. 2023 Feb 26;21(2):e07822. doi: 10.2903/j.efsa.2023.7822

Table 9.

Transmission pathways of SARS CoV‐2 for different scenarios in hamsters (referring to EU), probability of transmission and related preventive and control measures

Pathways	Risk factors/periods/areas	Probability of transmission (P)	Potential preventive and control measures in animals	Potential preventive and control measures in humans	Possible monitoring approach
Human > hamster In the next 12 months, what proportion of hamsters in pet shops in the EU will be infected with SARS‐CoV‐2 due to contact with infected people?	Close contact with pet Contamination of cage equipment (Port et al., 2021) No PPE or good hygiene practices when handling animals or equipment	very low to low (< 10–33%) Reasoning: Hamsters are highly susceptible to SARS‐CoV‐2 (Yen et al., 2022) Quality of evidence: low to moderate, there is only one publication describing natural infection of hamsters (Yen et al.). Hamsters however are used frequently as animal models for SARS‐CoV‐2 and high susceptibility to infection has been demonstrated by numerous publications.	Not available/ applicable	Testing PPE and good hygiene practices Avoid direct contact if infected.	Investigation in pet shop workers or breeders
Hamster > hamster In the next 12 months, out of SARS‐CoV‐2 infected hamsters in the EU, what is the proportion that will transmit the infection to at least one other hamster?	Group size per cage Density of hamsters Hygiene measures between cages	High (> 90%) Reasoning: Transmission of SARS‐CoV‐2 can take place via contact, aerosol, fomites and air (Port et al., 2021) Quality of evidence: high, there is a plethora of publications demonstrating transmission of SARS‐CoV‐2 between hamsters – by direct contact or via fomites or air/aerosol.	Reduce group size in cages. Reduce hamster density/increase distance between cages Use filter‐top cages Limit movement of animals with clinical signs and/or quarantine after movement	PPE and good hygiene practices.	Not applicable
Hamster > human In the next 12 months, out of SARS‐CoV‐2 infected hamsters in the EU, what is the proportion that will transmit the infection to one or more humans?	Close contact with pet No PPE or good hygiene practices when handling animals	Low (10–33%) Reasoning: Hamsters shed high levels of virus. Quality of evidence: low to moderate, because there is only one publication describing the transmission of SARS‐CoV‐2 from hamsters to humans (Yen et al.). Considering that hamsters shed high levels of virus, which can be detected in the air, and that virus transmits rapidly among hamsters, high amounts of infectious virus can be reached in situations where several hamsters are kept.	Use filter‐top cages	PPE and good hygiene practices. If animals tested positive wearing PPE Limit direct contact.	Monitor pet shop workers or breeders

Pathways

Risk factors/periods/areas

Probability of transmission (P)

Potential preventive and control measures in animals

Potential preventive and control measures in humans

Possible monitoring approach

Human > hamster

In the next 12 months, what proportion of hamsters in pet shops in the EU will be infected with SARS‐CoV‐2 due to contact with infected people?

Close contact with pet
Contamination of cage equipment (Port et al., 2021)
No PPE or good hygiene practices when handling animals or equipment

very low to low (< 10–33%)

Reasoning:

Hamsters are highly susceptible to SARS‐CoV‐2 (Yen et al., 2022)

Quality of evidence: low to moderate, there is only one publication describing natural infection of hamsters (Yen et al.). Hamsters however are used frequently as animal models for SARS‐CoV‐2 and high susceptibility to infection has been demonstrated by numerous publications.

Not available/ applicable

Testing
PPE and good hygiene practices
Avoid direct contact if infected.

Investigation in pet shop workers or breeders

Hamster > hamster

In the next 12 months, out of SARS‐CoV‐2 infected hamsters in the EU, what is the proportion that will transmit the infection to at least one other hamster?

Group size per cage
Density of hamsters
Hygiene measures between cages

High (> 90%)

Reasoning:

Transmission of SARS‐CoV‐2 can take place via contact, aerosol, fomites and air (Port et al., 2021)
Quality of evidence: high, there is a plethora of publications demonstrating transmission of SARS‐CoV‐2 between hamsters – by direct contact or via fomites or air/aerosol.

Reduce group size in cages.
Reduce hamster density/increase distance between cages
Use filter‐top cages
Limit movement of animals with clinical signs and/or quarantine after movement

PPE and good hygiene practices.

Not applicable

Hamster > human

In the next 12 months, out of SARS‐CoV‐2 infected hamsters in the EU, what is the proportion that will transmit the infection to one or more humans?

Close contact with pet
No PPE or good hygiene practices when handling animals

Low (10–33%)

Reasoning:

Hamsters shed high levels of virus.

Quality of evidence: low to moderate, because there is only one publication describing the transmission of SARS‐CoV‐2 from hamsters to humans (Yen et al.). Considering that hamsters shed high levels of virus, which can be detected in the air, and that virus transmits rapidly among hamsters, high amounts of infectious virus can be reached in situations where several hamsters are kept.

Use filter‐top cages

PPE and good hygiene practices.
If animals tested positive wearing PPE
Limit direct contact.

Monitor pet shop workers or breeders