Professor Leo Yee Sin founded and heads Tan Tock Seng Hospital's (TTSH) Institute of Infectious Diseases and Epidemiology. She is also clinical director of the Communicable Diseases Centre.
She was awarded the Public Service Star in 2003 for her work against Sars, and is overseeing the building of the new National Centre for Infectious Diseases, which is expected to be ready by 2018.
Q: The Ministry of Health has said suspected Ebola cases will be managed at Tan Tock Seng Hospital, and Singapore had a scare last week when a woman from Nigeria was mistakenly thought to have the disease. What is the risk it will spread to Singapore?
The risk is low. We know that Ebola can spread from person to person, but we don't have direct flights from the affected African countries to Singapore. The population movement between Singapore and those countries is very small.
However, we should be prudent and monitor the situation.
Q: You've warned people not to take measles lightly. How is the risk of an infectious disease to Singapore assessed?
In general, we look at factors along the transmission chain like the transmission rate and Singaporeans' immunity as a whole. Measles has a high infection rate and one patient can infect up to 25 people in a susceptible population. But with good vaccine coverage, the risk of further transmission is low.
For the H7N9 bird-flu virus, there is no vaccine, most Singaporeans don't have antibodies against it, and we have many people travelling between China's affected coastal area and Singapore. But it does not transmit well from person to person. So the risk remains low.
The Health Ministry scans the horizon and we work very closely with them, for example by looking into protective measures and work processes.
We also have a team that looks at influenza, dengue, and all the emerging diseases. They compile a weekly, internal bulletin that TTSH staff can access. It has infectious disease data at the national, regional and international levels. The latest bulletin lists countries affected by Ebola, the number of deaths, so on and so forth.
Q: Singapore had a record 22,170 cases of dengue last year, and the number has remained high this year. What do you think is the reason?
It's partly the serotype change. Dengue has four serotypes, and when the dominant strain changes, people may not have immunity against the incoming one. The 2004 dengue outbreak was due to the same dominant serotype 1 now, and that outbreak lasted two years.
But I think more research is needed into how population changes in the past, say, 10 years, may have changed the community's immunity.
We need to know more about the ages of the people coming into our population, where they come from, are they from endemic countries and are already immune against dengue, or from areas "naive" to the disease. The results would tell us more about the community's immunity.
Q: French drug firm Sanofi Pasteur is going to market a new dengue vaccine next year. How useful will this be for Singapore?
So far, studies on the vaccine have been on people aged 16 and below. That's useful for countries where dengue spreads mainly during childhood, but in Singapore it infects mostly adults.
Minister for the Environment and Water Resources Vivian Balakrishnan also said the vaccine's effectiveness against serotypes 1 and 2 - the most common here - is just 50 and 35 per cent respectively.
Singapore recruited about 1,200 people aged two to 45 to test the vaccine's safety and the immune response, and we are now doing the final analysis after five years of follow-up. That will tell us how people of different ages respond to the vaccine.
But even if it's safe, its preventive efficacy would still need to be field-tested. Coming up with a new vaccine takes many years from conceptualisation to safety and field tests.
Q:The first virus outbreak you handled was the Nipah pig virus in 1999, where there were 11 detected cases and one death. You have said that Singapore could have been in "big trouble" then. Why?
There were several things that we didn't do well as it was the first novel virus that challenged our system after many years of "silence". We didn't give our health-care workers adequate protection. They had the N95 mask and a flimsy plastic apron that covered only the front and not the arms.
The virus couldn't spread from person to person, but if it could have, we would have been in big trouble.
The coordination between the different parties was also not effective. One party brought patients to us for assessment, another party did the surveillance and quarantine. We didn't have a pre-established relationship with them so the coordination was chaotic.
Our clinic could hold only 30 to 50 people but there were busloads of pig farm workers coming in and the whole clinic was jam-packed. They were all packed into a tiny waiting area, people with symptoms next to people who didn't have them.
We learnt a lot of things and were able to do a much smoother, better and more efficient job when Sars hit Singapore in 2003.
For Sars, we gave maximum protection to the health-care workers: N95 mask, full gown, gloves and we later added the face shield and eye goggles. It was a stark difference.
For Ebola, we will be even better. We're looking at the best we can procure. It will be like a spacesuit.
For Sars, we also immediately segregated the patients. We kept the regular clinic for routine, regular care, opened up another screening area, changed the paths so the regular cases and suspected Sars patients didn't meet. Even those in the Sars area, we immediately separated into high- and low-risk.
Q: You started a comprehensive HIV programme at the Communicable Diseases Centre (CDC) in 1995. Why?
When I started my infectious disease training in the CDC in 1989, I met a lot of HIV-positive people. They were very young, 20, 30 years old, and when I saw how they struggled with the disease, I just felt something was not right. There was no treatment available, so we could only buy time with very expensive medication, and they also had to struggle with social discrimination. Their lives were just terminated prematurely.
When I was trained in Los Angeles in 1992, half my caseload were HIV patients. They were pretty well-provided for there, with palliative care and hospice care and things like that.
When I came back to Singapore a year later, all these things were not here. I told myself, "Look, how can I abandon the patients here?", so I took up the HIV cause.
Q: You promoted hand washing hygiene long before the campaigns started. How else has being in the infectious diseases field changed your life?
When my three children were babies, the first thing I did when I got home was bathe before I touched them.
I also tell people I have "old lady" hands, because we didn't have alcohol rubs to clean our hands then. You had to use hibiscrub, which is very dry and really destroys your skin. So I have lots of wrinkles on my hands.
I also used to love to tend to my garden, but I stopped because it's just too tiring. Now when I'm home, I just relax, watch television and recover my energy.
This article was first published on August 17, 2014.
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