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.

Introduction: In March 2023, a Marburg Virus Disease (MVD) outbreak was declared in Kagera region, Northwestern Tanzania. This was the first MVD outbreak in the country. We describe the epidemiological characteristics of MVD cases and contacts. Methods: The Ministry of Health activated an outbreak response team. Outbreak investigation methods were applied to cases identified through MVD standard case definitions and confirmed through reverse-transcriptase polymerase chain reaction (RT PCR). All identified case contacts were added into the contact listing form and followed up in-person daily for any signs or symptoms for 21 days. Data collected from various forms was managed and analyzed using Excel and QGIS software for mapping. Results: A total of nine MVD cases were reported with eight laboratory-confirmed and one probable. Two of the reported cases were frontline healthcare workers and seven were family related members. Cases were children and adults between 1–59 years of age with a median age of 34 years. Six were males. Six cases died equivalent to a case fatality rate (CFR) of 66.7%. A total of 212 individuals were identified as contacts and two (2) became cases. The outbreak was localized in two geo-administrative wards (Maruku and Kanyangereko) of Bukoba District Council. Conclusion: Transmission during this outbreak occurred among family members and healthcare workers who provided care to the cases. The delay in detection aggravated the spread and possibly the consequent fatality but once confirmed the swift response stemmed further transmission containing the disease at the epicenter wards. The outbreak lasted for 72 days but as the origin is still unknown, further research is required to explore the source of this outbreak.

We describe the deployment of a custom-designed molecular diagnostic TaqMan Array Card (TAC) to screen for 31 bacterial, protozoal, and viral etiologies in blood from outbreaks of acute febrile illness in Tanzania during 2015–2017. On outbreaks notified to the Tanzanian Ministry of Health, epidemiologists were dispatched and specimens were collected, transported to a central national laboratory, and tested by TAC within 2 days. This algorithm streamlined investigation, diagnosed a typhoid outbreak, and excluded dozens of other etiologies. This method is usable in-country and may be incorporated into algorithms for diagnosing outbreaks.

Viral Haemorrhagic Fever Outbreak presents a significant public health threat, requiring a timely, robust, and well-coordinated response. This paper aims to describe the roles of the Tanzania Field Epidemiology and Laboratory Training Program (TFELTP) graduates and residents in responding to Tanzania’s first Marburg Viral Disease (MVD) outbreak. We performed a secondary data analysis using a range of documents, such as rosters of deployed responders and the TFELTP graduate and resident database, to count and describe them. Additionally, we conducted an exploratory textual analysis of field deployment reports and outbreak situational reports to delineate the roles played by the residents and graduates within each response pillar. A total of 70 TFELTP graduates and residents from different regions were involved in supporting the response efforts. TFELTP graduates and residents actively participated in several interventions, including contact tracing and follow up, sensitising clinicians on surveillance tools such as standard case definitions, alert management, supporting the National and Kagera Regional Public Health Emergency Operations Centres, active case search, risk communication, and community engagement, coordination of logistics, passenger screening at points of entry, and conducting Infection Prevention and Control (IPC) assessments and orientations in 144 Health Facilities. The successes achieved and lessons learned from the MVD response lay a foundation for sustained investment in skilled workforce development. FELTP Training is a key strategy for enhancing global health security and strengthening outbreak response capabilities in Tanzania and beyond.

Respiratory pathogens are significant causes of morbidity and mortality worldwide. Since the emergence of SARS-CoV-2 in 2019 and the mitigation measures implemented to control the pandemic, other respiratory viruses’ transmission and circulation patterns were substantially disrupted. We leveraged the influenza hospitalization surveillance in Tanzania to understand the distribution of respiratory viruses shortly after nonpharmaceutical interventions (NPIs) were lifted. A total of 475 samples that tested negative for SARS-CoV-2 and influenza from March through May 2022 were included in this study. The samples were tested for 16 virus targets using Anyplex II RV16 multiplex assays. The findings indicate that most hospitalizations (74%) were among children under 15 years, with human bocavirus (HBoV) being the most prevalent (26.8%), followed by rhinovirus (RV, 12.3%), parainfluenza viruses (PIVs1–4, 10.2%), respiratory syncytial virus (RSV, 8.7%), adenovirus (AdV, 4.3%), and metapneumovirus (MPV, 2.9%). Notably, 54% of respiratory hospitalizations had no viruses detected. The findings highlight the broad circulation of respiratory viruses shortly after NPIs were lifted in Tanzania. Surveillance for respiratory pathogens beyond influenza and SARS-CoV-2 can inform public health officials of emerging threats in the country and should be considered an important pandemic preparedness measure at a global level.

Globally, 24 measles virus genotypes have been detected, and these genotypes have been classified into eight clades based on 450 nucleotides of the C-terminal region of the nucleoprotein gene. Genotype B3 is predominant in Africa, but there are limited data from Tanzania since the introduction of the second dose of measles-containing vaccine in 2014. A total of 129 nasopharyngeal samples and corresponding sera were collected during measles outbreaks between 2022 and 2024. Viral RNA was extracted from nasopharyngeal swabs prior to RT-qPCR and sequencing of a 450-nucleotide segment of the nucleoprotein (N) gene. Out of 129 nasopharyngeal samples, 73 (56%) were successfully amplified and identified as endemic measles virus genotype B3. Nine distinct sequence identifiers were detected, with seven reported for the first time in the MeaNS database. All the Tanzanian B3 sequences were closely related and clustered with genotype B3, similar to those reported from Kenya, Ethiopia, Rwanda, Uganda, Burundi, and South Africa. On multivariate analysis, only inpatient admission status (p = 0.014) and positive measles IgM (p = 0.003) were found to be associated with positive measles RT-qPCR. Our results indicate that genotype B3 remains endemic in Tanzania and is closely related to other genotype B3 reported globally, indicating its high stability and transmissibility.