Why Tanzania’s dengue spike may have gone unnoticed

Dar es Salaam. The dengue viruses (DENVs) which thrive in Aedes aegypti mosquitoes that are highly prevalent in Tanzania and other parts of the world are continually spreading and causing dengue fever, yet many cases of the disease may have gone unnoticed in the country as attention was turned to  Covid-19 pandemic.
Outbreaks of dengue fever have previously been widely reported especially in the months of March to May in Dar es Salaam, a city that is generally hot and humid with small seasonal and daily variations in temperature. The dengue viruses are known to grow faster and spread in the mosquitoes at higher temperatures.
Yet, according to studies, outbreak of the disease are usually generally underreported , partly because patients tend to exhibit mild symptoms and are often mistaken for malaria.
But a number of them may develop severe dengue and die, as reported in a study, titled: Dengue fever in Dar es Salaam, Tanzania: clinical features and outcome in populations of black and non-black racial category.
Researchers say the outbreaks could easily be detected and reported if heath facilities adopted simple medical tests that can be performed at the bedside (point-of-care tests) instead of relying on medical laboratory testing that entails sending off specimens away from where a patient is being treated and then waiting hours or days for results.
In most urban areas of the country, especially in Dar es Salaam, the risk of being infected with dengue virus remains high, with some residents reporting to have been diagnosed with the disease last week.
However, they are largely unaware they could also be increasingly creating breeding grounds for Aedes aegypti mosquitoes in their homesteads, thus increasing the risk of being infected through bites.
Four out of 10 houses in Dar es Salaam have been found to have water-holding containers that support dengue mosquito breeding in their premises, says a study tilted: Climate Change Influences Potential Distribution of Infected Aedes aegypti Co-Occurrence with Dengue Epidemics Risk Areas in Tanzania.
“Aedes mosquitos breeding is also taking place in flower pots, water troughs, axils of banana, ponds, swamps, coconut shells, water reservoir tanks, ponds, beer or soda crates, sewerage inspection chambers and pits for antenna poles,’’ says Dr Leonard  Mboera, a researcher in Emerging and Vector-borne Diseases at SACIDS Foundation for One Health, located at Sokoine University of Agriculture.
To reduce spread, he suggests, “The motto [for every citizen] should be: “Stop breeding mosquito; dispose unwanted containers appropriately.”

Residents unaware when infected
A month ago when Covid-19 was top in the news, Mr Tom Kagaruki, a resident of Kimara in Dar es Salaam, felt feverish, had night sweats and loss of appetite. However, what came to his mind at the time was a possible coronavirus infection—not malaria, not dengue fever or any other disease. Fearing he could have contracted the coronavirus, he opted for alternative remedies before going for medical checkups.
Few days later, Kagaruki went to Agha Khan Hospital where, after a series of medical tests; doctors diagnosed him with a viral infection whose source they could not explain. “But they said my symptoms didn’t warrant a Covid-19 test,” he tells The Citizen. “They told me the body would fight off the virus,” says Kagaruki, adding: “I eventually got relief after embarking on physical exercising and eating lots of fruits.”

 Symptoms resurface, tests positive for dengue
“This week, I began feeling the same symptoms of headache, fever, sweat, loss of appetite and general malaise. This time it came with bad sleep...I wasn't sleeping well at all,” says Kagaruki who, after a weekend of struggling, he decided to go back to hospital.
“Doctors recommended four tests on blood and urine, but all turned out negative. Later, a second doctor I saw for the day said I had a viral infection and suggested a dengue fever test which came positive. I was told to manage it by curing symptoms such as headaches using panadol. Lots of water and fruits was the advice to regain appetite,” he explains.

Baffled
“My surprise is, where was I bitten by that mosquito [that spreads dengue virus],” queries the 47 year old, unaware that right in his home or work place there could a breeding site for Aedes aegypti mosquitoes that harbor the dengue virus.
Experts also fear that an outbreak of dengue fever could have gone unreported due to overlapping of symptoms between dengue fever and Covid-19. But that is, if heath workers relegated prompt diagnosis of dengue, and if people with fever did not visit health facilities.  
“Efforts against prevention and control of dengue fever might have been  jeopardized as currently everyone is focusing on Covid - 19 hence dengue fever patients may not be detected. During and after rainy season it's when mosquitoes, including Aedes species, do flourish,” says Dr Gordian Kikompolisi, a tropical disease control expert and technical specialist at Abt Associates.
The government has been working on the “Tanzania National Contingency Plan for Prevention and Control of Dengue Fever, May-October 2019” and mid last year, health minister Ummy Mwalimu said efforts were ongoing to control vector-borne diseases, including those attributed to mosquitoes.
There is, however, a pressing need to evaluate how the efforts against vector-borne diseases such malaria and dengue may have been effected, other experts suggest.
“The Minister of Health, in her message on the World Malaria Day stated that we will maintain prevention efforts against malaria so the gains are not lost. I believe this is the case for dengue fever as well,’’ says a mosquito biologist and Director of Science at Ifakara Health Institute Dr Fredros Okumu.
“The full magnitude of these disruptions will be known only after the dust settles, but am optimistic that we can stay vigilant in line with the guidance from the ministry,’’ says Dr Okumu.