City warned to plan more for rise in diseases

PUBLISHED : Monday, 01 October, 2007, 12:00am
UPDATED : Monday, 01 October, 2007, 12:00am

An infectious diseases expert has urged the city to do more to prepare for a likely increase in diseases brought about by climate change.

Global warming was expected to lead to an increase in a range of infectious diseases around the world and it would be hard for Hong Kong to escape the risk, the doctor warned.

Climate change experts estimate that Earth's temperature is likely to rise between 1.8 and 4 degrees Celsius by the end of the century. This would create more warm zones, which are ideal for the growth of virus carriers, and raise the temperature of seawater, enabling the water to bear more disease-causing bacteria.

Eugene Tso Yuk-keung, head of infectious diseases at United Christian Hospital, called for residents to work harder to alleviate the greenhouse effect and to take precautions against the infectious diseases that are expected to spread more quickly and widely than before.

The World Health Organisation has warned that global warming will speed up the spread of infectious diseases such as dengue fever, malaria, cholera and some others caused by water-borne bacteria.

Dr Tso said: 'Dengue fever and malaria are usually transmitted by mosquitoes. Global warming and the increase of rainfall it causes have been creating warm and wet conditions for these vectors to thrive.'

The WHO predicted the percentage of the world's population affected by malaria would surge from 45 to 60 per cent by the end of the century due to the climate change, and a similar trend would be seen with dengue fever. Already, it said, more than 150,000 people were dying each year because of illnesses stemming from global warming.

'Hong Kong is a highly urbanised place, which means the warming process in the city is probably faster than the average of the world. This makes Hong Kong a city susceptible to infectious diseases,' Dr Tso said.

It was estimated that mosquitoes' potential to transmit dengue fever and malaria would increase 1.2 and 6.7 per cent respectively if the temperature went up by 1 degree Celsius, he added.

At the same time, the warming trend seen in seawater was another problem as it could cause water-borne bacteria to multiply.

'Anyone could fall ill after eating seafood contaminated by the bacteria or exposing their wounds to seawater.'

Dr Tso compared the seawater temperature around Waglan Island, southeast of Hong Kong Island, to the incidence of gastroenteritis, caused by a bacterium called vibrio parahaemolyticus, at the Princess Margaret Hospital between 1997 and 1999. The study results showed that the number of gastric flu cases corresponded to the rise and fall in seawater temperatures. Another disease related to climate change was influenza.

Unhealthy temperature

The epidemic potential of dengue-carrying mosquitoes increases as the temperature rises in the range of 23 to 39 degrees Celsius

Global warming and the rainfall it may bring can also increase the numbers malaria-carrying mosquitoe

Other nasties

Vibrio parahaemolyticus

A marine bacterium that may cause diarrhoea. According to Princess Margaret Hospital, between 1997 and 1999, the incidence of viruscaused enteritis rose with warmer seawater

Vibrio vulnificus

A marine bacterium that can cause septicemia and necrotizing fasciitis. Grows best in warm temperatures above 20 degrees Celsius