Not many people remember the polio outbreaks of the 1950s, but those who do won't forget how much the disease, which crippled children and ended the lives of many young adults, was feared.
Some who were around then say the terror of infection experienced in Hong Kong during the Sars outbreak was similar.
Once the polio vaccine was found, that fear evaporated. So non-threatening did polio become that we stopped thinking about why the vaccine was given. And then people began seeing the vaccine itself as a threat.
That attitude wasn't common. Other childhood vaccines, particularly the measles/mumps/rubella vaccine, were the ones seen as a threat.
But in Nigeria, the polio vaccine came under attack from religious leaders who regarded the mass polio vaccination campaigns funded or carried out by western non-government organisations as an attempt at mass sterilisation.
Enough people believed this to make child polio immunisation fail in parts of Nigeria and polio broke out in the northern part of the country. By March last year, Nigeria recorded its highest rate of wild polio virus, with 85 confirmed cases.
Isn't Hong Kong safe from what happens in Nigeria? Not any more. Indonesia is now experiencing its worst outbreak, thanks to the virus imported from Sudan - a country near Nigeria.
On March 13, a 20-month-old boy in Sukabumi district, West Java, was diagnosed as paralysed by polio. Tests of the virus found it was likely to have been brought into Indonesia from Sudan.
In the five months since that first case was diagnosed, 225 children have been paralysed by polio in Indonesia, initially in two provinces on Java island, but more recently in Sumatra and central Java.
What's important to know is that most cases of infection show few, if any, symptoms. Most people have little more than a mild cold or flu for a few days.
As the virus is most likely to infect children under five (who are prone to runny noses or mild viruses or infections), polio is hard to detect. Of those who do get sick, the most devastating form of the disease is paralysis.
When one case of paralysis occurs, infectious diseases experts estimate there are another 100 cases of undetected infection.
This means that there are thousands of cases in Indonesia right now. Because of these high numbers and the fact the disease is spreading from province to province, the World Health Organisation is now worried.
The exact words they used were 'concern is high' that it will 'spread across Asia including countries such as the Philippines, Malaysia and China'.
So are we going to see polio back in Hong Kong? I wouldn't expect to see a huge outbreak. Our public health systems are strong and most parents are very committed to having their children immunised against polio.
But not all of us have life-long immunity, and the number of people coming and going in Hong Kong makes it difficult to track and protect those at risk.
Lastly, this outbreak teaches us that we can never relax when it comes to infectious diseases.
Immunisation was and still is one of our greatest weapons against disease but is only effective if everybody at risk is immunised. The microbes that need to live in human systems are constantly on the lookout for new homes, so if a group choose not to protect themselves from a virus, it will target those people.
The anti-vaccination movement grew up in an era when we were at relative peace with the microbe world. Sadly, they've declared war on us again and we need to shield our bodies, particularly those of children.