Dengue is an important vector-borne disease, acquired through the bite of female Aedes albopictus and Aedes aegypti mosquitoes, which need to feed on human blood to lay their eggs; the latter being the primary vector worldwide and in our country.1 The dengue virus (DENV) is an RNA virus, belonging to the Flaviviridae family and the Flavivirus genus. It is considered one of the most important and prevalent arboviruses, with four identified serotypes (DENV 1-4). ² The World Health Organization has classified dengue fever according to its clinical presentation, allowing for stratification and targeted care, focusing on the signs and symptoms that indicate warning signs, thus facilitating timely hospitalization for close monitoring. The current classification remains that defined in 2009, which divides dengue into Dengue without warning signs, Dengue with warning signs, and Severe Dengue. The course of the disease has three clinical stages: febrile, critical, and recovery. In the febrile phase, the patient presents with fever lasting 2-7 days, associated with general malaise, headache, retro-orbital pain, rash, anorexia, nausea, vomiting, and generalized myalgia and arthralgia. Neutropenia, leukopenia, and lymphocytosis are common in the complete blood count; in the critical phase, the fever subsides, and leukopenia and thrombocytopenia worsen, along with increased capillary permeability, leading to plasma leakage and a proportional increase in hematocrit. Uncorrected shock, along with thrombocytopenia, can lead to disseminated intravascular coagulation and massive hemorrhage, increasing mortality. ³

To conduct epidemiological surveillance of dengue infection in Mexico, the General Directorate of Epidemiology has adopted a classification system for dengue disease, categorizing it as Non-Severe Dengue, Dengue with Warning Signs, and Severe Dengue. The latter two categories require priority referral to hospital care. ⁴

For the confirmatory diagnosis of dengue, specific laboratory tests are available. The first is nucleic acid amplification using quantitative reverse transcriptase polymerase chain reaction (RT-qPCR). This test is performed within the first 5 days after symptom onset using a blood serum sample. During this same period, the NS1 non-structural protein antigen can also be detected. After the fifth day of symptom onset, following the host's immune response, antibody production begins, with IgM immunoglobulin being used in this stage for the confirmatory diagnosis of dengue. ^3,4,5

Among the epidemiological factors identified in countries where dengue is a public health problem is that the most affected age group is adolescents and young adults, people who perform outdoor work or occupational activities, and those who live in areas without public drainage systems or regular garbage collection. ⁷

The presence of the disease in almost all continents worldwide is linked to the expansion, proliferation, and spread of the vector, population growth, and unplanned urbanization. The countries most vulnerable to dengue outbreaks or re-emergences are those that lack efficient implementation of programs to control vector proliferation, do not guarantee a continuous water supply, lack community involvement in waste management, and have weak political commitment.¹ Dengue fever is a disease present worldwide; Southeast Asia and the Western Pacific are hyperendemic areas, according to Verma (2023). His study indicates that approximately 75% of all dengue cases worldwide originate in these regions. India is considered the epicenter of dengue, contributing approximately 34% of all cases.⁹

Regarding the Americas, according to the latest epidemiological situation bulletin on arboviral diseases, by epidemiological week 40 of 2022, 2,781,316 cases of arboviral diseases had been reported, of which 89.9% were dengue cases. According to data from the Pan American Health Organization, there was intense transmission of the dengue virus during 2022, likely due to the fact that, following the COVID-19 pandemic and related social activity restrictions in the previous year, there was a 165% increase in dengue virus transmission. In Mexico, up to epidemiological week 40, 36,926 cases were reported, representing 1.5% of all cases in the Americas. ¹³

The presence of dengue infections and outbreaks is not new; it has been circulating in our country since the 1970s. Since then, the DENV-2 serotype was identified, followed by DENV-4 and DENV-2 in the 1990s, as shown in the study by Hernández et al. (2020), which investigated the implications of dengue serotype diversity in Mexico. ¹¹

In Mexico, dengue is the most common arboviral disease. Prior to the COVID-19 pandemic, in 2019, Mexico experienced a dengue outbreak, with more than 41,000 cases, a 226% increase compared to previous years. There was a decrease in cases in subsequent years, likely due to the COVID-19 pandemic in 2020, as mentioned in the study by Fonseca et al. (2020), which examined risk factors for hospitalization and mortality due to dengue in the Mexican population. ¹²

Currently, dengue fever has become an important public health problem, persisting and increasing in several countries worldwide. Among the factors that have perpetuated its presence are demographic, social, and biological aspects. The objective of this study is to understand the clinical picture and epidemiological factors of patients hospitalized with a diagnosis of dengue fever during the dengue outbreak at General Regional Hospital No. 1 in Ciudad Obregón.

