Cautious on Mers, mad over measles

Prof Leo says an outbreak can occur with just a few cases in an unprotected population.
PHOTO: Cautious on Mers, mad over measles

SINGAPORE - Monitoring the various infectious diseases circulating around the world from her office, Professor Leo Yee Sin has much on her radar at this present moment.

The Middle East respiratory syndrome (Mers) coronavirus remains a mystery, with little clarity on how the virus is transmitted and under what circumstances.

Over in West Africa, the death toll from the deadly Ebola virus has hit 337, with doctors still scratching their head over how to stop its scourge.

Yet for Prof Leo, who heads the department of infectious diseases of Tan Tock Seng Hospital, there is also something else much less lethal but closer to home that is getting on her nerves - measles.

Although Singaporeans are given mandatory vaccine jabs as babies and in primary school, Prof Leo notes that gaps in the coverage have developed - a result of an "untrue" paper published years ago which linked the vaccine and autism.

The paper caused "a lot of concern and scares... and because of that many parents did not send their children for the vaccination", said Prof Leo.

"And, selfishly, these parents think because other parents will vaccinate their children, their own will still be protected."

While the disease has only a 0.1 per cent mortality rate even in developing countries, it is highly transmissible - a single carrier can infect one in four unprotected persons he comes in contact with.

To keep the virus at bay, there needs to be a very high vaccine coverage of at least 95 per cent.

Due to the fact that travel patterns have become more globalised, it is never safe to rule out a re-emergence of any disease, even if the number of cases has stayed low for years, said Prof Leo, pointing to the measles hot spots that have popped up of late in the Philippines, Vietnam, China, the United States and parts of Europe.

"All you need is a few cases of infection in an unprotected population and it will spread," she said.

Prof Leo added that this is the threat facing our world now in the light of emerging diseases such as Mers, Ebola and the H7N9 bird-flu virus in China, which leaves us facing challenges unseen 20 or 30 years ago.

Also as humans encroach further into the environments of animals, the chances of animal-borne viruses infecting us only increase.

Mers, Ebola and H7N9 are all examples of viruses that originate from animals, with Ebola being the deadliest of the lot with an 80 per cent mortality rate. Mers and H7N9, on the other hand, kill 30 to 40 per cent of those who are infected with the disease.

Currently, it is Mers that has been making its move around the world, having started in a densely populated area, with Ebola and H7N9 largely contained within Africa and China respectively. But, fortunately, Mers is not capable of sustained human-to-human transmission.

However there is always the question: What if it evolves? The answer is that it will - all living things do, said Prof Leo.

The reason we sometimes see a big spike in numbers, she explained, such as in the case of H1N1 in 2009, is that there was a large population that had not been exposed to the virus before and was very susceptible to it.

Now the same virus is in fact present in our environment as a seasonal infection, which does not infect someone who has had it.

"And H1N1 will go through mutations like any other virus, up to the point when it becomes brand new and unrecognisable. Then it will become a new virus strain that can infect us."

The best way to keep safe? Vaccination, said Prof Leo.

"And short of that, like in the cases of Ebola and Mers, is to understand how the virus is transmitted and disrupt that process," she added.

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