SARS-CoV-2 in a tropical area of Colombia, a remarkable conversion of presymptomatic to symptomatic people impacts public health.

BACKGROUND: The ability of SARS-CoV-2 to remain in asymptomatic individuals facilitates its dissemination and makes its control difficult. OBJECTIVE: To establish a cohort of asymptomatic individuals, change to the symptomatic status, and determine the most frequent clinical manifestations.  METHODS: Between April 9 and August 9, 2020, molecular diagnosis of SARS-CoV-2 infection was confirmed in 154 asymptomatic people in contact with subjects diagnosed with COVID-19. Nasopharyngeal swabs were performed on these people in different hospitals in Córdoba, the Caribbean area of Colombia. The genes E, RdRp, and N were amplified with RT-qPCR. Based on the molecular results and the Cq values, the patients were subsequently followed up through telephone calls to verify their health conditions. RESULTS: Overall, of 154 asymptomatic individuals, 103 (66.9%) remained asymptomatic, and 51 (33.1%) changed to symptomatic. The most frequent clinical manifestations in young people were anosmia and arthralgia. Adults showed cough, ageusia, and odynophagia; in the elderly were epigastralgia, dyspnea, and headache. Mortality was 8%. CONCLUSIONS: A proportion of 33% of presymptomatic individuals was found, of which four of them died. This high rate could indicate a silent transmission, contributing significantly to the epidemic associated with SARS-CoV-2.

Epidemiological and viral features of a cohort of SARS-CoV-2 symptomatic and asymptomatic individuals in an area of the Colombian Caribbean.

BACKGROUND: Severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) is an emerging viral pandemic disease. In the last 6 months, SARS-CoV-2 has caused millions of reported cases and hundreds of thousands of deaths. As other world regions, South America has not contained the pandemic's advance since it lacks the hospital and economic capacities. Public health implications of transmission, while the asymptomatic/presymptomatic infection is a critical concern at the current pandemic. OBJECTIVE: Describe the socio-demographic, clinical, and viral features of a cohort of SARS-CoV-2 infected individuals from the Colombian Caribbean. METHODS: Six hundred eighty-six clinical samples of suspected SARS-CoV-2 infection cases and contacts individuals from several hospital centers in the department of Córdoba, Colombia, were received at our laboratory between April 9th and May 16th, 2020. RNA was extracted using lysis buffers and spin columns. The samples were tested for SARS-CoV-2 by reverse transcription real-time polymerase chain reaction (RT-qPCR) using commercially available multiplex real-time PCR assay for simultaneous detection of 3 target genes of SARS-CoV-2 (Allplex™, 2019-nCoV assay, Korea). Viral copies quantification was done using a standard curve constructed from seriated dilutions of a SARS-CoV-2 positive control. Statics descriptive methods were used. RESULTS: Thirty-five nasopharyngeal samples were positive for SARS-CoV-2 infection; the average age was 43 (range, 1-95 years). Seventeen of 35 (49%) of the patients showed symptoms. Most of them had a cough, fever, and odynophagia; three of the patients reported having arthralgia. Only two patients required hospitalization. None of the patients had known co-morbidities. RT-qPCR results show that two of the symptomatic patients had significantly higher RNA copies than the rest. Eighteen of 35 (51%) individuals were asymptomatic, and the average age was 30 (range, 6-61 years). Four asymptomatic individuals showed a higher copy than some symptomatic patients; nonetheless, the average of RNA copies 8.26 × 1010 was lower than the symptomatic. CONCLUSIONS: This study shows that asymptomatic patients may develop infections with a high number of RNA copies. Since a considerable percentage of infections may be asymptomatic/presymptomatic, enhanced testing approaches may be needed to detect these persons. Due the occurrence of a large proportion of infections being a result from transmission originated in asymptomatic/presymptomatic individuals, public health interventions in Colombia should be based on two steps: a massive molecular screening, and viral load quantification. Finally, a remarkable issue in our study is the average age of symptomatic and asymptomatic groups (43 and 30 respectively) which may be important because of the economic impact that has been caused by the coronavirus pandemic and may be probably the cause of the reduced lethality observed in the country and the department at the time of this study.

