Public health nightmare: East Africa put on high alert over dengue fever outbreak

Thursday May 29 2014

Public health officials in East Africa are on high alert as Tanzania battles with an outbreak of the viral disease that has no cure, surveillance on the Indian Ocean coastline has been heightened. TEA Graphic

At the Ubungo bus terminus outside Dar es Salaam’s central business district, a contingent of law enforcers and officials from the Surface and Maritime Transport Agency (Sumatra) swarm on to buses headed out to the countryside.

Armed with knapsack sprayers, the officials get busy fumigating the buses. While this leaves passengers with mixed feelings, especially due to the resultant delays, the exercise is part of a new campaign against dengue fever, that has lately hit the capital city and other parts of the country.

The government has initiated the campaign to kill mosquitoes to stop the spread of the disease to other regions which the buses serve.

Bus operators are not amused, as they have to part with $40 for the compulsory service, but they have been left with no choice, with government data indicating that the disease has claimed three lives and left hundreds hospitalised.

Their licences

The government has warned those defying the directive to have their vehicles fumigated that their licences will be withdrawn.


The Ministry of Health and Social Welfare has distributed dengue rapid diagnostic kits to all public health centres in the country to deal with any emerging cases of the fever.

Across the border in Kenya, researchers at the Kenya Medical Research Institute (Kemri) said on Thursday they had heightened surveillance on the Kenyan Coast and north, which are considered high risk areas.

Such is the level of alertness that the dengue fever outbreak in Tanzania has triggered in East Africa, especially among the countries bordering the Indian Ocean coastline. The viral disease, which has no cure, is posing a public health nightmare in the region.

Official reports from the Tanzanian Health Ministry show that more than 400 patients in Dar es Salaam have been diagnosed with dengue fever over the past four months and three have died.

Dengue fever, which is transmitted by the aedes aegypti mosquito, is common in tropical regions, but scientists believe that climate change is making the mosquitoes more prevalent in the region. Cross-border migrations accelerate transmission of the virus, public health officials say.

Dengue fever is said to affect about 390 million people every year, and is particularly prevalent on the East African coast. Kemri researchers said the disease is a major problem in Kenya, Somalia, Eritrea and Djibouti, which have reported sporadic cases before and are at a high risk of outbreaks.

The World Health Organisation last month issued a global alert on the rise of vector-borne diseases, urging all travellers to take precautions, after it also emerged that 40 per cent of the world’s population is at risk from the dengue virus.

In a message dubbed “Small bite, big threat,” which was part of the campaign to mark the World Health Day, the WHO said: “Mosquito-borne dengue… is now found in 100 countries, putting more than 2.5 billion people — over 40 per cent of the world’s population — at risk.”

This puts dengue fever on the list of what the WHO terms the “diseases you should know before you travel.” The disease has been reported in 22 countries in Africa, but some say it is likely to be present on the entire continent, putting 20 per cent of the population at risk.

In East Africa, strains 1, 2 and 3 of the dengue virus are common causes of acute fever.

Dr Mrisho Lupinda, a medical specialist in Dar es Salaam who has been researching the disease, said: “The climatic situation now favours the multiplication of the aedes aegypti mosquitoes, compared with the past 30 or 40 years.” Dr Lupinda attributed the virus’s spread to free movement of people and cross-border trade.

No cause for alarm

The doctor said that there is no cause for alarm, as 90 per cent of the cases of reported to hospitals are classical — meaning “they only need supportive care by working on their high body temperature and advice on protective measures at home.”

He said only 10 per cent of the cases are dangerous enough to require serious medical attention.

Tanzania has suffered intermittent outbreaks since September last year.

Health officials said the biggest challenge has been the lack of kits to test patients.

President Jakaya Kikwete last week directed the Health and Finance Ministries to order sufficient medical kits for screening dengue and distribute them to health facilities countrywide. The government announced it has committed $41 million to fight the virus, including destroying the breeding grounds for the mosquitoes.

A report published in The Journal of Emerging Infectious Diseases says that the virus could be present in most East African countries.

A lead researcher of the survey, Dr Francesco Vairo from Italy, told a group of scientists at a recent conference organised by the National Institute for Medical Research (NIMR) in Dar es Salaam that dengue poses a threat in Tanzania and could be under-diagnosed because of its resemblance to malaria.

Travellers from Europe

Dr Vairo’s warning affirmed the findings of the survey in Zanzibar and Tanzania Mainland, which showed that travellers from Europe and Japan were found to be infected with DENV-3 — one of the three strains of dengue virus — after a visit to Tanzania Mainland or Zanzibar.

Out of 500 healthy adults who enrolled for the survey at the Zanzibar National Blood Transfusion Services, half were found to harbour strains of the dengue virus in their blood according to the report titled IgG Against Dengue Virus in Healthy Blood Donors, Zanzibar, Tanzania.

Rosemary Sang, head of the arbovirology laboratory of the Centre for Virus Research at Kemri, said that although Kenya has test kits, the most accurate ones used to test both the antibodies and antigens of the virus are expensive and therefore unavailable in public hospitals.

“Kenya uses the rapid test kits, which are not accurate, and therefore some of the tests are confirmed at Kemri, where the accurate test kits — the enzyme-linked immunosorbent assay (ELISA) for testing the antibodies and the polymerase chain reaction (PCR) kit for testing the antigens) — are available.

The disease outbreaks, she said, are increasing and are projected to further increase over the coming years due to global warming, which expands the habitat of the mosquitoes.

In East Africa, only Kenya and Tanzania have suffered outbreaks of the disease. There have been more than 100 cases on the Kenya Coast since last year, and an outbreak in Mandera in northeastern Kenya in 2011 affected about 5,000 people.

