Prevent the Infected from Mosquito Bites to Achieve a Rapid Dengue Control with an Active Community Surveillance Network A new approach to be combined with current eradication programmes

ඩෙංගු මර්දනය සඳහා ආසාදිතයින් මදුරුවන්ගෙන් ප්‍රවේසම් කිරීම අරමුණු කරගනිමින් ඉදිරිපත් කෙරුණු යෝජනා වලිය. මෙය විවිධ පාර්ශව වෙත යොමු කෙරුණද සතුටුදායක ප්‍රතිපල නොලැබුන නිසා කාට හෝ ප්‍රයෝජනයක් ගත හැකි පරිදි මෙසේ ව්වෘත අවකාශයේ සටහන් කරමි. 

Prevent the Infected from Mosquito Bites to Achieve a Rapid Dengue Control with an Active Community Surveillance Network

A new approach to be combined with current eradication programmes

Background

It’s a fact that Dengue is a mosquito-borne Viral infection caused by closely related but distinct 4 types of virus that causes dengue. These serotypes are named as DEN1, DEN2, DEN3, and DEN4. If a person gets infected by one serotype and then after some time, gets infected with a different serotype he has high chance of going into a severe form of dengue illness. (1)

Dengue virus is transmitted by the 2 mosquito species named aedes aegypti and aedes albopictus.  They mostly live in habitats around urban areas, where man made water containers are available for hatching. The albopictus mosquito has the ability to adopt to new condtions and shelter in very small habitats. They mainly feed during the day time specially during early morning and evening. (2)

Problem

This epidemic of Dengue Virus is devastating the day to day life of the citizens of Sri Lanka. Now it is no longer a disease of the city, it has stretched its limits to every directions inside the country. Despite all strenuous measures taken for the elimination of breeding sites aiming to reduce the mosquitos, dengue cases are rising day after day. We need to review our strategies and basics of epidemiology to address the pitfalls of current programme , thereby take measures to amend or enhance as needed.

Even though dengue is a vector-borne infection biologically, current trends of the epidemic gives a pattern of an infectious disease like influenza or ebola. It is because the proportion of infected individuals are high, it is so easy for the mosquito to fine an infected person and transmit his virus to the other. So if we need to tackle this epidemic we need to consider the strategies taken to control such infectious disease as well.

In an infectious disease the key factors responsible for the control are

·       Number of susceptible people

·       Duration of infectiousness and

·       Degree of mixing of infected and healthy individuals.

When the susceptible number of individuals increases, the number of expected patients are increased. When duration of infectiousness is long, more susceptible for another healthy person to catch the disease. Finally if the mixing between infected and healthy individuals happens at a higher degree the transmission is more too. (3)

Therefore if we take dengue as an infectious disease even for a small duration, we need to control whatever possible from these three. We cannot reduce the susceptible number because in dengue total population is affected and it is almost a constant. And also we can’t reduce the duration of infectiousness because there’s no antiviral or such drug to kill the virus. So we are only left with the option of limiting the mixing. This is achievable by introducing a modified isolation method, which is similar to the quarantine of infected people in an infectious disease.

Therefore the next question is “how to isolate the ‘infectious’ individuals”. For this we need to understand the natural course of the dengue infection. The disease is transmitted through a female mosquito. This mosquito acquires the virus from an infected individual when it feeds on his blood. Inside the mosquito it takes 8-10 days for dengue virus to incubate. Then it transmits the virus to a healthy person while it feeds on his blood. After getting infected, the virus multiplies inside human, and makes him the main carrier of the virus. It serves as the source of virus for the uninfected mosquitos. Then it incubates inside human body for a time period of 4-7 days. Sometimes his time period can be longer than this. Then the virus rises to a level at which the individual starts showing symptoms, mainly the ‘fever’. This individual can pass the virus to another mosquito after showing these symptoms. In other words, majority of the transmission occurs from a patient who has viremia, and during this viremia period many patients show symptoms, at least a fever. Experimental studies have shown that the individual can be infectious from only 24 hrs before the onset of the disease. And this period is not confirmed with statistical models. However this viremia or the infectious period usually last for 5 days. Then majority of the patients are free of transmittable virus in their blood.  (4), (5)

So it is apparent that we have an opportunity to identify the infectious individuals with the onset of fever and other symptoms. If we can isolate these fever patients who are suspicious to be having dengue infection during those 5 days, we will be able to limit the transmission.