An observational, descriptive study was conducted using hospital records for confirmed dengue cases generated by the epidemiological surveillance unit of the General Regional Hospital No. 1 in Ciudad Obregón, Sonora, obtained from the SINAVE platform, during the period from September 2022 to February 2023. Inclusion criteria were patient records of any age and gender, included in the SINAVE platform and reported by the unit with a confirmed diagnosis of dengue, during the dengue outbreak in the municipality of Cajeme, from September 1, 2022, to February 28, 2023. Records in the SINAVE platform were incomplete, those related to outpatient care, or those lacking confirmatory test results from laboratories accredited by InDRE were excluded. Data on clinical and epidemiological factors of dengue were collected, including age, sex, municipality of residence, town/village of residence, neighborhood, occupation, hospitalization, initial diagnosis, comorbidities, pregnancy, number of days from symptom onset to presentation, warning signs, fever, headache, myalgia, arthralgia, retro-orbital pain, nausea, vomiting, rash/petechiae, fluid accumulation, severe abdominal pain, mucosal bleeding, gingival bleeding, epistaxis, decreased platelet count, elevated liver enzymes, signs of shock, date of laboratory sample collection, RT-PCR Triplex, ELISA IgM, discharge to home or transfer, and discharge due to death. Qualitative variables were summarized using absolute and relative frequencies and percentages; quantitative variables were summarized using measures of central tendency (mean, median, mode) and measures of dispersion (range, standard deviation, and variance). The data were entered into SPSS version 2.0. Bivariate analysis was performed using the Chi-square test for categorical variables and the student’s t-test or Mann-Whitney U test for parametric variables. Additionally, a bivariate analysis was performed according to the type of variable. The odds ratio, or prevalence ratio, was used as a measure of risk, with a 95% confidence interval considered valid, and a p-value of < 0.05 was considered statistically significant. This research study complied with the ethical guidelines and general principles established in the Regulations of the General Health Law regarding health research (published in the Official Gazette of the Federation on February 7, 1984) and was approved by the local health research ethics committee; furthermore, it posed no risk to the participants.

From the data obtained, 12 cases were identified as severe dengue and 206 as dengue with warning signs, with a ratio of 1:17. Of the total cases, 6 deaths were recorded, all of which were classified as severe dengue. The epidemiological characteristics of the cases included demographic aspects, such as gender: 85 (38.9%) were male and 133 (61%) were female. (Table 1) The average age of the cases was 33.73 years, with a minimum of 2 years and a maximum of 89 years, and a standard deviation of ±19.35 years. (Table 2) Regarding the location of the patients, the distribution between urban and suburban areas was analyzed. The results showed that 135 patients came from urban areas, specifically Ciudad Obregón (114, 85%), Navojoa (12, 9%), Huatabampo (8, 6%), and Mexicali (1, 0.7%). The remaining 84 patients came from suburban areas, mainly San Ignacio Rio Muerto (8, 9.5%), Villa Juárez (8, 9.5%), and Etchojoa (4, 4.8%). (Table 1.1) The distribution of patients by municipality of residence showed that 128 (58.7%) resided in Cajeme, 31 (31%) in Navojoa, 13 (6%) in Etchojoa, 13 (6%) in Huatabampo, 11 (5%) in Benito Juárez, 8 (3.7%) in San Ignacio Rio Muerto, 6 (2.8%) in Bacum, 4 (1.8%) in Rosario Tesopaco, 2 (0.9%) in Guaymas, 1 (0.5%) in Álamos, and 1 (0.5%) in Mexicali. According to the occupational distribution of the patients, 62 (28.4%) were students, 60 (27.5%) were homemakers, 54 (24.8%) were employed, 12 (5.5%) were retired/pensioners, 6 (2.8%) were engaged in agricultural, forestry, hunting, and fishing activities, and 5 (2.3%) had other occupations. (Table 1). Regarding the clinical presentation of the studied cases, 218 (100%) had fever, 214 (98%) had headache, 208 (95%) had myalgia, 199 (91%) had arthralgia, 139 (64%) had retro-orbital pain, 136 (62%) had nausea, 109 (50%) had vomiting, 26 (12%) had rash, 39 (18%) had petechiae, 2 (1%) had fluid accumulation, 51 (23%) had severe abdominal pain, 24 (11%) had mucosal bleeding, 44 (20%) had gingival bleeding, 38 (17%) had epistaxis, 192 (88%) had decreased platelet count, 3 (1.4%) had elevated AST or ALT levels, and 12 (5%) had signs of shock. (Table 2). Among the patients' comorbidities, 16 (7.3%) had systemic arterial hypertension, 12 (5.5%) had type II diabetes mellitus, 2 (0.9%) had chronic kidney disease, 14 (6.4%) had other diseases, no patient had immunosuppression, and 174 (79.8%) had no comorbidities.

