5 Jan 2009
Paul Chinnock
Source: Reuters (see original article)
Source: Khamerlogue (see original article)
Source: GMA News (see original article)
Source: Bernama (see original article)
Source: Jakarta Post (see original article)
Source: Melbourne Herald (see original article)
Source: Trinidad News (see original article)
Source: BBC (see original article)
Aedes aegypti, the vector of dengue fever. The incidence of dengue fever – which is transmitted by mosquitoes and causes fever, headaches and agonising muscle and joint pains – has grown dramatically around the world in recent decades. The World Health Organization estimates that there may be 50 million dengue infections worldwide every year and that some 2.5 billion people – two fifths of the world’s population – are at risk of infection by the dengue virus.
There will therefore be considerable international interest in claims that Cambodia is making good progress in improving control of the disease. The director of the health ministry’s anti-dengue fever programme, Ngan Chantha, says that only 65 people died from dengue fever in Cambodia in 2008, down from 407 in 2007, thanks to preventive measures taken by the government and international agencies. Government figures show that 9,300 people were infected during the year compared with 40,000 in 2007, the highest in nearly a decade. Ngan Chantha credits greater funding and educational programmes for the drop in infection rates and deaths. He noted that support for the government’s control programme had been provided by WHO, World Bank, the Asian Development Bank and USAID.
The Cambodian experience contrasts with that of other countries in Southeast Asia, and also in the Americas. Philippine Health Secretary Francisco Duque recently reported there had been a rise in dengue cases – together with more cases of typhoid and cholera – for which global warming was responsible.
Malaysia also has a growing dengue problem, Health Minister Datuk Liow Tiong Lai said, ‘About 75% of dengue deaths in Malaysia can be prevented if the public take active roles in dengue prevention and control activities.’ He said 85% of infections occurred in residential premises and 80% of the breeding sites for Aedes mosquitoes were in house compounds. During 2008 the government fined nearly 32,000 people for inadequate maintenance of their compounds, nearly double the figure for the previous year.
There is concern about the dengue situation in Indonesia, where some districts are reported to be particularly badly hit. During 2008 an average of 172 people out of every 100,000 East Kalimantan residents contracted dengue fever each month, over eight times the national average of 20 cases per 100,000 people. There were 101 deaths in East Kalimantan between January and November, a death rate of 1.9% – double the national average.
It is not just developing countries that have a dengue problem. Australia has experienced an increasing incidence. North Queensland has been told to brace itself for the worst outbreak in five years; by the end of December there had already been 52 cases. Residents have been urged to take preventive measures. Apathy over prevention has been cited as a key issue.
On the other side of the world, in Trinidad, 2008 is being referred to as the Year of Dengue Fever. While the authorities have denied there is a major problem, the public perception is different and there have been allegations of a failure to spray households in areas of mosquito infestation. The British government has warned visitors to Trinidad of the risk of dengue. No figures are available although they have been promised for early this year.
WHO says that in 2007 there were more than 890 000 reported cases of dengue in the Americas, of which 26 000 cases were the life-threatening dengue haemorrhagic fever. Throughout the tropical world urbanization is increasing, creating habitats well suited to the Aedes mosquito. While global warming may well be a factor, inadequate preventive efforts in poor urban districts are of greater concern. More information is available in a WHO factsheet.
New hope
It has often been suggested that the Wolbachia bacteria might offer a way of controlling the spread of dengue. The bacteria reduce the lifespan of Aedes mosquitoes and, as only older, mosquitoes transmit the dengue virus, spreading Wolbachia among Aedes populations could in theory have a major effect. Now, Australian scientists, writing in the journal Science, report success in spreading Wolbachia in laboratory-bred mosquitoes. The researchers from the University of Queensland in Brisbane picked a strain of Wolbachia known to halve the lifespan of its host. The mosquito which carries the dengue virus is not naturally susceptible to the bacteria, so the researchers adapted it to create a successful infection. A short summary may be found in a BBC news story.
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