Introduction: The state of Kerala in the country of India has been getting on the wrong side of nature over the past few years. From raging floods to massive outbreaks of viral diseases, the state of Kerala has been in turmoil over the past few years. The rains and floods have ceased leaving behind a catastrophic world of copious vector-borne infectious diseases. Moreover, a migrant crisis has been looming over the state for the past few decades resulting in an accumulation of various other dangerous diseases from multiple different parts of the country. Even after taking into consideration the great health care facilities in Kerala there have been multiple reports of infectious disease outbreaks, especially in rural districts. This short review is written with the purpose to review the facts into a single entity that can provide solid proof and hence evoke a stricter sense of awareness among communities to minimize the losses and prevent the exigency of public health that can occur not too far away in the foreseeable future.
Methods: Various databases were searched like Scopus and Google scholar and all articles related to reported infections in the state of Kerala and the factors which can lead to the public health crisis were selected and included in the review.
Results: A multiple numbers of articles on viral infections were obtained in the various databases. Most of the bacterial infections were reported as urinary and respiratory tract infections. Migrant crisis and 2018 floods were two of the most recent contributing factors that can lead to an emergency in public health in the state.
Conclusion: There can be a sudden unexpected outbreak of infectious diseases if the government does not carefully monitor the rural districts like Alappuzha.
Kerala is a state that is present in the extreme south-western part of the nation India. Kerala is known for its high literacy rates and its vibrant culture. However, over the recent few years, it has been the hub of a myriad of natural calamities ranging from biological to meteorological. Although it has been under the temporary radar of news channels and other forms of media, the lack of long-term follow-up of the effects of these natural calamities has not been done. Over the last few years, a very minute amount of studies has been performed on the infectious disease epidemiology of the state as seen by Scopus metrics Figure 1 .
Figure 1 . The number of publications on infectious diseases in Kerala (2014â€”18).
Viral diseases in Kerala reported over the past five years
The viral diseases that have been reported over the past five years in the Scopus database include Nipah virus, Influenza, Hepatitis B, Respiratory syncytial virus, West Nile Virus, Japanese encephalitis virus, Kyanasur forest disease virus, coxsackievirus type B3, Chikungunya virus, Human Adenovirus, Measles virus, Hepatitis A virus and Dengue virus.
The disease which received the heaviest amount of global attention over the past few years has been a viral disease called the Nipah Virus disease. Nipah virus disease is caused by the zoonotic vector-borne RNA virus Nipah which belongs to the genus Henipavirus of the family Paramyxoviridae . This virus is spread by fruit bats belonging to the genus Pteropus of the family Pteropidae. Moreover, this disease is also highly infectious and can be transmitted both interspecifically and intraspecifically via both direct and indirect contact like saliva, urine, and other bodily secretions. There is no cure or vaccination available for the disease 1 .
Recently there have been many reports about the prevalence of the virus in the state of Kerala in the month of May of 2018. The mortality rate of the virus has been observed to be very high 2 .
Influenza viruses are negative-strand RNA viruses which belong to the family Orthomyxoviridae. Out of the five genera of this family Influenza A virus is transmitted via zoonotic vectors and is the reason for the multiple epidemics 3 .
Hepatitis B Virus
Hepatitis B is an enveloped partially double-stranded DNA virus or in other words, it is a double-stranded DNA virus which forms an RNA intermediate during replication. The viral infections have now been brought under control with the help of Immunomodulators and antiviral medicine 6 .
Hepatitis B was considered to be a sexually transmitted disease; however latest research on it suggests that Hepatitis B can be transferred by nail clippings and nail cutters 7 .
A survey along with a study across 59 households in a rural Ernakulam district of Kerala showed 59 people (mostly above the age of 50) were affected with Hepatitis B. All patients claim to have been bitten multiple times by insects belonging to Tabanidae family and there is a possibility of these insects acting as vectors for transmission 8 .
Respiratory Syncytial Virus
A negative single-stranded enveloped RNA virus belonging to Paromyxoviridae family is Respiratory syncytial virus. It is mainly notorious for causing bronchiolitis in Infants. There has been a trial vaccine going on the rounds by the Novavax company of USA and can be helpful to prevent Respiratory Syncytial Virus infections in infants by immunization of the mother 9 , 10 .
Direct transmission by touching, transmission by potential fomites and transmission via droplets are the suggested mode of transmission by various studies 11 .
In the study of 130 patients having acute lower respiratory tract infections, 49 were observed to be affected by the respiratory syncytial virus. After genotyping, it was found out that 32 belonged to Respiratory syncytial virus A and 17 belonged to respiratory syncytial virus B. This study showed the prevalence of both the strains of the virus in Kerala 12 .
West Nile Virus
West Nile Virus is a positive single-stranded RNA virus from the Flaviviridae family of viruses. These viruses are transmitted to humans via mosquitoes of the genus Culex 13 .
There had been many reported outbreaks of acute encephalitis reported in Alappuzha district of Kerala and upon subsequent serological tests, the prevalence of antibodies against West Nile virus was found in many of the people 14 . In 2011 there were reports of encephalitis outbreaks in Kerala attributed to the West Nile virus 15 . A follow-up study shows the long-lasting damage inflicted upon the patients who survived the outbreak 16 .
Japanese encephalitis virus
Prevalence of antibodies against Japanese encephalitis virus was found in people of the district of Alappuzha in Kerala 14 .
Kyanasur forest disease virus
Kyanasur forest disease virus is a positive single-stranded enveloped flavivirus with an icosahedral capsid. It is a zoonotic virus spread by the tick Haemaphysalis spinigera.
A lot of individuals affected with this virus have been reported in the Wayanad and Malappuram districts of Kerala. This causes severe hemorrhagic fever with various neurological disorders 19 .
Coxsackievirus type B3
Coxsackievirus type B3 is a single-stranded RNA Enterovirus. This virus is known to cause mild infections prevalently in neonates and children, however, sometimes infections by this virus can cause severe hepatitis which can lead to death 20 .
In the south-western parts of India like Kerala and Karnataka this virus has been known to cause acute flaccid paralysis and has become an upcoming problem 21 .
Chikungunya virus is a positive single-stranded RNA virus belonging to the alphavirus genus of Togaviridae family. It is transmitted zoonotically by vector mosquitoes of the genus Aedes 22 .
Molecular diagnosis of samples from various patients showed a prevalence of Chikungunya virus infections in Kerala 23 .
Measles virus is an enveloped negative single-stranded RNA virus belonging to the Paramyxoviridae family 26 .
An outbreak of measles occurred in a fisherman community of Kerala. 43 out of the 215 studied children had a history of measles. Moreover, the community was at high risk due to the lack of vaccination owing to poor awareness and living conditions 27 .
Hepatitis A is an enveloped positive single-stranded RNA virus from the Picornaviridae family of viruses. This virus is transmitted by contaminated food and water 28 .
A Hepatitis A outbreak in the Kollam district of Kerala in 2013 was attributed to occur due to the contamination of drinking water from a common source 29 .
Dengue virus is an enveloped single-stranded RNA virus from the Flaviviridae family. It is a zoonotic vector-borne disease transmitted by mosquitoes of the genus Aedes 30 .
Dengue can manifest itself clinically as Dengue hemorrhagic fever and dengue shock syndrome. Both the clinical variants have been quite prevalent in the state of Kerala. Hundred people tested positive for dengue after analysis of serum samples taken from 120 suspected dengue patients in northern Kerala. Moreover, this study showed the presence of multiple serotypes of the dengue virus 31 .
Figure 2 . A brief representation of the effects of the various factors on the population health in Kerala.
Bacterial diseases in Kerala reported over the past five years
Over the past five years, there have been very few reports of bacterial diseases as compared to viral diseases in Kerala.
Most of the reported cases of bacterial infections in the state of Kerala are as Urinary and reproductive tract infections. The prevalence of urinary tract infections was observed to be more prevalent among women than in men from the various published studies 32 , 33 , 34 . Both gram-negative and gram-positive bacteria are attributed to be responsible for the urinary tract infections. However, it was noted that there was a higher prevalence of gram-negative bacteria in the isolates taken from urinary tract infections 34 . Some of the most prevalent bacteria causing urinary tract infections in Kerala are Escherichia coli, Klebsiella spp., Citrobacter spp., Enterobacter spp ., Pseudomonas spp., Acinetobacter spp. , Staphylococcus spp. and Proteus spp. 34 , 32 .
Migration crisis and its repercussions
Migration has been a major problem for the state of Kerala for a long period. Most of the migrants are workers from the northern states who live and survive in poor conditions. The migration not only affects the socioeconomic conditions but also contributes to the accumulation of infectious tropical diseases from the northern parts of the country. Various tropical diseases like lymphatic filariasis, leishmaniasis and other vector-borne diseases like malaria are quite prevalent diseases in the northern part of the country. A study on various migrant workers showed the prevalence of infectious diseases like malaria and filariasis in the migrants 35 .
Meteorological calamity in Kerala and its implication
Heavy rainfall from the 1 st to 19 th of August in the year 2018 led to devastating floods in the state of Kerala. This heavy rainfall has led to the death of a lot of people as well as the displacement of homes of many others. As reported by the article these floods were triggered as a result of the poor reservoir management in the state. Kerala's Alappuzha district has been one of the primary places affected by the flood 36 .
The Scopus and Google scholar databases were searched using combinations of various keywords. The documents pertaining to factors posing a health risk to citizens were selected manually and were used to formulate a logical result.
We can see that most of the diseases are highly communicable in the state of Kerala. These infections are mostly transmitted by mosquitoes 1 , 2 , 14 , 16 , 19 , 23 , 35 , 37 water 29 , 32 , 33 , 34 , air 3 , 12 , 25 , 27 and direct and indirect contact 1 , 2 , 4 , 27 , 32 , 33 , 34 Figure 2 . Many of the diseases are observed to occur in the rural areas and the poorer sections of the society who usually live in poor living conditions, don't have proper access to healthcare facilities and also lack the awareness of getting rid of these diseases 8 , 27 , 29 , 33 , 35 . These communities can act as an epicenter for the spread of communicable diseases in Kerala. Moreover, migration has also led to an increase in the variety of infectious diseases 35 and can cause multiple problems in the future.
Due to the recent heavy floods, it can be hypothesized that there is a proliferation in the number of waterborne pathogens that were already present in the state of Kerala. Moreover, it can be said that due to the excessive flooding there is an increase in the stagnant water which is a breeding ground of zoonotic vectors like mosquitoes 38 . As most of the diseases were mosquito-borne and waterborne we can see the long-lasting effect that these floods may have left on the state.
Although the management of public health in Kerala has been idealistic it is important for the improvement of health care facilities in rural areas to prevent a massive outbreak of these infectious diseases 39 . The most important of all the precautions should be creating awareness of the various diseases and its infectious scenarios throughout the state especially the marginalized communities 40 . Frequent health checks in various areas for the mentioned diseases are very important. Although there has been a lot of investment in healthcare facilities in Kerala, there is still a lack of specially trained personnel 41 and hence it is very important to train people working in healthcare facilities. There should also be frequent immunization programs along with pest control of various zoonotic vectors like mosquitoes.
It can be observed from this review that more precautionary measures should be taken so as to prevent a sudden outbreak of infectious diseases in the future especially in the rural districts like Alappuzha.
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