John Odondi, Director of Primary Health Care at Kenya’s Ministry of Health, said the government is aware of the outbreaks and is working with Kemri to increase surveillance in these areas and create awareness about the disease.

But Dr Sang said Kenya had not suffered a dengue fever outbreak between 1992 and 2011.

In 1992, she said the outbreak was a spillover from the Seychelles and in 2011, the Mandera outbreak was a spillover from Somalia, due to the movement of people when the Kenya Defence Forces soldiers entered southern Somalia to fight the Al Shabaab militants.

The dengue virus is said to have originated from Asia, which still suffers more outbreaks than Africa.

The dengue emerged during the Second World War and has become increasingly important, with progressively longer and more frequent cyclical epidemics being reported.

“The virus thrives well in places where there is more heat and the sanitation is poor. The weather conditions in Asian countries are the same as the East African coastal areas,” Dr Sang said, adding that people should take precautions when travelling from the non-endemic regions to the high endemic regions.

WHO says 3 billion people live in regions susceptible to dengue and that figure includes 600 million people who live in Southeast Asia, where the disease is prevalent. Indonesia, was ranked first in the number of dengue cases in the region, with more than 90,000 cases in 2013.

Vietnam and Cambodia, with substantially smaller populations, ranked second and third, with 86,000 and 42,000 cases respectively.

WHO has labelled dengue as one of the fastest growing viral threats globally.

The East African region has experienced several deadly fever outbreaks, including Ebola, hepatitis and Marburg.

Uganda has experienced the deadly haemorrhagic fevers because, according to experts, it is located in a hotspot for killer viruses believed to originate from the neighbouring DR Congo.

Researchers are yet to record the effects of the Ebola/Marburg vaccine on humans.

WHO reports indicate that dengue fever transmission in recent years has increased predominantly in urban and semi-urban areas and has become a major international public health concern.

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Dr Sang said scientists have not developed an effective vaccine to prevent dengue fever but studies are ongoing.

“The dengue virus has four confirmed types, and it is hard to develop a vaccine that can eradicate all four.”

The best preventive measure for residents living in areas infested with aedes aegypti mosquitoes is to eliminate their breeding areas.

“Items that collect rainwater or store water, such as garbage cans, house gutters and buckets, should be covered or properly disposed of,” said Dr Sang.

“Also, maintain swimming pools in good condition and appropriately chlorinated and empty plastic swimming pools when not in use.”

Dr Sang said people living on the Coast and areas where the outbreaks have been reported in the past should ensure that all water containers are well covered and use mosquito repellents both during the day and at night to avoid transmission.

“At the Coast, and where people do not have running water, the mosquitoes that carry the virus hide and breed fast in uncovered plastic containers that are used for water storage,” said Dr Sang, adding, “The aedes aegypti mosquitoes that carry the virus bite people during the day because the high temperatures of the day help the virus to grow rapidly.”

Studies are ongoing

“We have a surveillance programme in place studying the dengue virus vectors,” said Dr Sang, adding that several studies are ongoing at the Kemri to understand why the mosquitos breed more in coastal areas.

“We are also conducting research on different mosquito populations to see whether they are susceptible to dengue virus.”

Tanzanian experts on vector-borne diseases from the National Institute for Medical Research and Muhimbili University of Health and Allied Sciences are carrying out surveillance in the city’s municipalities alongside sensitisation campaigns for the public.

Many people, especially children and teens, may experience no signs or symptoms during a mild case of dengue fever.

The symptoms occur four to 10 days after the person has been bitten by an infected mosquito.

The symptoms are similar to those of malaria and generally, young children and those on their first dengue infection have a milder illness than older children and adults.
The most noted symptoms are high fever, severe headaches, muscle, bone and joint pain and pain behind the eyes.

Patients may also experience a rash, nausea and vomiting, and minor bleeding from gums or the nose.

Damaged and leaky

“Most people recover within a week or so,” said Dr Sang. “In some cases, however, symptoms worsen and can become life-threatening. Blood vessels often become damaged and leaky, and the number of clot-forming cells in your bloodstream falls.”

WHO recommends that people who have dengue fever rest, drink plenty of fluids to prevent dehydration, avoid mosquito bites while febrile and reduce the fever using paracetamol or see a doctor.

But WHO says that other pain killers such as Ibuprofen and Diclofenac are not recommended as they can increase bleeding due to low platelet (blood clotting cells) count.

“Those flu-like symptoms also hamper public health officials’ ability to track the disease, because official surveillance of occurrences is based on medical reports, and patients may not seek care for what they assume is a bout of flu,” said Dr Sang.

WHO says that an estimated 50 million to 100 million dengue infections occur worldwide yearly, and severe forms of the disease can be fatal, especially among children.

Last year, Australian scientists claimed that they had developed the world’s first cure for dengue fever jointly with Indonesian scientists, but it is yet to be approved by WHO.

READ: World’s first cure for dengue fever

The scientists say the 98alive drug kills all the four strains of the virus.

Southeast Asian countries reports on dengue fever last year heightened efforts this year to control the aedes aegypti mosquito.

“Without a preventive vaccine or cure, these measures and rigorous public-awareness campaigns are the only tools to combat dengue,” said Dr Sang.

Economic burden

Beyond dengue’s death toll, its impact is largely felt in economic terms because sick people cannot work or attend school. 

The Schneider Institutes for Health Policy at Brandeis University in the US estimated in February that the annual economic burden of dengue in Southeast Asia is nearly $1 billion, with Indonesia and Thailand experiencing the highest costs.

By Christabel Ligami and Syriacus Buguzi