Image: Child undergoing scan at Dengue High Dependency Unit Negombo General Hospital 

This interview was originally published by the Dengue Vaccine Initiative (DVI).

Dr. Tissera received his bachelor’s degree in medicine and surgery in 1995 and his residency training in the Provincial General Hospital in the remote mountainous region of Badulla. After being posted in Ampara, the District capital city of the then war-torn eastern province in Sri Lanka, he learned about the basics of public health, in a new light -- hands on, under ongoing civil unrest and hostilities.  Dr. Tissera joined the Central Epidemiology Unit subsequently, and in 2005 was conferred a board certified consultant in public health. From 2006-08, he worked in London as a post doc both at the Health Protection Agency Centre for Infections and the Department of Health.

Dr. Tissera received funding from DVI’s precursor, Pediatric Dengue Vaccine Initiative (PDVI) to establish an enhanced fever surveillance to generate estimates of the burden associated with clinical dengue and dengue infection in the pediatric population. This project helped to obtain reliable, real-time information on epidemiology and virology of dengue in an endemic urban community in Colombo, Sri Lanka. For this and his other contributions to the field of dengue, DVI highlighted him as its Spring 2015 Dengue Champion, a recognition given to a leader in dengue research and control via DVI's quarterly newsletter.

How would you describe the burden of dengue in Sri Lanka?

Dengue is a complex disease. It comes in waves and it continues, to this day, to be a major problem, particularly in urban areas in Sri Lanka. It affects, by and large, a greater number of children and adolescents. On top of that, it has now expanded to affect young adults and adults too. Dengue has now evolved from a public health problem to a social problem in terms of the burden. It’s a problem for everyone, including the advocator, the policy maker, health personnel, local authorities and the community at large. Being a social problem, there is no single solution; we need multiple approaches.

Multiple dengue viruses are transmitted throughout the year in this country. Although the virus was first found in early 1960s, it was not until the beginning of 1990s that dengue hemorrhagic fever (DHF) the more severe form became endemic. Since 2000, the magnitude of dengue epidemics have increased and the viruses started to spread from urban to semi-urban and rural settings. Cases were reported from all districts in the island.  From 2009 – 2013, Sri Lanka experienced an exponential increase in dengue cases, with an average of 35,000 cases per year and an incidence of 175/100,000 population reported nationally.

Today, however, Sri Lanka has reached the lowest-ever case fatality rate of 0.2% (47,258 cases with 97 deaths) in 2014 from a high 5% and 1% in 1996 and 2009 respectively, despite the increase in the proportion of DHF to 10-15%. Standardized early detection and management of cases based on national guidelines have significantly contributed in lowering the mortality over the past several years.

How did you get involved with dengue?

For the last 15 years, I’ve been involved particularly with dengue. Dengue “came on my shoulder” to further strengthen disease surveillance; work on clinical management guidelines; and on developing national strategic plan on control and prevention. In 2009, we developed and adopted our own guidelines on clinical management and today, these are being used outside Sri Lanka as well. This was definitely a turning point for dengue in Sri Lanka.

Since 2013, I’ve been heading the National Dengue Control Program. At the national level we have two key organizations: the Central Epidemiology Unit, which includes the disease surveillance for communicable diseases comprising the vaccine-preventable disease center where I’ve been a medical epidemiologist working on dengue. I also head the National Dengue Control Program, on efforts for controlling mosquito vectors at a nation-wide scale here in Sri Lanka. For this work, my team and I have focused on 4 approaches: (1) social action; (2) environmental management (for vector control); (3) health education; and (4) law enforcement.  

What measures are being taken to control dengue in Sri Lanka?

Sri Lanka is advancing responsibly to reach a case-fatality rate below 0.1% through capacity building by early detection and management of DHF.  Over the past several years a number of activities were initiated to strengthen the clinical management and the prevention of dengue. Establishing high-dependency units with necessary equipment including portable ultrasound scanners in all major hospitals - to detect plasma leak early, training of clinical staff based on national guidelines, institutionalizing mandatory patient monitoring charts, and regular clinical and death audits were the key activities on clinical management.

