An outbreak of Dengue Haemorrhagic Fever (DHF) in Delhi, India has authorities concerned that they may be seeing the start of an epidemic.
In total 448 cases have been reported to date in the national capital and 121 of those were last week; eleven of those have died along with two more in Uttar Pradesh where 40 cases of suspected dengue have been reported in the past month.
Health authorities have intensified efforts to contain the outbreak and 2,400 additional personnel are being deployed in fumigation and fogging activities to kill the dengue carrying mosquitoes.
Authorities are likely to declare an epidemic shortly and are urging officials to collect information on dengue patients across the state and to take prompt action to control the situation.
Dengue fever is a mosquito-borne infection which has in recent years become a major international public health concern.
The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-east Asia and the Western Pacific.
South-east Asia and the Western Pacific are most seriously affected.
Prior to 1970 only nine countries had experienced DHF epidemics, a number that had increased more than four-fold by 1995.
Dengue fever is found in tropical and sub-tropical regions around the world, predominantly in urban and semi-urban areas.
A potentially lethal complication is Dengue haemorrhagic fever, and in some Asian countries is the leading cause of hospitalisation and death among children.
There are four distinct, but closely related, viruses that cause dengue and though recovery from infection by one provides lifelong immunity against that serotype it only gives partial and transient protection against subsequent infection by the other three.
According to the World Health Organisation (WHO) there is good evidence that sequential infection increases the risk of more serious disease resulting in DHF.
The WHO says some 2,5 billion people, two fifths of the world's population, are now at risk from dengue and estimates that there may be 50 million cases of dengue infection worldwide every year.