Kerala is battling yet another epidemic season when dengue and leptospirosis cases soar and hospitals buckle under the sheer number of patients that fill up fever wards and crowd outpatient clinics.
The State escaped this annual phenomenon during the pandemic years 2020-22. But given the cyclical pattern in which major dengue outbreaks occur (the State had two major dengue outbreaks in 2013 and 2017), health experts expect that this year’s outbreak could overwhelm the State, not just by case numbers but by increased severity and mortality.
The first recorded cases of dengue fever and associated deaths — 14 cases and 4 deaths — in Kerala were reported from Kottayam in the year 1997. The State has been hyperendemic for all four serotypes of dengue virus (DENV) for the past two decades or more, meaning that all four serotypes are in circulation in the State throughout the year. Historically, however, the surge in cases has been due to DENV 1 and DENV 2.
In 2017, when the State had its worst dengue epidemic till date, chalking up 21,993 lab-confirmed and 66,329 probable cases with 165 confirmed and 108 probable deaths, DENV 1 and DENV 2 were the predominant serotypes. There has been a shift in this pattern since 2019 and a marked increase in the proportion of DENV 3 and DENV 4 case samples.
Whenever there is a switch in circulating dengue serotypes, a major outbreak should be expected, which is why epidemiologists fear that the State could be in for a moderately severe dengue outbreak this season.
As of July 5, the State has reported 3,933 confirmed cases and another 11,870 probable cases. Dengue mortality has shown a spike this season and already 21 confirmed and 38 suspected dengue deaths have been reported.
However, unlike dengue, the incidence pattern of which is affected by the complex interplay of epidemiological and immunological factors, leptospirosis pattern has been more or less constant in the State. Leptospirosis cases are reported throughout the year and spike after monsoon sets in. All districts are reporting cases; however, Thiruvananthapuram, Ernakulam, Thrissur, and Malappuram seem to be faring badly.
Leptospirosis has a significantly higher mortality than dengue as an accurate diagnosis even in the acute phase of the disease is difficult. Increased incidents of flooding due to climate change and changes in the interface between man-animal-environment have favoured a rise in leptospirosis, a disease which needs to be battled on the platform of One Health.
Health officials say their efforts to battle this epidemic season, when every other tropical disease presents initially as febrile fever, is complicated by the sudden surge in influenza-like illnesses, particularly the Influenza A subtype H1N1 unlike in the previous years.
H1N1 is mostly a mild respiratory disease which responds well to antivirals like oserltamivir if administered early. In vulnerable adults, H1N1 can lead to complications such as viral pneumonia and death. This season, it is the neurological complications of the disease (influenza-associated encephalitis) in young children, leading to rapid deterioration and death, often within 48 hours of the onset of fever, which has had the clinicians raise alarm.
The emphasis here is on disease prevention through the adoption of universal precautions against airborne diseases, such as wearing masks.
Dengue to wane, Lepto to surge now
Normally, the State’s dengue graph peaks around July, while that of leptospirosis in September.
“The delay in monsoon setting in the State means that the dengue peak might get shifted to July end. Going by the trend of the past two weeks, we have projected that the State might chalk up about 10,000 confirmed and about 30,000 probable cases of dengue this year,” says T.S. Anish, a public health expert and Additional Professor of Community Medicine, Manjeri Government Medical College Hospital.
But the sudden intensifying of rains now means that the dengue graph might begin to go down in another week or two, with mosquito larvae collections getting washed off in heavy rains and floods (the story might be different in urban centres such as Ernakulam and Thiruvananthapuram, where heavy indoor breeding of Aedes species in flowerpots or refrigerator trays or A/C ducts have been reported).
This means that the environmental conditions have now totally shifted in favour of leptospirosis and a significant surge in cases should be expected as many people will come into contact with floodwaters and wet marshy soil, says Dr. Anish.
Dengue is here to stay
Climate change, an increasingly urbanised environment, population movement, unenthusiastic public participation in dengue-prevention campaigns, and the inherent limitations in keeping mosquito breeding under check continue to be some of the key drivers of dengue epidemics in the State.
Extreme weather conditions in the State in recent times have favoured increased vector breeding, whereas the repeated efforts of the Health department to involve local communities in launching intensive vector control drives have only had limited success.
Public health experts point out that vector control strategies should be deployed early, before an outbreak and sustained over inter-epidemic periods to prevent escalation in transmission.
However, Director of Health Services K.J. Reena says despite launching pre-monsoon preparedness initiatives from mid-February, the State has had only limited success in reining in the dengue outbreak because public participation and involvement of local communities, which are crucial for sustaining vector control measures in a systematic manner, has been poor.
Focus on mortality reduction
There is global consensus that for tropical diseases such as dengue and leptospirosis, which are driven by complexities of weather, environment, and human host factors, the focus should be on mortality reduction and limiting the impact of the outbreaks on the population.
Over the years, the Health department has thus been focussing on drawing up standard treatment protocols for dengue, leptospirosis, and H1N1, imparting training to clinicians in the periphery and private sector, so that even when cases surge, patient care and management can keep the mortality graph down.
Health experts point out that the weakest link is often the failure to diagnose the infection early on because atypical presentations are common. Once complications set in, these patients will be rushed to tertiary care centres where crowding and shortage of critical human resources may affect the quality of care that serious patients require.
Research takes a back seat
But there are allegations that there have never been any sustained serious efforts on the part of the department towards documentation of clinical patterns in various outbreaks, proper assessment of mortality or any investment in basic research or new learnings, which can potentially improve the State’s annual outbreak response.
Dengue research is mostly confined to limited clinical studies from medical colleges. Doctors have pointed out that the profile of those afflicted by leptospirosis has changed now, as the infectious organism is often present in the soil and environment and even gardening without gloves or an infected pet animal can put humans at risk. Increasing waste accumulation in urban areas may lead to an explosion in rodent population and rains can carry rat excreta everywhere.
“The full trajectory of the transmission channels of leptospirosis from animals to the environment and then to humans has never been explored through microbiological investigations in Kerala. Despite the high mortality profile of the disease, the stock response of the authorities has always focussed solely on the blanket administration of doxycycline to the population,” a public health expert says.
“Alongside public health interventions, doctors, especially young doctors, manning the casualty, need to be trained to go beyond guidelines and use their clinical acumen to treat a patient with fever. They need to be able to differentiate between a multitude of seasonal diseases. The efforts should be to upskill clinical diagnostic capabilities, rather than playing safe with doxy administration to all,” he says.