Among other significant conditions in the patients, one patient had bone marrow aplasia, one had rheumatoid arthritis, one had asthma, one had epilepsy, one had fibromyalgia, one had hypothyroidism, one had lupus and antiphospholipid syndrome, one had severe preeclampsia at 30 weeks of gestation (resulting in maternal death), and two were in the postpartum period. During the study, 32 (14.7%) pregnant women were identified. Regarding discharge status, 212 (97.2%) were discharged in stable condition to their homes or transferred to another medical facility, while 6 (2.8%) died. In the analysis of cases according to the confirmatory test for classification, 162 (74.3%) underwent real-time PCR, 54 (24.8%) had IgM antibody testing, and 2 (0.9%) had NS1 antigen detection. The serotype identified in 100% of the cases was Serotype 2. The time elapsed from the onset of dengue symptoms (based on the operational definition of a suspected dengue case) to the onset of warning signs that led to hospitalization was studied, finding a mean of 3.9 days, a median of 4 days, a standard deviation of 1.8, a minimum of 0 days, and a maximum of 10 days (Table 3). A bivariate analysis was performed to examine the risk relationship between pregnancy and the dengue diagnosis, finding a risk of 1.892 for severe dengue, 95% CI (0.253–14.159) with a p-value of 0.523. The fatality rate for dengue fever was calculated according to its classification, and it was found that there were no deaths among patients with dengue fever with warning signs, while there were 6 deaths among patients with severe dengue, resulting in a fatality rate of 2.8%.

This study found that the main epidemiological factors of patients hospitalized during the dengue outbreak at Regional General Hospital No. 1 were a predominance of females (61%), an average age of 33.73 years, with students being the most common occupation (28.4%), followed by domestic workers (27.5%) and other employees (24.8%). Most patients were from urban areas (61.9%). There were 6 deaths from severe dengue, resulting in a fatality rate of 2.8%.

The behavior of dengue disease has been changing over the past 60 years, as human populations have evolved, and so have infectious diseases, since dengue is closely linked to social and demographic changes, such as disproportionate population growth, increased population movement, urbanization, and inadequate public health infrastructure to control the spread of the vector, as argued by Varsha et al (2021). ¹⁹

According to Durand et al (2022), in their study measuring the frequency of severe dengue cases during an epidemic in Peru, they found that the average age was 23.8 years, males were predominant, and there were no deaths during the study. 20 Meanwhile, in India, Abhijit et al. found in their study that dengue cases were more prevalent in suburban areas due to patients' exposure to agricultural activities, as well as a higher incidence among males than females. ⁶

Sahidur et al. (2021) identified no significant differences between age, gender, or location of the cases. Carhuamaca et al (2021), in their dengue prevention study, found no association between age, sex, marital status, or employment status and dengue prevention. ⁸

