Although the monsoon rains have come late this year, the dengue outbreak in Lahore appears to have been controlled. Around this time last year, the city was gripped by fear with people largely staying indoors in the evening and each home reeking of the fumes of mosquito repellents. Dengue, which is usually not fatal unless you are bitten twice in the same season, is spread by the Aedes Aegypti mosquito, a day-biting insect that feeds on human blood.
Strangely enough, this mosquito does not breed in dirty areas — it prefers open areas where there are pools of clean water like Racecourse Park, Model Town Park and Lawrence Gardens. That is what an empirical study conducted by Khaled Sherdil, the former head of the Punjab Disaster Management Authority has discovered. “The main hotspots turned out to be green areas like Cantonment and Gulberg which have large parks and Mozang, which has the big graveyard of Miani Saab, and not the crowded interior city of Lahore,” explains Khaled. “This is also an urban phenomenon — we found out that there is no dengue outbreak in rural areas since there are lots of tadpoles which eat mosquito larvae”. Ninety per cent of the dengue cases from last year were reported from the Lahore city area.
Khaled also discovered in his study that high rainfall has a direct correlation with the escalation of the epidemic. He points out: “dengue is related to climate change because it is due to global warming that the temperature conditions for mosquitoes have become favourable”. The United Nations’ Intergovernmental Panel on Climate Change (IPCC) 4th Assessment Report that came out in 2007 states that climate change is accelerating the spread of dengue fever. According to this report, more rainfall in certain areas and warmer temperatures overall are providing optimal conditions for mosquitoes to breed and expand into new territories.
Having worked on tropical viruses earlier for his PhD that he is completing in Toronto, Khaled recently published his findings in a book entitled. Dengue: Prevention and Control, the Lahore Model of Success. The book has two graphs on temperature vs dengue incidence for 2010 and for 2011. It shows that once the temperature falls under 14 degrees Celsius, the mosquito cannot survive. The book also notes that there has been a monsoon shift by 100-200 miles over the past 10-12 years, which has moved the rainfall to the hinterland of Punjab. According to Khaled, “Monsoon plus temperature are the perfect recipe for dengue”.
So how exactly did the Punjab government control the dengue outbreak, which at one point was looking like it would become a huge epidemic with thousands infected and hospitals over run with patients? “Because of our interventions, there was a decline in dengue cases. At its peak, the epidemic had reached to 2,689 patients in various hospitals around Lahore in one week. We started spraying extensively, three sets of sprays in one day, and banned the storing of car tyres outdoors. Used tyres are like a mother’s womb for the mosquito larvae. They can remain inside the tyres for over one year and even when the larvae die, the eggs can survive,” explains Khaled.
“According to our data, during the peak week in Lahore there were 58 deaths and without our interventions, this could have gone up to 9,000 deaths in one week. We also launched a mass media campaign that proved to be very effective. People started protecting their children and the number of children admitted to hospitals with dengue fever dropped ”. There is still no vaccine for dengue — there are three different strains of the virus so it makes it harder for researchers to come up with a vaccine that will work. A person can usually survive the first incident unless they have other illnesses that can cause complications but there is one strain of the virus that can kill you if you get it a second time. There is no cure for this disease other than to rest, take analgesics for the fever, drink plenty of fluids and wait for the virus to rage through your body until it finally subsides (usually around two weeks).
The Punjab government also engaged the Ulema and the caretakers of shrines to advise people to spray their homes and protect themselves when going out. They Punjab government also contacted various private hospitals and demanded free beds for dengue cases. Khaled says that the Sri Lankan and Indonesian experts who visited Lahore to advise the government on how to tackle this virus said they had done a great job. “We were even ready with field hospitals in case the epidemic spread”.
It is now becoming increasingly clear that the upsurge in dengue, the world’s most widespread vector-borne virus, is part of a wider trend of warmer temperatures but as the Punjab government has demonstrated, advance planning and effective control can make all the difference in containing this epidemic.