The outbreak of Covid-19 at Tan Tock Seng Hospital (TTSH) highlights a lesson we should take to heart and do something about.

The nucleus of the outbreak is Ward 9D, a C class ward with 35 to 40 patients. About two-thirds of the patients in this ward contracted Covid-19 while being treated for other conditions.

To date, the TTSH Covid-19 cluster comprises 27 patients, 10 staff and seven visitors.

A C class ward in older hospitals like TTSH is a large open room divided into sections with half-height walls, with each section housing about eight patients. This means that the air flows freely across all the sections.

All 35 to 40 patients in the ward also share common toilet and shower facilities, and depending on the section the patient is in, may be quite a long walk away.

Apart from posing difficulties for older and frailer patients, this also means that patients move frequently through the ward.

In other words, the layout makes it difficult to prevent the spread of an in-hospital outbreak - as seen at TTSH, where so many patients in that one ward have been infected with the coronavirus.

Newer hospitals built since Singapore's brush with the severe acute respiratory syndrome in 2003 have full-height walls enclosing a smaller number of patients with their own bathrooms and toilets, even in the cheaper C class ward.

The number of patients in a C class ward in the newer hospitals ranges from five to six at Sengkang General Hospital to 10 to 12 at Khoo Teck Puat Hospital and Ng Teng Fong General Hospital.

While having fewer patients in a ward does not guarantee that an infectious disease outbreak is contained within this number, it should, intuitively, be easier to contain such outbreaks than in an open ward housing as many as 40 patients.

Infectious diseases specialist Hsu Li Yang, who is an associate professor at the National University of Singapore's Saw Swee Hock School of Public Health, agreed: "Generally, the size of the cluster would be smaller if the wards have walled-off sections with their own en-suite toilets."

So the way forward seems obvious: convert the existing wards in older hospitals to smaller, self-contained ones. But while a number of older hospitals have sought to take this route, they have not been able to do so.

The continually high demand for beds meant they could not just shut down a ward that housed some 40 patients and renovate it.

Bed occupancy rates at Singapore's bigger public hospitals hover around 90 per cent, and they have to ensure that some beds, such as high dependency and intensive care ones, are always available for emergencies. This ties their hands.

Another consideration is that installing en-suite toilets in each section could mean reducing the complement of beds to make room for the new facilities.

Nevertheless, once the current pandemic is under control, Singapore must bite the bullet and renovate such older wards to improve their infection control. It will help that more public hospitals are being built, adding more beds to the national supply.

This seems not just the sensible route to take, but also an important one to prevent mass outbreaks in future.

Patients go to a hospital for care and expect a safe environment.

It would be most unfortunate if they end up contracting something like a coronavirus infection - while being treated for another serious ailment. It is worse if such an infection could have been prevented.

Professor Dale Fisher, a senior infectious diseases consultant at the National University Hospital, said older "Nightingale" wards can certainly house more patients - which makes them more efficient - but they "are quite sub-optimal for infection control".

He said: "Hospitals are a vulnerable setting and the extent of spread is proportional to the number of contacts. So yes, wards with such a layout pose a higher risk of widespread exposure."

Such risks can be mitigated by having fewer patients within a ward. Another way is to have more space between beds. Good infection control, with staff, patients and visitors all maintaining safety protocols, is a third. This is obviously not an exhaustive list.

Said Dr Asok Kurup, who chairs the Academy of Medicine's Chapter of Infectious Disease Physicians: "Maintaining optimal infection control should ideally incorporate wards with full-height walls, more single en-suite rooms, and more airborne infection isolation rooms.

"Sometimes large, open wards with decent bed separation, open windows and good ventilation may be good enough, but this is difficult to achieve."

Prof Hsu added: "It is probably too late for current hospitals, but perhaps it is time to consider whether we should keep the 'sacred cow' of C and B2 class wards in the future, with six or more persons per room, or if we should limit each room to four patients at most, which is what we see in newer European and United States hospitals."

While Prof Hsu's suggestion is a good one, it needs to be studied in the local context.

Having fewer people in a room could reduce the spread of infection, but it comes with higher costs in terms of space and staffing.

In any case, the key is to have full-height walls enclosing a smaller number of patients who will have bathroom and toilet facilities shared only by them. The actual number of patients in a ward is something the Ministry of Health (MOH) and the hospitals should decide on.

In looking at making C class wards in older hospitals safer, perhaps it is also time for public hospitals to revisit the entire concept of having two subsidised ward classes, C and B2, in the first place, particularly since the MOH has announced that the subsidy for the two classes will be merged next year.

Currently, the subsidy for C class wards is higher at 65 to 80 per cent, compared with the 50 to 65 per cent for B2 class ones.

When this change comes into effect next year, the subsidy will range from 50 per cent to 80 per cent, based on means testing, regardless of whether the patient is in a C or B2 class ward.

With that change, it would be an opportune time to decide if the two subsidised wards should be merged, given that the differences between the two in the newer hospitals have narrowed to be point of being insignificant.

B2 wards may house one fewer patient than C class wards and have separate toilets and bathrooms, as opposed to a combined bathroom and toilet (which means no one can use that toilet if someone is taking a shower).

Merging the B2 and C class wards into a single entity is a good option.

Alternatively, the ministry might want to add perks to the more expensive B2 class subsidised wards, such as air-conditioning.

Today, only the private B1 and A class wards in public hospitals have air-conditioning. Is there any reason why patients who need subsidy for their hospital stay should be deprived of that comfort?

Studies have shown that cooler air in the wards results in fewer bedbound patients having bedsores that could lead to longer hospital stays.

It is also more comfortable for the staff working in the wards.

But not all patients may want air-conditioning. Some older patients may find it too cold. Others may prefer natural ventilation, considering fresh air to be healthier.

It would be good to get public feedback on whether Singapore should retain the two subsidised ward classes, and if so, what should distinguish them.

Any changes, or even a decision not to make changes, would affect everyone, be they patients, tax-payers or just concerned citizens.