Laboratory sequencing confirmed the presence of PHV genetic material in the sampled sardines. Officials noted it was found in dead fish and, at lower levels, in some apparently healthy individuals collected from the West Coast. This has deepened the investigative focus rather than providing a simple answer.
Link to Australia and New Zealand events
PHV was associated with two large-scale sardine/pilchard mortality events in Australasia during the 1990s. The most notable began in 1995 in South Australia, spread across a large portion of the Australian pilchard range (thousands of kilometres of coastline), and reached New Zealand. Affected fish showed rapid onset of respiratory distress, with death linked to gill lesions (inflammation progressing to epithelial hypertrophy and hyperplasia). A herpesvirus was consistently found in the gills of affected fish and proposed as the aetiological agent; the mortality front advanced at roughly 30 km per day in ways that suggested involvement of a vector beyond simple fish migration or currents.
Later, the virus was detected in apparently healthy Australian populations without continuous large-scale mortality. PHV had not previously been reported in South African sardines prior to the 2026 findings.
Current assessment of cause in South Africa
DFFE and scientists have been careful to state that the presence of PHV does not automatically establish it as the cause of the deaths. Key points from official updates include:
- Detection in some apparently healthy fish suggests the virus alone may not be sufficient to trigger mass mortality.
- Other potential contributing or triggering factors under active investigation include environmental stressors such as harmful algal blooms, low dissolved oxygen, or unusual oceanographic conditions (e.g., enhanced upwelling, unusually cold nearshore water, or low-oxygen conditions noted in areas like St Helena Bay prior to the event).
- Tests for toxins associated with a harmful algal bloom (involving Alexandrium catenella that was present in Saldanha Bay at the outset) found none of the relevant paralytic toxins in the key sardine samples examined. Low levels of other compounds (such as domoic acid or yessotoxin in some reporting) have been noted but are not viewed as the primary driver.
The investigation remains multi-faceted, involving the Department, research institutions (including disease testing by bodies such as the South African Institute for Aquatic Biodiversity and Rhodes University), specialist laboratories, the fishing industry, and collaborating scientists. Expanded surveillance along West, South, and East coasts is underway, and the routine hydroacoustic biomass survey (typically October–November) is expected to help assess any broader population-level impact. A task team involving government, industry, and other parties is being established, with stakeholder briefings planned.
Public health, food safety, and practical advice
PHV is described as a virus associated with sardines/pilchards. There is currently no evidence that it infects people or other animals. Officials have stated that the finding does not indicate that healthy sardines caught commercially or canned products are unsafe, and it does not currently justify a general suspension of fishing or canning. West Coast canneries have continued to accept healthy sardines from areas north of St Helena Bay in some reporting, while some processors in affected zones paused pending further results.
The public has been advised to avoid collecting or consuming dead or dying fish, and to keep pets away from them. This is standard precautionary guidance during unexplained or pathogen-associated die-offs.
Broader context and implications
South African sardine stocks support an important small-pelagic fishery and form a key part of the marine food web (including for predators). Mass mortality events can have ecological and economic ripple effects, though the scale of biomass impact from this specific event is still being assessed. Historical Australian experience shows that such viruses can become detectable in populations without perpetual mass die-offs, often interacting with environmental stressors.
Similar complexities appear in other marine mortality investigations worldwide: pathogens, water quality, temperature/oxygen anomalies, algal toxins, and oceanographic shifts frequently interact, making single-cause attributions rare. The South African response emphasizes ongoing testing, multi-factor analysis, industry engagement, and transparent updates rather than premature conclusions or broad restrictions.
In short, the detection of PHV in every South African sardine sample tested to date is a significant new finding given the virus’s history in Australasia, but scientists stress it is one piece of a larger puzzle. Environmental co-factors remain under close scrutiny, food safety for healthy commercial product is not currently flagged as a concern, and the investigation continues. For the latest official details, primary sources are DFFE media statements.