Additionally, continued dedicated vector control activities using adulticides and larvicides alone is showing little effect in preventing seasonal outbreaks. However, integrated vector management led by source reduction campaigns with the participation of diverse groups of stakeholders, based on strong real-time web based epidemiological and entomological surveillance data on an environmental management platform is gradually gaining momentum as evidenced by steady decline in positive breeding places prior to dengue season and community response.

A unique opportunity was created with the end of the 30 year armed ethnic conflict in 2009 which released a vital source of trained and disciplined human capital who could be mobilized to augment systematic premises inspection campaign. Fundamental relationship between built environment and health is just beginning to re-emerge from Sri Lanka. With rapid urbanization, probably being one of the main drivers of dengue resulting in public-health and built environment professionals working closely together than ever before to address the needs of the communities they serve. 

In 2011, Lahore, capital of Punjab Province, Pakistan experienced its first major dengue epidemic, one of the largest to be reported in the region, and on the request made by the government, a multidisciplinary national team from Sri Lanka with both clinical and preventive expertise was sent over to assist. Early identification and management of DHF, strengthening laboratory capacity to perform mandatory complete blood counts (CBC) on all febrile patients by day 3 of illness, introduction of bedside microhaematocrit machines to guide fluid therapy in DHF, establishing high dependency units and training a master trainer group of clinicians was initiated by the Sri Lankans. These efforts led to the continued good clinical management practices saving many lives. 

What has been a major challenge in understanding dengue disease in Sri Lanka?

Ability to predict and explain the epidemiological and clinical presentations of dengue using currently available knowledge is as yet rather limited. To understand the power of transmission of dengue infection and disease both temporally and spatially in endemic settings the then PDVI facilitated a number of projects globally. The community cohort among children living in Colombo Metropolis

established in 2008 is now expanded and being followed up to date, currently supported by the European Commission funded Dengue Tools (www.denguetools.net) project. There is emerging evidence to suggest that actual increase in cases is due to introduction of new strains of viruses as well as expansion of the range of the virus. As such, the change in epidemiology of dengue in Sri Lanka reflects events in other parts of the subcontinent also documenting substantial increases in cases as well as detection of new virus strains.

How is Sri Lanka involved with the dengue vaccine development?

Sri Lanka is the location for the upcoming Phase III Takeda dengue vaccine clinical trial. We were chosen together with four other Asian countries. Well established endemic disease burden, with co-circulation of multiple serotypes, availability of epidemiological, laboratory and clinical infrastructure facilities and expertise together with a very supportive community were the key factors for selection.

Undoubtedly, one of the long term solutions to dengue is going to be a safe and effective vaccine.  It is imperative that dengue vaccine trials be conducted in countries like Sri Lanka, given the heavy burden of disease and the distinctive strains of dengue viruses circulating in the region. Findings of research studies conducted in the region will no doubt be vital for designing future vaccine trials in South Asia and for making policy decisions about how best to introduce vaccines when they are made available for wider usage. 

What more could be done in terms of advocacy and communication for dengue vaccines?

In global perspective dengue is still considered a Neglected Tropical Disease. However, given its very high disease burden especially in south and south-east Asian regions with substantial morbidity and mortality no doubt it deserves more attention. It may be the perception that dengue affects only certain tropical and sub-tropical regions with mostly less affluent and marginalized populations. This is not true. So, we have a problem knowing the real burden of infection and the disease. We all need to do more to understand this, and it’s crucial that we continue to embark on more fundamental and operational research work.   

The challenge lies in when you want to introduce the vaccine. How will you select the target groups, which area is the most vulnerable and how to do catchups? These decisions will have to be based on scientific evidence.     

I honestly think at some point in the near future, that governments have to confront the slow pace in the development of one or multiple dengue vaccines, to stem the tide. In the meantime, organizations such as DVI will have a crucial catalytic role in bringing the industry and the countries together in a common platform.  The raging epidemics are definitely an early warning for all of us to make more efforts to intensify our attention on dengue.