As yet another South West monsoon sweeps across Kerala, the State is left grappling with outbreaks of infectious diseases, especially dengue fever, which has become as annual a phenomenon as the monsoon itself.

Despite desperate bids by the Health department to avert a public health crisis, viral fever patients have been filling up the wards and observation rooms in almost all Government hospitals across the State. While much of the fever cases crowding the hospitals have been seasonal viral fever, often accompanied by a secondary bacterial infection affecting the chest, there is no denying the fact that dengue fever numbers are growing larger every year.

“Dengue has become so well-established in the State now that in every outbreak, at least three panchayats are involved. This is a recent phenomenon that we have had to reckon with and quite worrying because it indicates fast local transmission of the infection,” a senior public health personnel said.

Official figures cite that there have been 1,021 confirmed cases of dengue fever in the State this year (till June 27), with five confirmed deaths. But these are the cases which have been confirmed in laboratories and reported to the Health department.

Which means that clinically dengue-suspected and unconfirmed cases could be even double or treble this figure. Also, the figure quoted by the department does not reflect the dengue cases which are attended to by private hospitals as reportage from the private sector continues to be very poor.

Reports from the districts suggest that after an upsurge of viral fever cases in June, with the monsoon remaining erratic, cases have been showing a downward trend. However, with the monsoon becoming active again, it is possible that the fever cases, including dengue could go up too.

The State has been bearing the brunt of Chikungunya outbreaks consecutively for the past four years during which time almost all districts were affected. This year, though there are scattered cases from all districts, outbreaks should be expected from Wayanad and Malappuram, which have so far remained relatively unaffected, Health officials said.

This year, the huge burden of mortality related to the Influenza A (H1N1 ) infection is something else that the State had to deal with. The H1N1 virus, in its second spell since May this year, has claimed 58 lives so far and nearly 1,100 cases of the infection have been confirmed

Dengue cases are currently showing an upward trend in Thiruvananthapuram, Pathanamthitta, Idukki, Kottayam, Wayanad, Kannur and Kasargode districts . Over 600 cases are from Thiruvananthapuram, Kottayam has 300-odd cases, about 144 cases have been confirmed from Idukki. Wayanad has fewer dengue cases – about 14 – and more of Chikungunya cases this year (44 confirmed). Leptospirosis continues to be a major problem in all districts, with high mortality rate also. Thiruvananthapuram has around 180 cases, Wayanad, 25 cases and seven deaths, Idukki has also reported some 20 cases. In 2009, official figures state that the State had 1,156 cases with 126 deaths.

“The actual figures from districts will never tally with the official figure. There is gross under-reporting and often, data from the OP clinics in the periphery are collected only till 1 p.m. to avoid showing the actual number of cases, a doctor working in the periphery said.

“All plantation districts and the rubber belt have loads of dengue cases. Ernakulam is another district, where increasing urbanisation and environmental degradation has led to an explosion in dengue cases. But with most people approaching the private hospitals for treatment, the official figures do not reflect the actual situation there at all,” he added.

The high number of dengue cases in the plantation districts never reflect in the official figures because all dengue testing facilities are concentrated in urban areas, a public health expert pointed out. Thiruvananthapuram has more testing facilities, better surveillance and documentation, which naturally reflects in the high figures also.

“We are getting complacent about the annual dengue outbreak and seek comfort in the fact that our dengue mortality is still low. But this is no reflection of our better control measures; it just indicates that the doctors in the State are old hands at managing dengue now!”, he pointed out.

Dengue management/vector control strategies

Dengue and the vector primarily responsible for transmitting this disease, the Aedes species of mosquitoes, have become well-established in the State in the past decade and as soon as the rains begin, there is a surge in dengue cases also. Cases which start to trickle in by May-end with pre-monsoon showers peaks during July-August and ebbs around September-October.

Though this year, the Health department did try to plan ahead and had launched a comprehensive pre-monsoon, pre-epidemic disease-control programme -- the Four Plus Strategy—to tackle all mosquito-borne diseases and leptospirosis, the mosquitoes seem to have had the winning edge in this battle.

An explosion in the mosquito population and the manner in which the Aedes species seem to have adapted its breeding habits to the State’s climatic and geographic conditions are playing havoc with the vector management strategies adopted by the State, which has been focussing mostly on source-reduction or destruction of mosquito-breeding sites.

