According to sources in different hospitals and private clinics, most of these patients complained of pain in the joints and in the back of the eyeballs, dizziness, headache, general distaste for food and fever for more than five days all strong indications of dengue infection.

Half of these patients contracted dengue fever last year, sources said, adding that hundreds of cases of dengue go undetected, as patients do not get tested.

Twenty-three patients were admitted to the medicine wards at the Dhaka Medical College Hospital Wednesday while fourteen were admitted to BIRDEM hospital, seven to Banghabandhu Sheikh Mujib Medical University Hospital, four to Dhaka Shishu Hospital and one to Dhaka Community Hospital on Wednesday and Thursday.

In private clinics, at least two-thirds of the patients admitted to medicine wards on Wednesday and Thursday had symptoms of dengue fever. Of them, nine were admitted to Central Hospital, 21 to Samorita Hospital, four to Nibedita Children Hospital and thirteen to Holy Family Red Crescent Hospital.

Sources in the health directorate yesterday said accurate epidemiological assessment is being hampered as many private clinics and hospitals are not reporting their cases of dengue fever to the government control room.

Dhaka City Corporation (DCC), in the meantime, has launched an emergency drive in the city to control the growth of Aedes mosquito, carrier of dengue virus.

DCC officials early this week warned that Aedes mosquito population in the city was growing at an 'alarming rate'.

A study on the Population Density of Aedes Mosquito in city's all 90 wards revealed this week that except for a very few places, most of the city areas have 'exceptionally high density' of Aedes mosquito population capable of spreading the dengue epidemic any time.

DCC sent warning letters to several ministries recently stating that the situation was 'quite critical'.

The DCC has formed an emergency Rapid Action Force with one supervisor, one cleaning inspector, 10 cleaners and 10 spray-man in each of its ten zones covering all 90 wards. The teams have already started to act focusing mainly on destroying the breeding places of Aedes mosquito.

According to the study, DCC identified Paribagh, Museum Officers Quarter, Rokeya Hall Staff Quarter, Fuller Road, Isha Kha Road Teachers Quarter and Jagannath Hall as having the highest density of Aedes mosquito with the Breteau Index reaching 156 per cent against the normal 18 per cent.

The second worst affected area is the Old City where Breteau index ranged between 70 and 150. Shakhari Bazar, Haranath Ghosh Road, Azam Lane, Siddique Bazar, Kazi Alauddin Road, Kaishal Ghosh Lane, Wise Ghat, Goal Ghat, Becharam Deuri and Mughal Tuli areas were found to have exceptionally high density of Aedes mosquito larvae.

Kali Charan Shaha Road had the highest density with Breteau index reaching 145 in many of the houses surveyed by medical entomologists from Dhaka and Chittagong Universities.

The third most affected places with high Aedes density are Mohammadpur's Zakir Hossain Road, Mohammadia Housing, Pisciculture, Nurjahan Road, Iqbal Road and Asad Gate Avenue.

Kalabagan, Bashiruddin Road, Central Road, Elephant Road, Lalmatia, Farmgate, Monipuripara, North Dhanmandi, Mintu Road, Kakrail, Circuit House and Segunbagicha areas also have high density of Aedes population. Breteau index in these area ranged between 70 and 100.

Last year, over 5500 people were infected with dengue out of which 126 died of Dengue Haemorrhagic Fever and Dengue Shock Syndrome.

Seven teams have been commissioned in ten zones since August 8 to collect samples of Aedes mosquito larvae or eggs found in containers, which are then analysed in the DCC laboratory. Preliminary data indicates that millions of Aedes mosquito eggs are ready to hatch unless destroyed immediately.

Larvae which only grow in fresh water, were found in water accumulated inside discarded tyres, flower tubs, empty vases, small tin pots, earthen jars, discarded polythene bags, plastic containers and corners of roof where rainwater can accumulate.

Chief Executive Officer of DCC, KM Nurul Huda, termed the situation in the capital as quite frightening in the light of a possible dengue outbreak.

"It is beyond our imagination. The incidence of dengue this year could greatly exceed those of last two years as population density of Aedes mosquito is much higher this time," he said.

A World Health Organisation report last year warned that Bangladesh had some risk of dengue outbreak and must be alert to any signs of an epidemic.

In 1999, officials concerned in the health directorate ruled out the possibilities of a dengue outbreak, stating that dengue posed no threat on the population in the city.'

About a year later in July 2000, when Dengue Haemorrhagic Fever claimed a few lives, the Dhaka City Corporation Mayor Mohammad Hanif still believed that the dengue virus was being imported from neighbouring countries.

In fact, many of the people who earlier died from common viral infection were suspected to have died from Dengue Haemorrhagic Fever, which leads to both internal and external bleeding.

A large number of dengue fever cases across the country escaped detection due to lack of diagnostic facilities, experts said.

A WHO report on dengue situation since 1995 said that a high percentage of population of Dhaka and Chittagong has anti-bodies in their blood to fight dengue infection type-3, and to a lesser extent, types-1 and 2.

The WHO report also said that in 1996, Myanmmar had 83,381 cases of dengue infection with 2,243 fatalities. In the same year in India, more than 9,000 infections were reported, a fifth of which was fatal.

The growth of Aedes mosquito population is measured by the number of containers found with larvae in 100 houses. This measurement is known as the Breteau index and an index of up to 18 is considered normal.

A 1997 survey showed that the index in some places in the city had reached 30, rising further to 160 in 1999 and to an alarmingly high of 254 in June 2000. Experts said Dhaka City Corporation and the health ministry had ignored their warnings about a possible dengue outbreak.

WHO currently estimates that there are 50 million cases of dengue infection worldwide every year. Two-fifths of world's population - 2500 million people - are at risk of dengue infection.

Before 1970 only nine countries had experienced Dengue Haemmorhagic Fever (DHF) epidemic, a number which had increased by four folds by 1995.

In 1998 alone, there were more than 616,000 cases of dengue infection, mostly children under fifteen, in the Americas, of which 11,000 cases were DHF.

The latest WHO report also on 'Dengue and Dengue Haemorrhagic Fever' said, not only the number of cases are increasing as the disease is spreading to new areas but explosive outbreaks are occurring.

In Brazil about 475,000 cases of dengue was reported in 1998, more than the total number of cases combined in the continent the previous year.

An estimated 500,000 people are hospitalised each year with dengue infection with roughly five per cent of the patients dying. According to the WHO report, the most seriously dengue affected areas are Southeast and Western Pacific regions.