You settle down in your seat in the cinema, popcorn in hand, ready to enjoy the movie. But some people around you begin to cough – and cough.

A Straits Times reader encountered this situation recently. Mr Donny Ho Boon Tiong wrote to the newspaper’s Forum page, describing how a movie outing with his daughter was marred by a couple seated next to them, who were coughing non-stop.

Many people, including the elderly, children and those who are pregnant, go to the cinema. And in such an enclosed area, where people are in close proximity, he wrote, the flu virus can spread easily.

The common cold, like influenza, is also easily spread. Both have very similar symptoms but the common cold is generally a milder disease compared to influenza.

A person with the common cold may sneeze, and have a runny nose, sore throat and mild fever.

In contrast, the flu has the potential to be more serious. It can cause severe body ache, extreme lethargy and very high fever with chills. It can also lead to major health complications such as pneumonia or even death.

That is why people who are not well should stay homeand not go to work or head to the cinema or other crowded places.

Dr Mark Ng Chung Wai, a senior consultant and chairman of the SingHealth Polyclinics Infection Control & Infectious Diseases workgroup, discusses how we can help prevent the spread of the flu virus.

We usually recover from a cold or flu. Why do we have to stay home when we are sick?

This is about social awareness. If you take the train when you are sick and don’t wear a mask, you might infect the people around you.

This is not a big problem if the flu is a mild one. But if there is an elderly person with a chronic illness beside you, things may not turn out well for him.

At work, not everyone can or wants to take sick leave when he is unwell. Should this be made a rule?

I am aware that it is not easy for some people to take sick leave.Some of them may not want to stay at home as they may have deadlines to meet or are concerned about work piling up or burdening colleagues who have to cover their duties. They may also worry that they might be judged as malingering.

Perhaps our work environment expectations need to change, so that taking sick leave when unwell is viewed as legitimate and done in the interests of our colleagues and ourselves.

This is why I emphasise the habit of thoroughly washing your hands.

Can we simply wash our hands with water?

Water alone won’t help. You can get rid of debris but not the germs, which can breed in water.

Wash your hands with soap and water. This gets rid of viruses which are picked up when your hands come into contact with contaminated surfaces. Influenza viruses from sick people can survive on surfaces such as tabletops, door knobs and light switches.

If water is not available, canwe make do with a hand sanitiser?

Sanitisers are a convenient way of disinfecting your hands, provided they are not visibly soiled. If they are, you should wash them with soap and water instead.

Is it safe to eat with our hands after using hand sanitisers?

Hand sanitisers are typically alcohol-based and they usually contain emollients, which are used to soothe and soften the skin.

The alcohol component of the hand sanitisers evaporates when it is rubbed thoroughly on the skin.

Some hand sanitisers leave a residue. It is usually non-toxic but some people may be allergic to it, while others may not be comfortable eating with sanitiser residue on their hands.

Washing your hands with soap and water is still recommended before you eat.

Why should we get a flu vaccination?

The flu vaccine is designed to protect against flu viruses circulating in the environment.

Those who are vaccinated are less likely to get sick or hospitalised due to an episode of flu. Vaccination protects you from something that can become worse.

More importantly, you are not just protecting yourself but also the people around you.

If more people are vaccinated against influenza, it becomes harder for a sick person to spread the flu, as the people around him would be protected by the vaccine.

This concept of getting members of the public to be vaccinated to the extent that the spread of influenza can be contained is called “herd immunity”.

All of us should play our part by ensuring that we get our yearly flu shots.

Why do I have to get a flu vaccination every year?

The composition of the vaccine changes in response to the change in the viruses in circulation.

Flu viruses are constantly evolving, which means that last year’s vaccine may not protect you against viruses that are circulating this year.