Vector management is a problem rid with much difficulty in the plantation districts, where control strategies are limited because more than man-made breeding sources, it is Nature which plays host to the vector.

If in the urban areas, it is the Aedes aegypti which is the primary vector which transmits dengue, in the hilly terrains, it is the tiger mosquito or the A. albopictus which is the incriminating vector. A.albopictus is a less efficient vector, but it makes up for this by its huge numbers.

Entomologists pointed out that there can be no blanket strategy for controlling the Aedes species and that strategies would have to be devised depending on the geographical terrain, climatic patterns and the nature of human and mosquito contact. In plantations, source reduction alone does not work because the mosquitoes are found breeding in tree hollows, on the wet, leafy mass on ground and even inside the tiny rubber fruit pods scattered on the ground.

Last year, at Kanjirappally in Kottayam district, A. albopictus was the primary vector responsible for the outbreak there. Though this vector is believed to breed in natural environs, in Kanjiarappally, entomologists found that this species had adapted itself to indoor breeding and that it was breeding in flower vases and refrigerator trays. Multi-pronged strategies, including intensive fogging, use of pesticides etc would have to be adopted along with source reduction in plantation areas.

Vector management is thus rid with new challenges and this is one area where in the long-term, State would have to invest heavily in research and development, it is pointed out. More entomological research – the adaptability of mosquitoes, the local climatic and geographic conditions, environmental issues -- would be crucial for the State in evolving new vector control strategies.

In the 2008 March issue of Public Library of Science journal, in the article, `Defining Challenges and Proposing Solutions for Control of the Virus Vector Aedes Aegypti’, scientists have pointed out that the universal reliance over the last 50 years on source reduction may appear logical given the vector’s domestic habitat, but obviously, it has not been working in societies at risk.

Unless there is blanket coverage of source reduction activities, conscientious execution over a sustained period and a determined leadership to monitor the execution of the programme, source reduction cannot be successful, the article said. Unless all members of the community participate in the activities, one could still be at risk from a neighbour who does not bother about source reduction.

Which is why, the article suggested, that perhaps it is time that strategies for Aedes destruction were revised, to give more attention to adult mosquitoes as in malaria prevention programmes. More focussed surveillance and improved strategies for killing mosquitoes, use of improved and less toxic pesticides for indoor residual spraying should be tried, it says.

State looking to Singapore

Geographic mapping of dengue or suspected cases of dengue are important for outbreak assessment as well as for launching control measures. Risk stratification is a strategy that the island nation of Singapore has been using successfully to tackle its huge dengue burden.

While the dengue situation in Singapore is quite different from the State’s scenario, last year, the Health department despatched its entomologists to Singapore to assess if there were lessons from the island nation’s war against mosquitoes that Kerala could adopt.

In Singapore, it is mandatory that doctors report all dengue cases to the Health Ministry, which in turn alerts the National Environment Agency. The NEA prepares a dengue spot map and any area where two cases of dengue occur within 14 days of each other in about 150 m radius is treated as a hot spot , because it indicates local transmission. Intensive source reduction and vector control measures like spraying and fogging are then launched in these hot spots.

This strategy could be adopted here too for checking outbreaks and for preventing flare-ups.

Health system’s response

Even allowing for all the limitations that dengue management might pose for the State’s health task force, public health experts are quite disappointed over the health system’s poor response to the newer challenges that the State has to face year after year.

In the public health arena, it is the doctor in the local health care institution who should play a pivotal role in leading the health care activities in a locality. But the doctors here are focussing only on the curative aspect and none has any orientation in public health, it is pointed out. Doctors mostly handle the OP clinics and the paper work and leave and there are none to supervise and monitor public health activities in the field.

“What we need is a dedicated public health cadre, with adequate training, skills and experience in public health and epidemiology at the Centre and State-level. We need personnel who are experienced in case-based and real-time disease surveillance; detection of early signals of outbreaks and immediate interventional response and coordinated control and monitoring of trends of all endemic infectious diseases which will vary from region. Most of all we need a good infectious disease surveillance system, which closely interfaced with health care in the public and private sector,” T. Jacob John, a prominent public health activist in the country and the former Head of the department of Clinical Virology, CMC Vellore, said.

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