Onslaught of Dengue Fever Outbreak

An outbreak of dengue fever has been reported in Mombasa since the beginning of this year. Dengue fever is an acute febrile illness caused by any one of four distinct but closely related dengue virus serotypes. Dengue viruses are arboviruses (arthropod-borne virus) that are transmitted primarily between humans through the bite of an infected mosquito of the Aedes aegypti or Aedes albopictus species. Dengue is the world’s most common mosquito-borne viral disease and a leading cause of morbidity throughout the tropics and subtropics  illness caused by one of the four DENV types can range from a non specific acute febrile illness to severe disease with shock, hemorrhage, and multi-organ impairment. There is no vaccine, chemoprophylaxis or antiviral medication to treat patients with dengue and treatment is mainly supportive.

This is the first reported dengue outbreak in Mombasa since 1982. However, a dengue outbreak occurred in Kenya in Mandera East district in 2011 and 2013, affecting approximately 1300 and 190 people respectively. The outbreak in Mandera East in September 2011 was most likely a spread from Somalia where the outbreak had been reported earlier among the AMISOM (African Mission in Somalia) soldiers several months prior to the Kenyan outbreak. The outbreak occurred again this year in January but has since been controlled.

It is not clear yet as to the origin of the current outbreak in Mombasa as the index case has not been traced with certainty. Although the first laboratory confirmed case was reported by Kenya Medical Research Institute (KEMRI) on 7th March 2013, a retrospective review of hospital records indicate that the first case was confirmed in a private laboratory on 7th January 2013. From this review, there were at least 3 cases in January and 2 cases in February that had been confirmed in private laboratories. Since there was an ongoing outbreak in Mandera in early January 2013, it is possible that the index case in Mombasa could have travelled to Mandera and gotten infected there.

As of 26th April 2013, 83 of 148 (56%) blood samples collected from residents of Mombasa who visited health facilities with dengue-like illness have tested positive for dengue virus (DENV) infection by RT-PCR. Identified DENV serotypes include DENV-1 (69%), DENV-2 (28%), and DENV-3 (3%); at least one sample was positive for 2 DENV serotypes (DENV-1 and 2). Age range for confirmed cases was 4 to 62 years old with a median of 34; 56% were male. Cases have been reported from most villages/estates in Mombasa with majority of the cases having been reported by private hospitals (Aga Khan Hospital 36%, Mombasa Hospital 30%, and Pandya Hospital 26%). No dengue associated deaths have been reported to-date.

As a response to controlling the outbreak, the Ministry of Health has embarked on a number of activities. A team from the Division of Disease Surveillance and Response (DDSR), Field Epidemiology and Laboratory Training Program (FELTP), KEMRI and local staff from the Ministry of Health are responding to this outbreak with in-country technical support and assistance from US Centers for Disease Control and Prevention in Kenya (CDC-Kenya) and the US Army Medical Research Unit-Kenya (USAMRU-K). Among the response measures being conducted by this team include sensitization of health workers and community members, active case search, and vector control.

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