SINGAPORE - Six of the 10 workers linked to a chain of transmissions involving roast meat chain Hua Zai were living together and had worked in two different outlets, prompting experts to say that it is highly likely for cross-infections to occur when masks come off - at rest areas and in shared accommodation.
This comes after concerns that kitchens could be a weak link in Singapore's battle against Covid-19, although amid the pandemic, all workers involved in the preparation of food and drinks have been required to wear masks and gloves.
But these protective items may come off at rest areas or places where staff eat, making transmission of the coronavirus in these places also possible, said president of the Asia-Pacific Society of Clinical Microbiology and Infection Paul Tambyah.
Many local eateries also have very small rest areas, which could lead to crowding during breaks.
"The key is to ensure all staff are vaccinated," Prof Tambyah said.
"While waiting for this to happen, adequate spacious rest and dining space should be provided, hand hygiene equipment should be available and staff should be able to seek medical attention which might include three to five days of medical leave without fear of financial penalty."
Safe management measures at food and beverage outlets have been tightened from May 16 to June 13, with mealtimes for employees staggered. Staff also have to dine alone and put on their masks as soon as they have finished eating or drinking.
But recent outbreaks - which have seen food delivery riders testing positive for Covid-19 and fast-food chain Pizza Hut having to deep-clean three of its outlets, after four staff members at its Punggol Plaza outlet and a delivery rider at its Havelock II outlet caught the virus - have raised concerns about whether eateries are a hotbed for infections.
In Hua Zai's case, all 26 of its outlets were shuttered after seven of its staff - at the NTUC Foodfare outlet at 308 Anchorvale Road, and two other Hua Zai outlets at 476D Upper Serangoon View and Hougang Street 51 - tested positive for Covid-19 in the span of four days.
The Ministry of Health (MOH) on Wednesday (June 2) said closing the outlets was to enable deep cleaning of Hua Zai's premises and break any potential chains of transmission.
It added in a release on Wednesday night that the Anchorvale Road NTUC Foodfare cluster, where the first Hua Zai case worked, now has a 10th case but did not specify which stall she worked in. Other than the seven Hua Zai staff members, two others had worked in other stalls at the same foodcourt.
Associate Professor Alex Cook of the National University of Singapore's Saw Swee Hock School of Public Health said good hand hygiene and consistent mask wearing are important in small spaces to minimise risks, adding that operators should also try to increase ventilation into the kitchen.
Research fellow at the NUS Saw Swee Hock School of Public Health Rayner Tan said there is a higher risk of mutual infection in small spaces like food stalls, adding that owners should not deploy staff from one outlet to another.
In Hua Zai's case, a worker who tested positive had worked at both the Anchorvale and Upper Serangoon outlets.
But Prof Cook also noted that, with the Malaysian and Vietnamese staff living in such close proximity and sharing amenities like the toilet and kitchen, household transmission may be a quite likely route of infection in this case.
"We do see quite a number of household clusters, and while we can require mask wearing at work, it's not feasible to impose safeguards within households.
MOH had said on Monday that with immediate effect, all household members of persons under quarantine are to self-isolate at home and minimise their social interactions until the person under quarantine tests negative in a polymerase chain reaction (PCR) test, in part due to the high transmission rates of newer variants.
All housemates of the first patient infected in the Hua Zai household who subsequently tested positive were already in quarantine when their results came back.
Prof Cook reminded the public that the risk of them catching the virus when buying food is very low, given that dining-in is no longer allowed now.
He also added of the risk of transmission through cooked food, especially if protocol like wearing gloves is followed: "I'm sure it's possible but the question should be how probable it is. With good hygiene and mask wearing this risk should be extraordinarily low.
The Singapore Food Agency had previously said that the risk of infections of Covid-19 due to contact with contaminated surfaces of food and food packaging is "very low", and that there is no evidence for such spread.
Prof Cook cautioned against an overreaction as the number of clusters linked to food and beverage establishments remain relatively uncommon, adding: "The vast majority of us are now working from home, or have been on home-based learning. It's precisely the workers who cannot work from home who face the greatest risk of infection."
"These are the front-line workers like restaurant staff, hawkers, security guards and cleaners, among whom we have seen more cases lately."
Getting food from the eatery to your door safely
As Singapore remains on heightened alert, food delivery and takeaway purchases have increased.
While the risk of the virus being passed from food handlers to consumers is low if proper hygiene is followed, a contact-free delivery service will minimise unnecessary contact between them, as orders are placed on doorsteps and purchases paid without cash transactions.
According to prevailing MOH and Singapore Food Agency regulations, food handlers should not be in direct contact with the food at all times, and should instead wear gloves and be properly masked up.
They should wash their hands before handling food, and take time off work if they feel unwell or know of anyone they were in close contact with who had the virus.
Stall owners should ensure there are not too many workers in a single stall, so that some safe distancing can be maintained.
Again, when in the stall, they should be masked up.
Some outlets already practise contactless pickup for delivery riders, where food handlers would leave the packed food order at the pickup point without interacting with the delivery rider.
While customers and delivery staff are allowed to enter food and beverage establishments for takeaway or delivery, they must leave the premises once they have picked up their orders.
Delivery riders should also practise proper hand hygiene and be properly masked, infectious disease specialists said.