Reports & Analysis | Infectious Diseases | Summary
Surveillance of viral haemorrhagic fevers, Rift Valley fever and yellow fever in humans, South Africa, 2019-2023
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Estimated Listening Time: 7 minutes, 21 seconds
Originally Published: May 2023
Source: Public Health Bulletin
Type of article: Summary of Report or Analysis
MedED Catalogue Reference: MDRA001
Category: Reports & Analysis
Cross-reference: Infectious Diseases
Keywords: Lassa Fever, Rift Valley Fever, Haemorrhagic Fever, Crimean-Congo Hemorrhagic Fever, Ebola
Key takeaway
While locally acquired Crimean-Congo Hemorrhagic Fever and Rift Valley Fever are rare, and the risk of non-endemic viral hemorrhagic fevers is low, maintaining and enhancing surveillance and response mechanisms is crucial to ensure prompt detection and timely public health responses.
Report Overview & Importance | Abbreviations | The Context | Study Design | Findings | Summary | Access the Report
Report Overview & Importance
The National Institute for Communicable Diseases has released its Surveillance Report of viral haemorrhagic fevers, Rift Valley fever and yellow fever in humans for the period 2019 – 2023.
Detecting and responding to cases of viral hemorrhagic fever (VHF) is crucial for South Africa and is in accordance with International Health Regulations and the Global Health Security Agenda.
VHF, Rift Valley fever (RVF), and yellow fever (YF) pose risks to international travel and trade due to their potential to spread across borders. While South Africa has experienced few reports of Ebola virus disease (EVD), Marburg virus disease (MVD), Lassa fever (LF), and Lujo fever, recent outbreaks in neighbouring regions increase the risk of importation.
In addition, changing vector ecology due to climate change and land use impacts the epidemiology of these diseases. Currently, in South Africa, surveillance for VHF, RVF, and YF relies on passive methods, with clinical diagnoses confirmed by laboratory testing and reported through the National Notifiable Medical Conditions platform.
When taken in this context, and given that vaccines and treatments for most of these diseases are lacking, there is an urgent need to increase and improve surveillance methods and response capability to contain possible outbreaks.
Below is a summary of the findings in the report.
The Context
LF is the most commonly reported viral hemorrhagic fever (VHF) among travellers worldwide.
- Cases in South Africa are rare and typically confined to travellers returning from endemic regions.
- The first case of LF occurred in 2007 in a physician who had travelled extensively for a polio vaccination campaign in Nigeria, contracted LF and was evacuated to South Africa for treatment.
- Similarly, the 2022 case involved a patient who had recently visited Nigeria. Both cases resulted in fatalities. LF is the most commonly reported viral hemorrhagic fever (VHF) among travellers worldwide.
Crimean-Congo Hemorrhagic Fever (CCHF) has been endemic in South Africa since 1981, with sporadic cases reported across all provinces, particularly in the Northern Cape, Free State, and North West.
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Over two-thirds of cases involved tick exposure, while others reported contact with animal tissues or blood or lived and worked in rural areas prone to tick exposure.
- South Africa has only experienced one confirmed case of imported EVD, linked to secondary transmission within the country.
In 1975, MVD was reported in a tourist who had travelled extensively in both Zimbabwe and South Africa, although the source of his exposure remains speculative.
Lujo fever was identified in a fatal outbreak among healthcare workers in Johannesburg in 2008.
Rift Valley fever outbreaks occur periodically, with the most recent in 2018 involving four cases in farm workers.
No cases of yellow fever have been confirmed in South Africa to date.
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Study Design
This report is a retrospective review of suspected or confirmed cases of VHF, RVF and YF occurring in South Africa, which were documented during the period 1 January 2019 to 31 December 2023.
The reviewed cases encompassed those submitted for investigation of viral hemorrhagic fevers, including EVD, MVD, LF, Lujo fever, VHF associated with New World arenavirus infections, CCHF or newly identified viruses causing haemorrhagic fever, Rift Valley fever (RVF), and yellow fever (YF).
The cases were documented by the Special Viral Pathogens Laboratory and the Arbovirus Reference Laboratory, situated within the Centre for Emerging Zoonotic and Parasitic Diseases at the National Institute of Communicable Diseases and National Health Laboratory Services.
Included in the review were case submission forms, case investigation forms, and unstructured case notes obtained from referring physicians, medical officers managing the NICD hotline, laboratory personnel involved in investigations, as well as district and provincial Department of Health investigation teams.
Laboratory-confirmed cases were categorized as those testing positive by reverse transcription polymerase chain reaction (RT-PCR), showing positivity for anti-virus immunoglobulin M (IgM), or demonstrating seroconversion through a four-fold increase in anti-virus immunoglobulin G (IgG) titer across serially collected blood samples.
A total of 232 cases were investigated during the reporting period. Of these, the endemic diseases of CCHF and RFV were the most frequent (77 and 90 cases, respectively).
Of the investigated cases, 11 cases were confirmed. These cases were as follows:
One case of Lassa Fever was confirmed, which proved fatal (2022).
- The patient had a history of extensive travel in Nigeria and had recently returned home. Given that LF has an incubation period of between 2 and 21 days, it is probable the patient had been exposed to the virus in that country.
Ten cases of CCHF were reported during the period, with one fatality noted.
- Three cases were located in the North West Province, three in the Western Cape, two in the Free State, one in the Eastern Cape, and one in the Northern Cape.
- Tick bites were identified as the predominant cause for the confirmed cases, accounting for seven instances.
- Occupational exposure to ticks was prevalent in these cases, with four cases linked to livestock farming, one case associated with veterinary work, and another related to game management activities, such as culling.
- One case involved a hiker who reported a tick bite.
- An individual working in an abattoir may have been exposed to ticks or had contact with blood and tissues from animals carrying the virus.
No other cases of VHF, RVF, YF, or haemorrhagic fever associated with newly identified viruses occurred during the period under review.
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While the likelihood of non-endemic viral hemorrhagic fevers (VHF), Rift Valley fever (RVF), and yellow fever (YF) entering South Africa is minimal, and instances of locally acquired Crimean-Congo Hemorrhagic Fever (CCHF) and RVF are rare, enhanced and cohesive surveillance and response systems are vital. These measures are essential for promptly identifying imported cases and implementing effective public health interventions, particularly to mitigate potential outbreaks.
Summary Page: Surveillance of Viral Hemorrhagic Fevers in South Africa (2019-2023)- Summary Page
Report Download: Surveillance of viral haemorrhagic fevers, Rift Valley fever and yellow fever in humans, South Africa, 2019-2023 (PDF)
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