Objectives

1.       To improve the current dengue eradication programme by isolating the infectious individuals using mosquito nets.

2.       To establish a good surveillance network at both hospital level and community level.

3.       To actively participate the community for the surveillance network.

4.       To initiate health promotion of the community with the help of surveillance network

5.       To enhance the current breeding site elimination program using this community surveillance network.

Methodology

This programme is expected to be carried out at both hospital and community. There should be centralized bodies to coordinate with each other and with other relevant authorities. Activities at the hospital should be monitored by “Hospital Dengue Surveillance Centre (HDSC)” and Activites at the community should be monitored by “Community Dengue Surveillance centre (CDSC)”. The current OPD triage system can be used as HDSC and the preferably MOH office should act as the CDSC.

Activities of the HDSC can be summarized as follows.

• 1.       Run a fever section at the OPD
• 2.       Select the suspicious individuals who come to the OPD and get their details. Subscribe the to the surveillance data base. ( dengue Sentinel System data base can be used for this purpose )
• 3.       Ensure the surveillance of all dengue patients at the wards.
• 4.       Coordinate with the CDSC and other health programmes to ensure integrity of surveillance island wide.
• 5.       Guide and monitor the vector control at the hospital premises.
• 6.       Ensure the safety of healthcare workers from getting dengue virus.

Activities of CDSC can be summarized as follows

• 1.       Establish a good community based surveillance system with participants from the health sector and community. Give the community representatives sufficient health education and training. Regularly supervise their activities.
• 2.       Establish a good coordination with HDSC and other relevant authorities to ensure the integrity of surveillance System Island wide.
• 3.       Supervise the breeding sites elimination in the area.

Role of community representatives

• 1.       Trace the suspicious patients who were sent for ambulatory care at home and ensure that they are kept inside a mosquito nets 24 hrs, getting the medical care advised, regular blood tests and clinical assessment is done, family members are using repellents, elimination of breeding sites and arrange fogging.
• 2.       Send the feedback upstream
• 3.       Actively monitor emerging fever patients from surrounding areas and direct them to health care followed by advices as above.

Expected outcomes.

• 1.       To block the transmission from the patients who are coming from outside the area and thereby reduce the dengue incidence of the area in-situ.
• 2.       To reduce the incidence of dengue fever in areas where dengue density is high.
• 3.       Bring the cases level to the baseline level rapidly.
• 4.       Improve the fundamental knowledge about dengue among the public.

Expected drawbacks

• 1.       Asymptomatic infections though a small percentage of them are capable of transmitting the virus, can be missed.
• 2.       The current focus of community about the importance of eliminating the breeding sites can be shaken.
• 3.       Practically we will face difficulties implementing the surveillance centers in the aspects of finding infra-structure, staff, funds, etc.

References

1.       World Health Organization. 2017. Dengue Control. [ONLINE] Available at: http://www.who.int/denguecontrol/disease/en/. [Accessed 19 July 2017].

2.       Scitable. 2017. Dengue Transmission. [ONLINE] Available at: https://www.nature.com/scitable/topicpage/dengue-viruses-22400925. [Accessed 19 July 2017].

3.       Centre for Disease Control and Prevention. 1995. Emerging Infectious Disease. [ONLINE] Available at: https://wwwnc.cdc.gov/eid/article/1/1/95-0102_article. [Accessed 19 July 2017]

4.       CAB Directt. Dengue: Its History, Epidemiology, Mechanism of Transmission, Etiology, Clinical Manifestations, Immunity, and Prevention.. [ONLINE] Available at: https://www.cabdirect.org/cabdirect/abstract/19261000360. [Accessed 19 July 2017].

5.       Pubmed. 2012. The Incubation Periods of Dengue Viruses. [ONLINE] Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3511440/. [Accessed 19 July 2017].