Fonseca et al (2021) found that among the comorbidities with the highest risk of hospitalization were cirrhosis (OR: 8.8), renal failure (OR: 6.6), immunosuppression (OR: 5.6), diabetes (OR: 4.6), and hypertension (OR: 3.1), while those associated with a higher risk of mortality were renal failure (OR: 11.4), diabetes (OR: 3.1), and hypertension (OR: 2.4). Pregnancy was associated with both, with an OR of 7.6 for hospitalization and an OR of 6 for mortality. In this study, 79.8% of the population had no comorbidities; the most frequent comorbidity was hypertension (7.3%), which is reflected in the 1:17 ratio of severe dengue cases to dengue with warning signs. ¹²

Villamil et al (2022) described that dengue resolves within a week, with complications such as shock or bleeding occurring between days 3 and 5 after the onset of fever. 21 On the other hand, in India, it was found that patients with confirmed dengue presented to the hospital on average 4 days after the onset of symptoms (Prasad 2022). 6 This study analyzed the time elapsed from the onset of symptoms to the appearance of warning signs, with an average of 3.96 days, coinciding with the time when patients seek hospital care.

Regarding the clinical picture of dengue, Echeverria et al (2022) found that the most frequent warning sign was pleural effusion, and for severe dengue, it was shock, with a mortality rate of 2%. No associated factors were found. They confirmed that vital signs were early indicators for detecting severe forms of dengue, and that 75% of all patients had a decrease in platelets. ²²

In this study, a decrease in platelets was also predominant, occurring in 88% of patients, followed by severe abdominal pain and gingival bleeding, which were the most frequent warning signs. As Prasad et al. (2022) mention, all patients showed thrombocytopenia, which they consider an important laboratory parameter for establishing a clinical diagnosis of dengue. ⁶

In a cohort study conducted in Brazil, the association between severe dengue and pregnancy-related maternal deaths was analyzed from 2007 to 2012. The study found that dengue during pregnancy tripled the risk of maternal death (0.1% 95% CI [1.3-5.8]), and that severe dengue increased the risk of maternal death 450 times (95% CI [186.9-1088.4]). Preeclampsia was the cause of death in 25% of the patients with dengue. The mechanism by which severe dengue is associated with increased maternal mortality is not yet fully understood. However, a possible etiology is the inflammatory process that could affect placental tissue and cause further hemodynamic alterations, in addition to those already present during pregnancy, according to Mulik et al (2021). 19 In this study, one case of maternal death was identified in a woman with a diagnosis of severe dengue at 30 weeks of gestation. She did not develop preeclampsia, but had a pre-existing comorbidity of chronic nephropathy. The analysis showed a risk ratio of 1.89 (95% CI [0.253-14.159], p=0.523) for pregnancy and severe dengue, compared to women with dengue with warning signs, although this was not statistically significant. Durand et al (2022), when comparing the behavior of the detected serotypes, found that, according to previous outbreaks, the DENV-2 serotype has the capacity to produce severe cases, with approximately one-third of cases requiring hospitalization. 20 The co-circulation of more than one DENV serotype is one of the most important risk factors for the occurrence of severe cases in the population (Mulik, 2021). ¹⁹

The prevalence of dengue and the development of outbreaks in different regions depends on various factors such as climate change, weather events, and local infrastructure. In Veracruz, Mexico, cases of severe dengue fever increased following Hurricane Dean in 2007, Hurricane Ida in 2009, and Hurricane Ernesto in 2012, according to Hernández et al (2020). ¹¹

Del Carpio et al. identified that in Veracruz, since 2014, there has been an increase in dengue cases with the DENV-3 serotype, and in 2020, cases with atypical clinical presentations were observed, with patients presenting fever, arthralgia, headache, rash, respiratory symptoms, and liver damage. This serotype has been associated with severe dengue fever.

