4.2 Epidemiological surveillance


Once an outbreak has been confirmed, epidemiological surveillance must be stepped up. The goals of the surveillance system are:
– to identify new epidemic foci early;
– to monitor the evolution of the outbreak;
– to arrange for appropriate patient care;
– to evaluate response activities.

4.2.1 Case registration

The registers (Appendix 5) are the foundation of all data collection. The decision is whether to set up special registers for measles cases or to use the existing registers. Whichever approach is chosen, registers must be available in every facility, and must remain there.

The following information should be collected for each measles case: admission date, name, address, sex, age, diagnosis, treatment, treatment outcome, and immunisation status.

4.2.2 Description of the epidemiological surveillance system

Data

Basic information
At the end of every epidemiological week, all health care facilities send their weekly measles data up to the next higher level. In order not to weigh down surveillance, only the basic information (number of new cases and deaths) are transmitted on a weekly basis.

Supplementary information
Immunisation status of cases, and age group: these data must be entered at health centres and hospitals, but are not routinely transmitted to the next level. They will be used only if more detailed analysis is needed.

Zero reporting
If there were no cases seen over the course of the week, that information should be transmitted. This is known as "zero reporting". Failing to report is equivalent to missing data, and does not mean there were no cases.

Data transmission

Use the fastest means of communication available to transmit data (telephone, SMS, MMS,email, radio, etc.).

Every week, the person in charge transmits the number of cases and deaths, either by the standard, pre-established forms or by telephone. If transmitting the data verbally, one paper copy of the report is routinely sent to the next higher level and the other is kept in thefacility.

Every visit to a health care facility in an affected region (supervision of treatment activities, supply or vaccination) is an opportunity to collect, verify and transmit data.

Data compilation

Data are usually compiled and analysed at the district level (incidence rate, attack rate and case fatality rate) and then transmitted to the regional level. After compilation and analysis at the regional level, the data are transmitted to the national level.

At each level, the person responsible for surveillance checks the data for completeness and promptness in transmitting them. He enters them, verifies that they tally with the transmitted forms, and links them to the laboratory data, if applicable.

Data analysis

The analysis (Time - Place - Person) is done at every level, every week, as soon as the epidemic season begins. This is a crucial step for identifying and management outbreaks.

Displaying the data in the form of tables, graphs (Appendix 6) and maps facilitates the analysis. While the software tool makes it easier to organise the data, it is not absolutely necessary at all levels. At the clinic level, for example, a simple graph posted on the wall and updated each week will show any uptick in the number of cases and allow case fatality rate monitoring.

Laboratory surveillance

After the first few samples (confirmation and genotyping), it is not necessary to monitor continually throughout the outbreak. For laboratory surveillance, consult the country’s national recommendations.