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. 2025 Jul 19;17(7):1015.
doi: 10.3390/v17071015.

Rift Valley Fever Outbreak Investigation Associated with a Dairy Farm Abortion Storm, Mbarara District, Western Uganda, 2023

Luke Nyakarahuka  1   2 , Shannon Whitmer  3 , Sophia Mulei  1 , Joanita Mutesi  1 , Jimmy Baluku  1 , Jackson Kyondo  1 , Amy Whitesell  3 , Carson Telford  3 , Alex Tumusiime  1 , Calvin Richie Torach  1 , Dianah Namanya  1 , Mariam Nambuya  4 , Dominic Muhereza  5 , Zainah Kabami  6 , Annet Nankya  6 , David Muwanguzi  4 , Francis Mugabi  5 , Nelson Wandera  5 , Rose Muhindo  7 , Joel M Montgomery  3 , Julius J Lutwama  1 , Stephen Karabyo Balinandi  1 , John D Klena  3 , Trevor R Shoemaker  3
Affiliations

Rift Valley Fever Outbreak Investigation Associated with a Dairy Farm Abortion Storm, Mbarara District, Western Uganda, 2023

Luke Nyakarahuka et al. Viruses. .

Abstract

In Africa, Rift Valley Fever poses a substantial risk to animal health, and human cases occur after contact with infected animals or their tissues. RVF has re-emerged in Uganda after nearly five decades, with multiple outbreaks recorded since 2016. We investigated a unique RVF outbreak associated with an animal abortion storm of 30 events and human cases on a dairy farm in Mbarara District, Western Uganda, in February 2023. Genomic analysis was performed, comparing animal and human RVF viruses (RVFV) circulating in the region. A cluster of thirteen human RVF cases and nine PCR-positive animals could directly be linked with the abortion storm. Overall, during the year 2023, we confirmed 61 human RVFV cases across Uganda, 88.5% of which were reported to have had direct contact with livestock, and a high case fatality rate of 31%. We recommend implementing extensive health education programs in affected communities and using sustainable mosquito control strategies to limit transmission in livestock, coupled with initiating animal vaccination trials in Uganda.

Keywords: RVF virus; Rift Valley Fever; animal abortion storms; human RVF outbreak; livestock–human interface; vaccination trials; western Uganda; zoonotic transmission.

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Conflict of interest statement

The authors declare no conflicts of interest. The funders had no role in the design of this study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
A map of Uganda showing the location of the 2023 Mbarara RVF outbreak and laboratory-confirmed relative to historic RVFV cases.
Figure 2
Figure 2
Epidemic curve of laboratory-confirmed human RVF cases in Uganda from September 2022 to August 2023.
Figure 3
Figure 3
Phylogenetic analysis of the L segment of the Rift Valley Fever virus sequences in Uganda across different time frames (1944–2023). Sequences collected from Uganda are labeled, with sequence names color-coded by their collection timeframe. Blue shading highlights RVFV sequences collected from cattle. Notably, sequences from humans and cattle during the Mbarara outbreak and surrounding regions were closely related, suggesting zoonotic transmission. Bootstrap support values greater than 70% are labeled in red at internal nodes. Major clades are labeled according to Grobbalaar et al. (2011) [12] and Samy et al. (2017) [13], and the scale bar is in units of substitutions/site.
See this image and copyright information in PMC

References

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