Disease Early Warning System (DEWS) is a program by which health workers can detect signs of an epidemic at an early stage in order to prevent its occurrence. 

Goal & objective: The goal of DEWS is to minimize morbidity and mortality attributable to communicable diseases, and the objective is to detect an epidemic at its earliest possible stage.  

Epidemic: An epidemic is the occurrence of disease that is over and above its usual level in a population. Most of the epidemic-causing communicable diseases selected for DEWS in Pakistan have an average incubation period of one week. Thus, weekly assessment of disease incidence is crucial for the early detection of outbreaks and timely actions to be taken for initiating epidemic control measures.

  Figure I: Graph shows the beginning of an epidemic.

History: In 1996, World Health Organization (WHO) proposed the DEWS Action Plan for Pakistan. Training was provided to relevant officials and practitioners working in both public and private sectors in two pilot sites. The experiences from the pilot sites were instrumental in developing the linkage with the national Health Management Information System (HMIS) and revising the operational guidelines for expansion to other areas. To date, over 2000 health care professionals have been trained for DEWS in various districts.

In 1998, the Ministry of Health (MOH) established an Epidemic Investigation Cell (EIC) at National Institute of Health (NIH) with support of WHO. In 2003 the Global Infectious Disease Surveillance and Alert System (GIDSAS) of Johns Hopkins University also extended technical support to EIC. To date, the EIC has received nearly 200 reports of epidemics, investigating and responding to the majority of these with laboratory diagnosis and the provision of technical advice to district officials on how to control the epidemics.  

The type of epidemics dealt with are listed below:

   Figure II: Table of outbreaks investigated by EIC 

DEWS tools: DEWS utilizes three simple tools, a case definition and epidemic control handbook, a one page daily recording form and a weekly watch chart. The total cost of these tools is less than $2 per facility per year.

The diseases to be notified under the DEWS program have been selected on the basis of their public health importance and are divided into two groups:

Group A diseases: Reported immediately within 24 hours from detection. These diseases are: AFP/Polio, Hemorrhagic Fever, Cholera, Dengue, and Plague.

Group B diseases: Reported on weekly basis. These diseases are: Measles, Malaria, Diphtheria, Viral hepatitis, Pertussis, Typhoid, Influenza, Meningitis, HIV/AIDS, and Neonatal Tetanus.

The diseases included in DEWS are all, however, reported monthly through HMIS regardless of the level of their occurrence.

How can an epidemic be detected? Epidemics can be detected in three ways:

1.    If the weekly incidence of a disease doubles in comparison to the incidence in the previous 2 - 3 weeks.

2.    If there is geographical clustering of a disease in one area

3.    If the weekly number of cases of a diseases plotted on a graph crosses the Median Endemic Index line.

What are the criteria for epidemic threshold?

For endemic diseases like cholera, typhoid, viral hepatitis, meningitis, dengue, and malaria, the weekly number of cases for the current year (shown as bars in the graph below) are compared with the median figures (shown as area line behind bars in the graph below) of the same period in the previous 3 years.  An increase over the median figures, or Median Endemic Index (MEI), suggests an early warning of the occurrence of an outbreak. The graph below shows that the number of cases during the 8th week has clearly crossed the MEI and therefore must be investigated, as it could be the beginning of an epidemic.

    Figure III: Graph of Median Endemic Index

For diseases like Polio, Plague, and Dengue, the appearance of one single case should activate the DEWS to undertake immediate action.

Organizational Arrangements:

DEWS is a joint venture initiated by WHO and MOH, as represented by NIH and HMIS since 1997. At various levels DEWS activities are monitored as follows:

Federal Level: The DEWS field activities, data entry and analysis are implemented by the HMIS while the EIC of NIH is a partner. The EIC and WHO provide technical support and assistance in epidemic investigation, preparedness, and response.

Provincial Level: The Provincial HMIS Cell is a provincial focal office for implementation and prepares a provincial action plan.  It is also responsible for monitoring the activities.  The Directorate of Communicable Disease Control (CDC) at the Provincial Directorate of Health provides technical support to the Provincial HMIS Cell and helps in disease investigation of epidemics.

District Level: At district level the District HMIS Cell Officer acts as the focal person and initiates all necessary steps required for the implementation of the DEWS at district level. The officer will take prompt action when the weekly incidence of a particular disease has crossed the epidemic threshold level in any area. The action includes epidemic investigation and requesting NIH for laboratory support. 

Figure IV: Organization of DEWS at District Level

Health Facility Level. Basic Health Units, Rural Health Centers and Tehsil Headquarter Hospitals, Private Hospitals and NGOs are the sites where selected diseases will be monitored on weekly basis. In addition to public and private health facilities, private practitioners, traditional doctors (hakims) and  homeopathic  physicians participate in DEWS. These are provided with DEWS forms, which they fill and submit to the nearest public health facility every week on Monday. At the public health facility, data are recorded daily on the DEWS form and plotted every Tuesday on DEWS Weekly Watch Chart and inspected by a Medical Officer (MO).  

The DEWS Weekly Watch Chart posted on the MO’s office wall in each health facility serves as a visual aid for monitoring weekly cases of each epidemic causing disease. Utilizing the Endemic Index method, the MO plots cases of specific diseases on a weekly basis to see if any disease plot is crossing its median endemic index line.  

If the MO sees that any of the diseases has crossed the endemic line, then he/she immediately informs the Executive District Officer (EDO)-Health and investigates the problem.  If necessary, the EDO may directly inform the EIC at NIH Islamabad to assist in  investigating and identifying the epidemic-causing agent.  Besides informing NIH, the EDO is expected to undertake all immediate necessary measures for controlling the epidemic.