Currently, the country is experiencing a historically high number of dengue cases. In 2023, 42,203 cases have been confirmed, compared to 9,745 in 2022; 88 deaths have been confirmed, and 67% of the confirmed cases are from the states of Yucatán, Veracruz, Quintana Roo, Morelos, and Puebla. The increase in cases began at the end of 2022 in Quintana Roo and has now spread to the entire peninsula and southern Mexico. All four serotypes are circulating in most of these states, with the DENV-3 serotype predominating at up to 98% in Campeche, 95% in Yucatán, and 93% in Quintana Roo, which could be related to the high number of severe cases and deaths recorded.

According to official data from the General Directorate of Epidemiology, during the dengue outbreak in Sonora in 2022, the circulating serotypes were DENV-1, DENV-2, and DENV-3, with DENV-2 being the predominant serotype at 90%. In the southern part of the state, where the dengue cases began, this serotype was the most frequently identified, which could explain the 2.8% fatality rate of severe dengue cases. ²³

Further research into the behavior of dengue fever is necessary, given its nature as a vector-borne disease that is highly adaptable to climate change and urban environments. The potential for a new outbreak remains a latent risk. The limitations encountered in developing the clinical profile and identifying epidemiological factors were that only hospitalized patients were included, and the characteristics of cases that were treated on an outpatient basis are unknown. This is due to the type of patient population primarily served by the hospital. Future applications could include expanding the scope of research to other healthcare facilities, integrating facilities at all levels to better understand the disease's behavior in all its manifestations.

1. Díaz-Quiñonez JA. Risk of diseases transmitted by aedes mosquitoes in the metropolitan area of the valley of Mexico and the threat of syndemics in the country. Vol. 156, Gaceta Medica de Mexico. Academia Nacional de Medicina; 2020. p. 369– 71.

2. Wang WH, Urbina AN, Lin CY, Yang ZS, Assavalapsakul W, Thitithanyanont A, et al. Targets and strategies for vaccine development against dengue viruses. Biomedicine & Pharmacotherapy [Internet]. 2021;144:112304. Available from: https://www.sciencedirect.com/science/article/pii/S075333222101088X

3. Organización Mundial de la Salud. DENGUE, GUIAS PARA EL DIAGNÓSTICO, TRATAMIENTO, PREVENCIÓN Y CONTROL. Bolivia; 2009.

4. Dirección General de Epidemiología. Manual de procedimientos estandarizados para la vigilancia epidemiológica de las enfermedades transmitidas por vector. [Internet]. 2021 Aug [cited 2022 Nov 23]. Available from: https://epidemiologia.salud.gob.mx/gobmx/salud/documentos/manuales/36_Manual_ ETV.pdf

5. Ma E, Cheng G. Host immunity and vaccine development against Dengue virus. Infectious Medicine [Internet]. 2022;1(1):50–8. Available from: https://www.sciencedirect.com/science/article/pii/S2772431X2200003X

6. Carhuamaca Avalos AC, Hermoza Moquillaza RV, Arellano Sacramento C. Factores relacionados con la no prevención del dengue en un distrito de Lima, Perú, 2021. Revista de Investigación de la Universidad Norbert Wiener. 2022 May 20;11.

7. Prasad AK, Phukan AC, Barman B. A study on viral haemorrhagic fever due to dengue, chikungunya and Crimean Congo haemorrhagic fever virus among patients attending tertiary care hospital in North East India. Indian J Med Microbiol [Internet]. 2022;40(1):68–73. Available from: https://www.sciencedirect.com/science/article/pii/S0255085721046521

8. Chen Y, Li N, Lourenço J, Wang L, Cazelles B, Dong L, et al. Measuring the effects of COVID-19-related disruption on dengue transmission in southeast Asia and Latin America: a statistical modelling study. Lancet Infect Dis. 2022 May 1;22(5):657– 67.

9. Vasquez-Chavesta AZ, Morán-Mariños C, Rodrigo-Gallardo PK, Toro- Huamanchumo CJ. COVID-19 and dengue: Pushing the peruvian health care system over the edge. Travel Med Infect Dis. 2020 Jul 1;36:101808.

10. León-Figueroa DA, Abanto-Urbano S, Olarte-Durand M, Nuñez-Lupaca JN, Barboza JJ, Bonilla-Aldana DK, et al. COVID-19 and dengue coinfection in Latin America: A systematic review. New Microbes New Infect. 2022 Nov 1;49–50:101041.

