Molecular Characterization and Phylogenetic Analysis of Dengue Fever Viruses in Three Outbreaks in Tanzania Between 2017 and 2019.

BACKGROUND: Dengue is a disease of public health interest, and Tanzania experienced major outbreaks in 2014 and 2019. Here, we report our findings on the molecular characterization of dengue viruses (DENV) that circulated during two smaller outbreaks (2017 and 2018) and one major epidemic (2019) in Tanzania. METHODOLOGY/PRINCIPAL FINDINGS: We tested archived serum samples from 1,381 suspected dengue fever patients, with a median age of 29 (IQR:22-40) years, referred to the National Public Health Laboratory for confirmation of DENV infection. DENV serotypes were identified by reverse transcription polymerase chain reaction (RT-PCR), and specific genotypes were identified by sequencing the envelope glycoprotein gene and phylogenetic inference methods. DENV was confirmed in 823 (59.6%) cases. More than half (54.7%) of patients with dengue fever infection were males, and nearly three-quarters (73%) of the infected individuals were living in Kinondoni district, Dar es Salaam. DENV-3 Genotype III caused the two smaller outbreaks in 2017 and 2018, while DENV-1 Genotype V caused the 2019 epidemic. DENV-1 Genotype I was also detected in one patient in 2019. CONCLUSION/SIGNIFICANCE: This study has demonstrated the molecular diversity of dengue viruses circulating in Tanzania. We found that contemporary circulating serotypes did not cause the major epidemic of 2019 but rather due to a serotype shift from DENV-3 (2017/2018) to DENV-1 in 2019. Such a change increases the risk for patients previously infected with a particular serotype to develop severe symptoms upon potential re-infection with a heterologous serotype due to antibody-dependent enhancement of infection. Therefore, the circulation of serotypes emphasizes the need to strengthen the country's dengue surveillance system for better management of patients, early detection of outbreaks, and vaccine development.

Preliminary investigation and intervention of the suspected plague outbreak in Madunga, Babati District-Tanzania.

BACKGROUND: Rodents are known to be reservoirs of plague bacteria, Yesinia pestis in the sylvatic cycle. A preliminary investigation of the suspected plague outbreak was conducted in Madunga Ward, Babati District Council in Manyara Region December-2019-January 2020 Following reported two cases which were clinically suspected as showing plague disease symptoms. METHOD: The commensal and field rodents were live trapped using Sherman traps in Madunga Ward, where plague suspect cases were reported and, in the Nou-forest reserve areas at Madunga Ward, Babati District Council, to assess plague risk in the area. Fleas were collected inside the houses using light traps and on the rodents 'body after anaesthetizing the captured rodent to determine flea indices which are used to estimate the risk of plague transmission. Lung impression smears were made from sacrificed rodents to examine for possible bipolar stained Yersinia spp bacilli. RESULTS: A total of 86 rodents consisting of ten rodent species were captured and identified from the study sites. Nine forest rodent species were collected. Field/fallow rodent species were dominated by Mastomys natalensis. whereas domestic rodent species captured was Rattus rattus. Overall lung impression smear showed bipolar stain were 14 (16.28%) while House Flea Index (HFI) was 3.1 and Rodent Flea Index (RFI) was 1.8. CONCLUSION: The findings of this study have shown that, the presence of bipolar stained bacilli in lung impression smears of captured species of rodents indicates (not confirmed) possible circulation of Yesrsinia pests in rodents and the high flea indices in the area which included the most common flea species known to be plague vectors in Tanzania could have played transmission role in this suspected outbreak. The study recommends surveillance follow-up in the area and subject collected samples to the standard plague confirmatory diagnosis.

The Tanzania Field Epidemiology and Laboratory Training Program: building and transforming the public health workforce.

The Tanzania Field Epidemiology and Laboratory Training Program (TFELTP) was established in 2008 as a partnership among the Ministry of Health and Social Welfare (MOHSW), Muhimbili University of Health and Allied Sciences, National Institute for Medical Research, and local and international partners. TFELTP was established to strengthen the capacity of MOHSW to conduct public health surveillance and response, manage national disease control and prevention programs, and to enhance public health laboratory support for surveillance, diagnosis, treatment and disease monitoring. TFELTP is a 2-year full-time training program with approximately 25% time spent in class, and 75% in the field. TFELTP offers two tracks leading to an MSc degree in either Applied Epidemiology or, Epidemiology and Laboratory Management. Since 2008, the program has enrolled a total of 33 trainees (23 males, 10 females). Of these, 11 were enrolled in 2008 and 100% graduated in 2010. All 11 graduates of cohort 1 are currently employed in public health positions within the country. Demand for the program as measured by the number of applicants has grown from 28 in 2008 to 56 in 2011. While training the public health leaders of the country, TFELTP has also provided essential service to the country in responding to high-profile disease outbreaks, and evaluating and improving its public health surveillance systems and diseases control programs. TFELTP was involved in the country assessment of the revised International Health Regulations (IHR) core capabilities, development of the Tanzania IHR plan, and incorporation of IHR into the revised Tanzania Integrated Disease Surveillance and Response (IDSR) guidelines. TFELTP is training a competent core group of public health leaders for Tanzania, as well as providing much needed service to the MOHSW in the areas of routine surveillance, outbreak detection and response, and disease program management. However, the immediate challenges that the program must address include development of a full range of in-country teaching capacity for the program, as well as a career path for graduates.

Epidemiologic and clinical aspects of a Rift Valley fever outbreak in humans in Tanzania, 2007.

In January 2007, an outbreak of Rift Valley fever (RVF) was detected among humans in northern Tanzania districts. By the end of the outbreak in June, 2007, 511 suspect RVF cases had been recorded from 10 of the 21 regions of Tanzania, with laboratory confirmation of 186 cases and another 123 probable cases. All confirmed RVF cases were located in the north-central and southern regions of the country, with an eventual fatality rate of 28.2% (N = 144). All suspected cases had fever; 89% had encephalopathy, 10% hemorrhage, and 3% retinopathy. A total of 169 (55%) of the 309 confirmed or probable cases were also positive for malaria as detected by peripheral blood smear. In a cohort of 20 RVF cases with known outcome that were also positive for human immunodeficiency virus, 15 (75%) died. Contact with sick animals and animal products, including blood, meat, and milk, were identified as major risk factors of acquiring RVF.

Pathologic studies on suspect animal and human cases of Rift Valley fever from an outbreak in Eastern Africa, 2006-2007.

Rift Valley fever (RVF) is an important viral zoonotic disease in Africa with periodic outbreaks associated with severe disease, death, and economic hardship. During the 2006-2007 outbreaks in Eastern Africa, postmortem and necropsy tissue samples from 14 animals and 20 humans clinically suspected of RVF were studied with histopathologic evaluation and immunohistochemical (IHC) assays. Six animal and 11 human samples had IHC evidence of Rift Valley fever virus (RVFV) antigens. We found that extensive hepatocellular necrosis without prominent inflammatory cell infiltrates is the most distinctive histopathologic change in liver tissues infected with RVFV. Pathologic studies on postmortem tissue samples can help establish the diagnosis of RVF, differentiating from endemic diseases with clinical manifestations similar to RVF, such as malaria, leptospirosis, or yellow fever.