An uneasy buzz
“That which bends up” is what the word “Chikungunya” means in Kimakonde, an African language. It’s quite an apt word considering the effect this infection has on those affected by it!
Chikungunya is a fever spread by a virus that is transmitted by the female mosquito. Female mosquitoes need proteins from mammalian blood for their eggs to develop, which is why they bite humans. Certain viruses like the dengue and chikungunya viruses collectively called arboviruses (ARthropod-BOrne viruses) make use of this requirement of the mosquitoes to ensure their own survival. These viruses were originally present only in the forest areas infecting primarily monkey species. Humans were just incidental hosts. But now due to the impact of industrialization and loss of forest cover, these viruses have made humans as their permanent hosts. The virus cannot spread from one human to another but can spread only by mosquitoes which get infected while biting an infected individual, thereafter transmitting the virus by biting an uninfected individual.
So, how do chikungunya virus spread and act on the body? Once mosquito bites, the virus spreads through the epidermal cells of the skin and reaches the inside of the body through the blood stream. The virus primarily targets muscle, joint and skin fibroblasts where the maximum damage occurs. This is the reason why patients experience intense joint pain and swelling along with rashes and acute(intense,तीक्ष्ण) fever. Apart from the tissues, a person’s immunity-mediated response is another important factor that dictates the severity of the disease. This explains why immune-compromised individuals such as very young children and elderly persons are more severely affected by this virus. This is also the reason why individuals with other underlying health complications such as like diabetes and cardiovascular diseases experience have more drastic effects due to the infection. It has to be emphasized at this point that while chikungunya results in extreme morbidity(illness,रुग्णता) and a prolonged(long,लम्बा) phase of physical disability, it is not a fatal disease.
A primary concern with respect to chikungunya treatment is the effective diagnosis. At present, there are no virus-specific detection methods and we have to resort to employing antibody-specific testing which delays diagnosis by a great extent. A study conducted by our group and our collaborators(सहयोगी; colleague) at Nair Hospital in Mumbai showed that almost 10 percent of dengue patients were co-infected with the chikungunya virus but they were not even treated for the disease. This is a big blow to patient management and disease management. While we were able to detect these co-infections because we employed reverse transcription-polymerase chain reaction (RT-PCR) to detect both the viruses, this is not practical in a hospital setting with a huge patient load and the lack of trained personnel. One may argue that dengue is more dangerous than chikungunya due to the complications of dengue as opposed to the non-fatal condition of chikungunya. But one must remember that patient management is quite different for both these infections and has several implications for disease prevention.
The vector plays an extremely important role in the spread of the chikungunya virus. When chikungunya struck in 2005, the reason it was such a huge pandemic was because the virus had mutated transform,रूपांतरित) its outside coat protein by a single amino acid that allowed it to replicate faster in another species of Aedes. This allowed the vector to transmit the virus more effectively. In the 2010 outbreak, virus strains sampled from different parts of the country were found to contain mutations on precisely(clearly,स्पस्थ्तया) three sites on their genomes. Sequencing the genome of the virus associated with the current outbreak in North India may reveal new information as to why the outbreak has been so explosive this time. Has the virus mutated again to become more virulent(poisonous,विषैला)?
Control the key
Whatever be the nature of the virus, the only effective method to control this hugely debilitating(weak,दुर्बल) infection is intense vector control and public health awareness programmes. The Mosquitoes serve as reservoirs for these viruses where the viruses survive in low amounts until they can infect a population. Having said this, we are talking of multiple issues here — the number of mosquitoes in nature at a given point in time and the amount of chikungunya virus within these mosquitoes. We recently conducted a survey where we addressed both these issues. We observed that the Aedes mosquitoes were present in small numbers even during the dry season and the viruses were present in these mosquitoes through generations. A single heavy shower was enough for the mosquito population to explode and along with it the virus populations within the mosquitoes. Every time it is a disaster waiting to happen. When the mosquito and the virus population reach a critical number, it results in outbreaks. Therefore, the only way to prevent this by is curbing(control,नियंत्रण) the mosquito population before the monsoon starts.
We face multiple issues with respect to chikungunya disease control in our country. A lack of sensitive virus-specific diagnostic tools, an absence of drugs/vaccine, poor vector control measures and public awareness contribute tremendously in escalating the problem. It is no surprise then that India is considered as the hub for chikungunya spread across the globe.