Dengue Fever is a rapidly emerging vector born viral disease associated with significant public health impact. It is responsible for about 50 –200 million cases, 20,000 deaths annually. It had sporadic distribution in the 19th century and nine countries around the world reported Dengue fever epidemic in the year 1970. Since then the global epidemiology of Dengue fever changed rapidly and currently it is endemic in 110 countries with 2.5 billion populations at risk in the tropical and subtropical regions. Dengue fever is one of an International Public Health Emergency Concern (PHEC) as recommended by World Health Organization and it is now one of WHO reportable diseases (1).
In Africa, Dengue fever reported in at least 22 countries but is likely to be present in all of them with 20% of the population at risk (2).
In Ethiopia Dengue fever has become a new emerging public health problem. The first outbreak of Dengue fever appeared in Dire Dewa city administration, 2013, where 9441 cases were recorded. The second Dengue fever outbreak occurred in Adaar woreda, Afar Region where 708 cases reported 2014. The third outbreak was occurred in Godey town, Somali Region where 125 and 3 deaths were reported in 2014.
Infection with Dengue viruses present with severe headache, fever, muscle and joint pain, characteristic skin rash and in a small proportion of cases the disease develops into the life-threatening dengue hemorrhagic fever, resulting in bleeding, low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome. There is no specific treatment for dengue/ severe dengue, but early detection and access to proper medical care lowers fatality rates below 1%. Dengue prevention and control solely depends on effective vector control measures (3).
Dengue fever transmitted by a day biting mosquito AidesHYPERLINK “http://en.wikipedia.org/wiki/Aedes_aegypti" HYPERLINK “http://en.wikipedia.org/wiki/Aedes_aegypti"aegypti which bite particularly during in the early morning and in the evening, but they are able to bite at any time and thus spread infection at any time of day all during the year. There are four distinct serotypes of Dengue virus (DEN–1, DEN–2, DEN–3, and DEN–4) and infection with one type usually gives lifelong immunity to that type, but only short-term immunity to the others. Humans are the primary host of the virus, but it also circulates in nonhuman primates.
Subsequent infection with a different type increases the risk of severe complications (4).
In clean and unfavorable environment for Aides mosquito to reproduce, the infection of Dengue fever is rare. As there is no commercially available vaccine, prevention is sought by reducing the habitat and the number of mosquitoes and limiting exposure to bites. Several factors have combined effect to produce favorable epidemiological conditions for Dengue fever in developing countries such as rapid population growth, rural-urban migration, inadequate basic urban infrastructure, unreliable water supply leading householders to store water in containers close to homes and increase in volume of solid waste, such as discarded plastic containers and other abandoned items which provide larval habitats in urban areas. Increased air travel and breakdown of vector control measures have also contributed greatly to the global burden of Dengue fever and Dengue Hemorrhagic Fever (DHF) (2).
In Godey town acute febrile illness cases become increased started from May 27, 2015 and serum sample from one suspected Dengue fever cases become positive. A team from EPHI, WHO and Somali regional health bureau deployed to Godey town to investigate the outbreak.
We investigated to identify risk factors of Dengue fever outbreak in order emphasize and commence both short-term long-term control and preventive measures.
Literature Review
An estimated 50 million Dengue infections occur annually and approximately 2.5 billion people live in Dengue endemic countries both tropical and subtropical areas. Although Dengue fever exists in the WHO African Region, surveillance data are poor. Outbreak reports exist, although they are not complete, and there is evidence that Dengue outbreaks are increasing in size and frequency. It has mostly been documented in Africa from published reports of sero-surveys or from diagnosis in travelers returning from Africa, and Dengue fever cases from countries in Sub-Saharan Africa. For eastern Africa, the available evidence so far indicates that DEN–1, –2 and –3 appear to be common causes of acute fever. Examples of this are outbreaks in the Comoros in various years (1948, 1984 and 1993, DEN–1 and –2) and Mozambique (1984—1985, DEN–3) (5).
A cases control study to assess risk factors associated with an outbreak of Dengue fever in Brazil in 2001 showed the topographic location of the house was an important risk factor: Other risk factors associated with Dengue fever were plants with temporary water pools on the property, a gutter to collect rainwater, water storage in the house, uncovered water storage container, absence of waste collection and empty glass or plastic containers suitable as putative breeding sites for Aides aegypti (5)
According to study conducted on factors associated with spread of Dengue fever in urban. Lahore, Punjab, Pakistan, 2013, the presence of indoor stagnant water, presence of indoor larvae and non-use of repellents were found to be independent determinants of Dengue fever infection.On this study more men than women and younger rather than older people were affected which is consistent with other findings and may be because these groups are more likely to be Outdoors and, therefore, be exposed to mosquitoes (6).
The other study onrisk factors associated with an outbreak of Dengue fever/Dengue hemorrhagic fever in Hanoi, Vietnam 2014, indicated that living in rented housing, living near uncovered sewers, and living in a house discharging sewage directly into ponds were all significantly associated with DF/DHF (7).
A survey conducted in India showed Dengue cases were more during September to November only, which is similar to most of the previous outbreaks in India. It may be because this season is very favorable for high breeding of the vector, i.e., Aides aegypti. This seasonal outbreak of disease transmission is very important at local level for effective control measures. The study draws attention toward the male, young adult age group (8).
Also a study done in Zambia reveled that Aides aegypti commonly bites during the day and therefore the use of Long Lasting Insecticidal Nets (LLINs) would not be expected to provide a barrier between the humans and this Dengue fever transmitting vector. Considering the outdoor activities participated in during the day including farming, fishing, and socializing, the population may be at risk of being bitten by the vector (4).
Vector control is known to be a good method for prevention of vector borne diseases. There are several reports from India which have demonstrated resistance of mosquito vector with anti larval substances like DDT and dihedron but susceptibility to malathione is reported. Temephos is relatively more effective in controlling Aides aegypti, followed by function, Malathion and DDT. Per domestic thermal fogging reduced the resting and biting for the 3 days after treatment, whereas indoor fogging suppressed adult populations for 5 days (8).
Ethiopia reported Dengue Fever outbreak for the first time in 2013. During an international consultative workshop in 2014 key recommendations were forwarded for strengthening dengue prevention and control in Ethiopia: expand the scope of the existing Malaria Control Program to include Dengue Fever and other Vector-Borne Diseases; initiate dengue surveillance by establishing sentinel sites at health centers and hospitals in the most affected areas of Dire Dawa, Afar and Somali Regions; strengthen capacity for laboratory diagnosis and case management; develop an integrated vector management strategy and plan of action; establish a coordination mechanism with relevant sectors, including establishment of a multi-sectoral task force; work with partners such as WHO, CDC and AFENET for capacity building in case management, integrated vector management and surveillance; actively engage in Advocacy, communication and social mobilization (9).
General Objective
To investigate Dengue fever outbreak and commence outbreak prevention and control measures, in Godey town, Somali Region, Ethiopia July 2015.
Specific Objectives
To describe the magnitude of the outbreak by person, place, and time
To identify risk factors associated with Dengue fever outbreak
To recommend prevention and control measures