Floods may lead to increase in vector-borne diseases: WHO

ISLAMABAD: Floods may indirectly lead to an increase in vector-borne diseases through the expansion in the number and range of vector habitats.

According to World Health Organization (WHO), standing water caused by heavy rainfall or overflow of rivers can act as breeding sites for mosquitoes, and therefore enhance the potential for exposure of the disaster-affected population and emergency workers to infections such as dengue, malaria and West Nile fever.

It said flooding may initially flush out mosquito breeding, but it comes back when the waters recede. The lag time is usually around 6-8 weeks before the onset of a malaria epidemic, it added.

The risk of outbreaks is greatly increased by complicating factors, such as changes in human behavior due to increased exposure to mosquitoes while sleeping outside or changes in the habitat which promote mosquito breeding like landslide, deforestation, river damming, and rerouting.

Malnutrition and other concurrent infections can leave displaced populations particularly vulnerable to malaria infection as well.

In 2008, about 15% of country's population lived in areas of high malarial transmission and 4.5 million suspected malaria cases were reported, accounting for 6% of all outpatient visits and 18% of all medical admissions.

It said movement of people from areas of low endemicity to hyperendemic regions can result in high levels of transmission and infection in a population with relatively little previous exposure.

Similarly, movement in the other direction risks high levels of transmission despite having left hyperendemic areas while persons moving to areas with low endemicity but suitable vector conditions may raise the epidemic risk there.

In particular, the Anopheles mosquito vector may be prevalent in areas of stagnant water or flooding, as is seen in the country, it added.

"Although the risk of transmission of malaria can increase in the context of an emergency, effective control and the reduction of transmission is possible," Dr. Wasim Khawaja from Pakistan Institute of Medical Sciences (PIMS) said.

He added it is high time to implement preventive measures such as indoor residual spraying besides distribution of insecticide-treated nets, especially long-lasting nets.

He said people living in the affected areas should also be trained on how to use these nets which are frequently effective options in areas where their use is well-known. He added this will also have an effect on other mosquito-borne diseases.

He said malarial treatments are more complex, however, patients are generally advised to take the form of antimalarial drugs, though these must have demonstrated efficacy against local strains and rigid compliance to maintain the effectiveness of the treatment, he added.