11. Aguiar M, Anam V, Blyuss KB, Estadilla CDS, Guerrero B v., Knopoff D, et al. Mathematical models for dengue fever epidemiology: A 10-year systematic review. Phys Life Rev. 2022 Mar 1;40:65–92.

12. Thakali O, Raya S, Malla B, Tandukar S, Tiwari A, Sherchan SP, et al. Pilot study on wastewater surveillance of dengue virus RNA: Lessons, challenges, and implications for future research. Environmental Challenges. 2022 Dec 1;9.

13. Pan American Health Organization. Actualización epidemiológica semanal para dengue, chikunguña y zika en 2022 [Internet]. Washington, D.C.; 2022 Oct. Available from: https://www.paho.org/plisa

14. García Rodríguez G, Arturo Zaragoza Jiménez C, Yaneth Fortunata López Santiago D, Santa Elizabeth Ceballos Liceaga D, Carbajal Sandoval G, Antonio Padilla Monroy Armando Amezcua Jiménez Enf José Gilberto Moreno Castro M. Panorama epidemiológico del Dengue SE 46. Ciudad de México; 2022 Nov.

15. Gérardin P, Maillard O, Bruneau L, Accot F, Legrand F, Poubeau P, et al. Differentiating COVID-19 and dengue from other febrile illnesses in co-epidemics: Development and internal validation of COVIDENGUE scores. Travel Med Infect Dis. 2022 Jan 1;45:102232.

16. Hernández-García, E., Muñoz, M. de L., David, R. E., Pérez-Ramírez, G., Navarrete-Espinosa, J., Díaz-Badillo, Á., Domínguez-de-la-Cruz, E., Moreno-Galeana, Brito-Carreón, C. A. (2020). Epidemiological implications of the genetic diversification of dengue virus (DENV) serotypes and genotypes in Mexico. Infection, Genetics and Evolution.

17. Fonseca-Portilla, R., Martínez-Gil, M., & Morgenstern-Kaplan, D. (2021). Risk factors for hospitalization and mortality due to dengue fever in a Mexican population: a retrospective cohort study. International Journal of Infectious Diseases, 110.

18. Verma, P., Baskey, U., Choudhury, K. R., Dutta, S., Bakshi, S., Das, R., Mondal, P., Bhaduri, S., Majhi, D., Dutta, S., & Sadhukhan, P. C. (2023). Changing pattern of circulating dengue serotypes in the endemic region: An alarming risk to the healthcare system during the pandemic. Journal of Infection and Public Health, 16(12), 2046– 2057.

19. Mulik, V., Dad, N., & Buhmaid, S. (2021). Dengue in pregnancy: Review article. European Journal of Obstetrics and Gynecology and Reproductive Biology, 261.

20. Durand, S., Chavez, C., Vidal, C., Cervantes, G., & Cabezas, C. (2022). High frequency of severe dengue cases during the American/Asian DENV-2 lineage II epidemic in Peru. Anales de La Facultad de Medicina, 83(3).

21. Villamil-Gómez W. (2022). “Protocolo Diagnóstico Del Síndrome Febril Con Focalidad Respiratoria En Áreas Geográficas De Riesgo Endémico De Infecciones Tropicales.” Medicine - Programa De Formación Médica Continuada Acreditado pp. 3432–3437.

22. Chica, E., Artunduaga, G., Alexandra, M., Benavides, V., & Vargas, F. (n.d.). PEDIÁTRICO: FACTORES ASOCIADOS A SEVERIDAD DENGUE IN THE PEDIATRIC INTENSIVE CARE UNIT: FACTORS ASSOCIATED WITH SEVERITY.

23. Dirección General de Epidemiologia. Panorama Epidemiologico de Dengue: Semana epidemiológica 44 (2023). Nov 2023. Available from: https://www.gob.mx/cms/uploads/attachment/file/869715/Pano_dengue_44_2023.pdf

Vega-Medina M and Ruiz-Valdez Carmen A, Clinical characteristics and epidemiological factors of dengue in hospitalized patients, ERSJ 2025,1(2) 49-61