Frequently Asked Questions - POMS

​​​​​​​​​​​​​​​What is ​​POMS?

POMS is an acronym for Pacific Oyster Mortality Syndrome, which is a disease caused by the virus Ostreid Herpesvirus-1 (OsHV-1). This virus affects Pacific Oysters (Crassostrea gigas), causing large mortality events (deaths) among farmed oysters. As of 2023, this virus is not known to affect native oyster species in Australia, including the Angasi (flat) oyster and the Sydney Rock oyster.

The acronym POMS and the virus OsHV-1 are often used interchangeably, but POMS refers to the disease event and OsHV-1 refers to the pathogen responsible. ​​

Is it safe to e​​at farmed oysters?​

Oysters sold through retail outlets remain safe to eat. Ostreid herpesvirus-1 does not pose a human health risk, and areas classified as POMS affected or POMS intermediate do not pose a direct human health risk. Please be aware, the Tasmania Department of Health has instructed the public to not collect and eat wild shellfish. ​

When was POMS first detected?

In summer of 2016, an oyster lease in Pitt Water estuary, located in southeast Tasmania, observed unusually high mortality rates among their oyster stock. Oysters were submitted to the Animal Health Laboratory and laboratory results confirmed the presence of Ostreid Herpesvirus-1 (OsHV-1), the virus responsible for POMS. Further surveillance was performed throughout the state to determine which bays are affected by POMS. Testing found the OsHV-1 virus is present in several bays around Tasmania. 

All oyster growing regions throughout Tasmania have been assessed and categorised into different POMS zones for the purpose of movement restrictions relating to oysters and oyster growing equipment. These bays have been assigned different area classifications, or POMS zones, which are designated according to the level of risk that the OsHV-1 virus is present.

​​How does P​​OMS kill Pacific oysters?

POMS is a complex disease and multiple factors need to be present at the same time to cause a large mortality (death) event. These factors include the presence of pacific oysters, the presence of the Ostreid Herpesvirus-1 (OsHV-1), and environmental stresses including rapidly increasing or decreasing temperatures, changes in oyster nutrition, and oyster cultivation activities including oyster grading.

The OsHV-1 virus can remain dormant and present in apparently healthy oysters. POMS mortality events are commonly observed during summer, when water temperatures exceed 16°C. POMS events can result in a 100% mortality rate among farmed oysters. The virus is thought to affect the oyster’s immune system and digestion system, resulting in large mortality rates. 

Where did the​​ virus come from?

The first detection of a POMS outbreak occurred in New South Wales in 2021. It is unknown how the POMS virus entered Australian waters. OsHV-1 virus has been detected in pacific oysters and other shellfish throughout the globe including the America’s, eastern Asia, Oceania and western Europe. Navigate to the Mollusc section by​ ​clicking here: Declared Pests & Diseases.​​

Are other ​​animals affected?

In Australia, POMS is only known to affect pacific oysters. In other parts of the globe, POMS has cause large mortality events in other shellfish including clams, scallops, as well as other oyster species. POMS is not known to affect Angasi or Sydney Rock oysters. 

What is Biosecurit​​y Tasmania doing to limit the spread of the disease?​

Current activities are aimed at restricting further spread of the disease.

The original declaration of Control Area, established under the Animal Health Act 1995, has now been adopted in its entirety as a Control Order under the Biosecurity Regulations 2022. The risk-based permit system continues to operate and restricts the movement of oysters, and oyster equipment, into zones of similar or higher risk.

POMS does not pose a human health risk, therefore the movement of oysters prepared for human consumption is not restricted in Tasmania.

Biosecurity Tasmania contributes to ongoing disease management through:​

  • Establishing the disease risk status of various areas through a structured testing program.

  • Working with industry to maintain restrictions on the movement of oysters (other than for human consumption) and associated oyster equipment.

  • Issuing permits to allow low risk oyster movements.

  • Investigating unusual mortality events among shellfish, including  confirming the diagnosis.

  • Engaging in ongoing education and research efforts to better understand the  POMS risk factors.

  • Notifying other states and supporting negotiations for maintaining, or regaining, interstate market access.

Can Tasmanian ​​producers harvest and move stock within the state?

​Yes. The initial response to POMS in Tasmania included movement restrictions of oysters and oyster equipment while a structured testing program was undertaken to determine where the virus was present in the State. This testing program made it possible to determine where oyster movements could occur between farms with a low risk of the OsHV-1 virus. Based on the information from the POMS testing program, three zones of differing disease risk have been determined as a basis for issuing movement permits. These three zones are designated  POMS Infected, POMS Intermediate, and POMS Free. 

For movements into similar or higher risk zones:

For general stock and equipment movements (excluding movements of stock from hatcheries) Biosecurity Tasmania has issued a Group Permit to Tasmanian oyster producers which details specific conditions required for those movements to occur. The Group permit for the movement of oysters, oyster product, and oyster farming equipment into, within and from a control zone can be found here: Group P​ermit

For movements into lower risk areas:

For movements of oysters not covered by the Group Permit, including stock movements from hatcheries you must apply for a Prohibited Dealings Permit. Please email:

Further information on Group Permits, POMS zones and area classifications can be found on the POMS -Declaration of Control Area webpage here: POMS - Declaration of Control Area​ 

What can you do to​ prevent the spread of POMS to other oyster growing regions?

Familiarise yourself with the POMS risk status of the areas you are visiting, especially if you plan to engage in fishing or boating activities. If the areas are POMS infected or POMS intermediate  and you intend to move onto another estuary, you must ensure that fishing gear or other equipment are free of any oysters, sediment or biofouling:

  • Drain all water from your boat and gear; and,
  • Flush outboard engines; and, 
  • Use car/truck wash to rinse gear and equipment, boats (inside and out) and trailers. Allow car, boat and trailers to air dry.

What you can do to​​ help​

Biosecurity Tasmania encourages all community members to report any suspected aquatic disease event so that it can be investigated. 
Recreational boat cleaning is extremely effective in reducing the spread of aquatic diseases and pests. Help protect Tasmania from introduced aquatic threats by CHECK, CLEAN, DRAIN and DRY all boating, fishing and diving gear before coming to Tasmania, and after every trip in Tasmanian waters. For further information please click here: Protecting Against Aquatic Threats ​

Reporting oyste​r mortalities​​

Any unexplained and significant mortality of oysters should be reported to:


Biosecurity Tasmania - POMS Permits & Enquiries

13 St Johns Avenue,
New Town, TAS, 7008.