres and hospital data Information collected by health centres and hospitals is very wide in type and serves different purposes. Generic data collected in health centres and hospitals… Patient’s contacts, Hospital stay [length] Interventions implemented [e.g.: surgical interventions] Patients outcome Patients perceptions And so on…

Health centres and hospital data [II] Sources of incompleteness and lack of accuracy in data expected from health providers: -Human error -Private sector and especially “complementary” medicine centres not always obliged to report -No everybody access health care when is needed [e.g.: gender bias] -Access to health care depends on “severity”

RECOMMENDED READING WHO and CDC [2010] “Integrated disease surveillance and response in the African region” Bray F et al (2014) Planning and Developing Population- Based Cancer Registration in Low- and Middle-Income Settings. WHO/IARC. WHO Immunization surveillance, assessment and monitoring. TO LEARN MORE… nce_publication/en/index.html nce_publication/en/index.html Data, statistics and graphics: