Acute febrile illness is the most common clinical syndrome among patients attending hospitals in developing countries, which is caused by a variety of bacterial, viral, fungal and parasitic agents. Clinical presentations of these organisms and transmission to humans, incubation period vary most of the times these findings will help in diagnosing the condition. India is an endemic to dengue and enteric fever, so there is possibility to get co-infection of dengue and enteric fever. Dengue fever is a mosquito-borne disease caused by dengue virus, prevalent in tropical and subtropical areas. Dengue virus has four confirmed serotypes, subsequent infection with a different serotypes increases the risk of complications, so called Antibody-dependent Enhancement (ADE) [1]. It can manifest as a mild infection or severe dengue including dengue haemorrhagic fever or dengue shock syndrome. Dengue virus is transmitted by Aedes mosquitoes and causing nearly 5000 deaths per year [2]. Enteric fever is a life threatening systemic bacterial disease caused by Salmonella enterica serotype Typhi, usually infect persons after 6 to 30 days after exposure [3]. Clinical manifestations range from mild to severe affecting gastrointestinal tract. It is a contagious spreads to close contacts or by taking contaminated water or food. Patients are likely to recover without complications by diagnosing early and managing with accurate antibiotics [4]. Both infections clinical manifestations are little overlapping such as fever, tiredness, body pains and headache. Both cause seasonal presentations during monsoon and they are highly fatal leading to complications like multi-organ failure and septic shock if not treated on time and dual infection can be more severe than either disease alone. For this reason and the signs and symptoms are vague and obscure, it is great demand to go for diagnostics. Various diagnostic modalities are available from a simple, rapid and less expertise investigations like immunochromatographic test, WIDAL tests to high sensitivity and confirmatory investigations like PCR, ELISA and Blood culture to diagnose these duo infections accurately and in a short period. The clinician decision making on arriving at diagnosis in these infections is compromised, also to provide insights into accuracy of diagnostics and research based data of co-infection of dengue and enteric fever is insufficient, we have tried to determine the seroprevalence of enteric fever among patients diagnosed with dengue fever at our hospital. Aim & Objectives: To determine the seroprevalence of enteric fever among dengue cases attending Government teaching general hospital, Eluru

This is a prospective observational study conducted in department of Microbiology at Government teaching general hospital, Eluru, Andhra Pradesh in association with State Reference Laboratories. Study was carried out after obtaining consent from patients. This study was undertaken for a study period of one year from July 2024 to June 2025 among all patients diagnosed with dengue positive by IgM ELISA. This study was approved by Institutional ethical committee prior to the study. Inclusion criteria: All Patients diagnosed with dengue of all ages and Patients who are willing to provide voluntary informed consent irrespective of gender. Exclusion criteria: Those patients diagnosed as enteric fever in the last 3 months and those who used broad spectrum antibiotics in the last 3 months. Sample Collection: 5ml of venous blood was collected from all the suspected cases of dengue under aseptic precautions using serum separator tube in either IP or OP patients at our hospital and the same sample is utilised for widal test. These samples were transported immediately at laboratory within 1 hour, if there is any delay in transportation sample were stored at 2-80C until 24 hours. At laboratory the serum was obtained through centrifugation at 3000rpm for 10 minutes using centrifuge in the thermostable condition. Dengue test was performed by dengue IgM ELISA and detection of enteric fever was done by performing WIDAL test. Dengue ELISA: Detection of NS1 antigen and IgM antibodies of dengue was done by ELISA test. Dengue NS1 antigen and dengue IgM antibodies capture ELISA kits were supplied by National Institute of Virology (NIV), Pune. Enteric fever- WIDAL: Salmonella Typhi bacteria detection was done by WIDAL method. WIDAL test was done by tube agglutination method in which agglutinating antibodies are against ‘O’ and ‘H’ antigens of S.Typhi and ‘H’ antigens of S.Paratyhi A and S.Paratyphi B [6]. Titers of agglutinating antibodies against ‘O’ antigens >1:160 and titers of antibodies against ‘H’antigens >1:320 were considered significant. However checking for raised antibodies titers after a week will be more reliable. Data Collection: Patient details including demographic parameters, presenting complaints, antibiotic history, family history, microbiology investigations data were collected in a Microsoft excel sheet and the data was analyzed and tabulated for a clear depiction. Statistical Analysis: A Descriptive quantitative parameters were measured as numbers and percentages.

In this study period dengue detection was done on 2696 blood samples, among them 1282 were males and remaining 1414 were females. Dengue ELISA test positive was observed in a total of 513 patients, which accounts for 19.02 % dengue in the community. These 513 specimens were further analyzed for Typhoid testing, 10 (1.94%) out of 513 were both dengue and enteric fever positive. Salmonella paratyphi A and B were not observed in this study. Fig 1. Seroprevalence of Dengue and Enteric Fever Out of 513 dengue positive patients, 288 (56.1%) were males and 225 (43.8%) were females. Both Dengue and typhoid fever positive cases were equal distribution among both sexes 50% (5 out of 10). Fig 2. Sex distribution of dengue and co-infection dengue and enteric fever Maximum number of dengue cases was noted in children and young adults, accounting 75.4% of dengue positives were noted in 0-30 years of age group. Concurrent co-infection of dengue and enteric fever was observed predominantly in the age group of 20-40 years, it was 60%. Table 1. Age wise distribution of Dengue and Enteric fever population Dengue (n=513) Dengue+Enteric Fever (n=10) Age in years No. of cases % Age in years No. of cases % 0-10 175 34.1 0-20 4 40 11-20 114 22.2 20-40 6 60 21-30 98 19.1 40-60 NIL - 31-40 42 8.1 >60 NIL - 41-50 48 9.3 51-60 14 2.7 >60 22 4.2

In India various types of mosquitoes live which are responsible for dangerous vector borne diseases like arboviral diseases, malaria. Mosquitoes breed and most active during monsoon seasons, where both urban and rural areas face challenges due to stagnant water, wet and marshy areas, poor waste management and water storage. Mass migration of population, deforestation and global climate changes are posing the risk of emergence of arboviral diseases. Dengue and typhoid fever are notifiable diseases in India. Both diseases contribute majorly to the public health problems especially during the monsoons. Due to the varied clinical presentations, these diseases are often under reported or misdiagnosed Concurrent infection with dengue and typhoid management needs a comprehensive approach including thorough clinical evaluation and diagnostic techniques. Clinical manifestations of co-infection will be more severe than individual disease, this is a warning sign for clinicians to start the treatment at the earliest. Vigna et al. published a case report on two such patients who also presented with high-grade fever, myalgia, and gastrointestinal symptoms: nausea, vomiting, and abdominal pain. Such symptoms can be seen in both typhoidand the “dengue with warning signs” group of patients [5]. In our study Dengue ELISA test positive was observed in a total of 513 patients, which accounts for 19.02 % dengue in the community. These 513 specimens were further analyzed for Widal testing, 10 (1.94%) out of 513 were both dengue and typhoid fever positive. Baba M et al [6] observed the prevalence of 4.1% co-infection of dengue and typhoid, while 92% of patients tested positive for malaria, typhoid, an arbovirus infection, or a combination of one or more of these types of infections, less than 1% of the patients tested positive for malaria alone and only 3.9% tested positive for typhoid alone. Dengue virus patients can be co-infected with various microorganisms including virus, bacteria and parasites. These co-infections with certain organisms have been observed by some studies and published [6]. Ahmed et al [7] and Sudjana et al [8] case series were reported as one case of dengue and typhoid co-infection observed in their studies. Sharma Y et al [9] showed 7.8% dengue and typhoid co- infection reported both from India and abroad. The seroprevalence of co-infection varied in different studies, it is because the season in which study conducted, patients hailing from dengue prone localities, waste management in the region, availability of resources for testing infections and water storage facilities. Dengue virus can coinfect other viruses, bacteria, and plasmodium [10]. Maximum number of dengue cases was noted in children and young adults, accounting 75.4% of dengue positives were noted in 0-30 years of age group. Concurrent co-infection of dengue and enteric fever was observed predominantly in the age group of 20-40 years, it was 60% followed by below 20 years children in the present study. Sharma Y et al [9] from North Delhi observed maximum number of dengue positive cases were seen in age group 0- 10 y. Age groups of patients co-infected with dengue and typhoid were as follows; 0-10 yrs: 5, 11-20 yrs: 3, 21-30 yrs: 2, >60 yrs: 1. Majority of the studies noted the seroprevalence of co-infection in 0-10 years; children were more prone for infections. Children expose more to infections than adults because of their playfulness in crowded areas and behavior is different. Even their immune system is not fully developed to counterattack the pathogens so they pose a risk of getting infections often [11]. Limitations of the study: This study could not evaluate the time of onset of both infection manifestations as it was difficult to follow up patients here and also we consider this point as out of scope of this study. Typhoid testing confirmation needs robust diagnostics like blood culture or stool culture and could not detect the chronic carriers due to multiple reasons. Further research works on these points may help us to find the association of dengue and typhoid. Strengths of this study: This study tried to project the seroprevalence data of dengue and typhoid and their concurrent co-infection rate. Knowing the concurrent co-infection rate by the study analysis will definitely aid in treating all cases accurately and reducing the complications and mortality rate.

Concurrent infection of dengue fever may not be so common but it can occur with other endemic diseases like typhoid fever, this will lead to more serious medical problems to the patients presenting with co-infection. Co-infection should be kept in mind when the clinical picture of either dengue or typhoid comes across during consultations. Majority is the children being affected by dengue infection and also it was noted that co-infection is common in children. To manage these cases thorough clinical history and early recognition of clinical manifestations plays a vital role which should be followed by logical diagnosis and appropriate management of severe manifestations. If not managed it with utmost importance, may lead to multi organ failure and significant morbidity and mortality.

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