Earlier in April of this year the World Health Organization (WHO) warned that the health of hundreds of millions of people might be put at risk by the effects of climate change.

The WHO regional director, Dr Shigeru Omi, said that global warming had already impacted on lives and health and that this problem would pose an even greater threat to mankind in coming decades unless action was taken.
The WHO estimates that climate change may already be the cause of the increase in the number of deaths-- now estimated at more than 150,000 annually -- from malaria, diarrhea, malnutrition and injury from floods, with half of those deaths occurring in Asia and the Pacific.

This led the WHO to warn that the Western Pacific Region may be heading for a major dengue outbreak unless concerted effort and cooperation was undertaken quickly. The geographical reach of dengue, already entrenched in many tropical countries, has gradually expanded over the last 30 years.
The impact of climate change includes: (i) higher temperatures (some estimates suggest that the average temperature will increase by 6 degrees Celsius by the end of the century) leading to sea level rise; (ii) more frequent cyclones and droughts; and (iii) the rapid growth of various life forms (such as mosquitoes) which carry diseases.

Of greater concern is the discovery that some of the changes associated with climate change are occurring at a faster pace than had been projected. Some of the changes projected by scientists to occur in 2080 are already occurring in 2008. For example, diseases such as the West Nile virus, formally confined to the tropics, have now been found in the temperate zone such as in the northern United States and Canada.
The costs, in terms of human lives lost, are beginning to worry the WHO. In Indonesia, reported dengue cases doubled in 2007 compared to 2005.

According to experts, the higher temperatures globally contribute to the spread of dengue in several ways. First, it speeds up viral incubation in the mosquito. Second, it shortens the mosquito breeding cycle. Third, it increases mosquito feeding frequency. And all these lead to the more efficient transmission of the dengue virus from the mosquitoes to humans.

According to the WHO, dengue is transmitted by the bite of an Aedes mosquito infected with any one of the four dengue viruses. It occurs in tropical and sub-tropical areas of the world. Symptoms appear 3 to 14 days after the infective bite. Dengue fever is a febrile illness that affects infants, young children and adults.

Symptoms range from a mild fever, to incapacitating high fever, with severe headache, pain behind the eyes, muscle and joint pain, and rash. There are no specific antiviral medicines for dengue and it is important to maintain hydration. Dengue haemorrhagic fever (fever, abdominal pain, vomiting, bleeding) is a potentially lethal complication, affecting mainly children and early clinical diagnosis and careful treatment is needed to increase the survival of patients.

The recent dengue fever outbreak in Tonga has been particularly long and painful for those who suffered from it. According to various accounts, this year's episode appears to be one of the most damaging outbreaks of dengue fever. The majority of the victims who died were children.
Those who have suffered from dengue fever find recovery very difficult often feeling weak and lethargic for prolonged periods as they recover.

This, of course, is not the first time that Tonga has been affected by a dengue fever outbreak. It is notable, however, that the New Zealand Ministry of Foreign Affairs and Trade has issued a travel advisory on the dangers of dengue fever for New Zealanders travelling to Tonga (as well as New Caledonia and Palau).

However this particular episode may be a warning sign of the growing danger of a potential epidemic that has the capacity to cause great hardship in our community and to affect economic growth and jobs.

The outcome of more episodes of dengue fever is likely to be lower economic production, as affected workers are forced to take time off work, and in the case of some families, the loss of loved ones. A general epidemic of dengue fever can lead to lower food production, lower economic activity, and lower tourism earnings especially if tourists are turned away by the fear of catching dengue fever.

What then can we do to minise the impact of future dengue outbreaks?

The health authority has been working continuously with the public to reduce the spread of mosquito breeding areas. But this may not be enough. Perhaps an integrated approach which takes in other sectors such as roading, sanitation, drainage, tourism development as well as greater public awareness holds the key to reducing the potential threat from dengue fever and other related diseases.

It is important that an assessment be undertaken as to whether Tonga is up to the task of managing this new challenge. We need a more proactive approach to minimize the risk of diseases spurred on by climate change contributing to lower economic growth and job creation.