To beat dengue, know thy enemy

This story was first published in The Straits Times on Nov 18, 2013

IN 2005, Singapore reported 14,000 dengue cases, the highest number in its history.

This year, however, has been worse. By October, the number of reported cases had passed 18,000, with six deaths.

Not surprisingly, a common question is being asked: "Are we making good progress in the management of dengue?"

Despite the fact that dengue has existed in Singapore for decades, the disease still holds many mysteries. Prevention is important, of course, but that is not the only problem.

As an infectious disease specialist who has witnessed several large dengue outbreaks, I am challenged all the time to understand the disease better so as to develop more effective ways to diagnose and treat dengue patients.

Fortunately, progress is being made, but much more research is also needed.

Singapore's experience has shed more light on two issues. The first is the vulnerability of older adults, while the second has to do with hospitalisation rates.

Older patients more vulnerable

ALL four sero-types or variations of dengue are in circulation in Singapore and in most parts of the world. However, while most places experience dengue as a childhood disease, in Singapore most victims are adults, and in recent years, older adults.

Research carried out by Stop Dengue in Singapore shows that older adults stricken by dengue tend to have fewer and less common symptoms. This makes diagnosis very challenging.

Older individuals also have a higher risk of complications. This is evident in Singapore's statistics. Fatalities are disproportionately higher in older individuals, particularly those with pre-existing medical ailments.

More research is needed to further understand how the immune system responds to dengue and how this might vary with the age of the patient.

Fluid replacement is a common approach to plasma and fluid leaks in the young. However, it does not work very well in the treatment of older adults, who are likely to have hypertension, diabetes and chronic heart disease that make their care more complex.

If struck by dengue, older people are more likely to bleed internally and suffer damage to other vital organs such as the kidney, the liver, and the brain.

In addition, any alteration of their immune system due to ageing might predispose them to a higher risk of an accompanying bacterial infection that can trigger a string of side effects leading to unfortunate outcomes.

In recent years, more countries are reporting a seeming shift of dengue towards adults and senior citizens. In fact, there is keen international interest in Singapore's research and management of the disease.

Hospitalisation not always best option

IN 2005, about 70 to 80 per cent of 14,000 dengue patients were hospitalised.

Of the 14,000 cases notified to the Ministry of Health in 2005, about 70 to 80 per cent were hospitalised. Doctors are required to report the cases back to MOH.

This meant that at the height of the epidemic, approximately 10 per cent of hospital beds were occupied by dengue sufferers. The situation crippled the health-care delivery system. Emergency departments were overcrowded, and non-urgent surgeries had to be deferred. Other patients with chronic conditions were not given full attention either.

During this year's outbreak, the proportion of dengue patients who have been hospitalised has declined by more than half to approximately 30 per cent.

Beds occupied by dengue cases in public hospitals are now barely exceeding 1 per cent of the total available, compared to 10 per cent in 2005.

This helps to ensure that hospitals can continue to admit other non-dengue patients who require hospitalisation.

The lower hospitalisation rate can be attributed to several factors.

First, research findings identifying the risks associated with the progression of the disease have helped to focus attention on those who need inpatient care. Doctors are now better able to identify and properly care for dengue patients who need hospital care.

Second, sharing of knowledge and experience across all health-care levels has given doctors the confidence to treat patients in clinics. Doctors in Singapore are now better able to manage the care of dengue patients in the community.

Last but not least, the community is more aware of the fact that not all dengue patients require hospitalisation. Dengue patients need lots of rest to enable the body to fight against the infection. Under the care of their family physicians, a patient's home provides the most comfort for rest and recovery.

Some might ask if the lower bed occupancy rate by dengue patients implies a compromised level of care. The statistics, however, suggest otherwise. In the 2005 outbreak there were 27 fatal cases. So far there have been six fatal cases this year. And this is despite the larger number of cases and the lower hospitalisation rate.

Research has and will continue to play a significant role in helping us understand and treat the disease. As Sun Tzu says, "Know thy self. Know thy enemy. A thousand battles, a thousand victories."

The writer is director of the Institute of Infectious Diseases and Epidemiology at Tan Tock Seng Hospital.

This story was first published in The Straits Times on Nov 18, 2013

To subscribe to The Straits Times, please go to