Evaluation of serological test of Zika in an endemic area of flavivirus in the Colombian Caribbean.

The Zika virus (ZIKV) is an emerging flavivirus transmitted primarily through arthropods, endemic in Africa, Asia, and the Americas, and is considered a global threat by the World Health Organization. OBJECTIVE: To evaluate a commercial Zika virus test (IgG/IgM catalog number B815C, Biocan, Canada. METHODS: We evaluated 30 sera of patients diagnosed with Dengue, Leptospira, Malaria, Hantavirus, and Chikungunya. To establish the sensitivity of the test, two groups of sera were analyzed, the first one was patients with Zika RT-qPCR positive, and the second were patients RT-qPCR negative but with clinical suspicion of Zika. RESULTS: The specificity was of 23.3% (7/30), the sensitivity in acute patients with positive RT-qPCR was of 63.6%, the patients with clinical suspicion of Zika the sensitivity (IgM) was of 80% (n = 8/10). Overall sensitivity (IgM) of both groups was of 71.4% (15/21). CONCLUSIONS: The test showed a low specificity to be used as a serological test in an endemic area of flavivirus infection.

Case report: microcephaly associated with Zika virus infection, Colombia.

BACKGROUND: Recently there has been a large outbreak of Zika virus infections in Colombia, South America. The epidemic began in September 2015 and continued to April 2017, for the total number of Zika cases reported of 107,870. For those confirmed Zika cases, there were nearly 20,000 (18.5%) suspected to be pregnant women, resulting in 157 confirmed cases of microcephaly in newborns reported by their health government agency. There is a clear under-estimation of the total number of cases and in addition no prior publications have been published to demonstrate the clinical aspects of the Zika infection in Colombia. We characterized one Zika presentation to be able to compare and contrast with other cases of Zika infection already reported in the literature. CASE PRESENTATION: In this case report, we demonstrate congenital microcephaly at week 19 of gestation in a 34-year-old mother who showed symptoms compatible with Zika virus infection from Sincelejo, State of Sucre, in the Colombian Caribbean. Zika virus RNA was detected in the placenta using real-time reverse transcriptase polymerase chain reaction (RT-PCR). At week 25, the fetus weigh estimate was 770 g, had a cephalic perimeter of 20.2 cm (5th percentile), ventriculomegaly on the right side and dilatation of the fourth ventricle. At week 32, the microcephaly was confirmed with a cephalic perimeter of 22 cm, dilatation of the posterior atrium to 13 mm, an abnormally small cerebellum (29 mm), and an augmented cisterna magna. At birth (39 weeks by cesarean section), the head circumference was 27.5 cm, and computerized axial tomography (Siemens Corp, 32-slides) confirmed microcephaly with calcifications. CONCLUSION: We report a first case of maternal Zika virus infection associated with fetal microcephaly in Colombia and confirmed similar presentation to those observed previous in Brazil, 2015-2016.

Leptospirosis in pigs, dogs, rodents, humans, and water in an area of the Colombian tropics.

Leptospirosis is a reemerging zoonosis of global distribution and is one of the causes of hemorrhagic fevers in the tropics. We sought to determine seroprevalence in humans and animals and isolate Leptospira interrogans sensu lato in domestic animals, rodents, and water sources. The study was conducted in a tropical area of the middle Sinú in Cordoba, Colombia. In a prospective descriptive study, we collected blood and urine from pigs and dogs, sera from rural human workers, sera and kidney macerates of rodents, and water samples from environmental sources. We used microagglutination to screen for antibodies to 13 serovars. Strains were cultured on the Ellinghausen-McCullough-Johnson-Harris medium and confirmed by PCR amplifying lipL32 gene. Seroprevalence was 55.9% in pigs, 35.2% in dogs, and 75.8% in humans; no antibody was detected, and no Leptospira were isolated from kidney macerates of rodents. Seven L. interrogans sensu lato strains were isolated: three from pigs, two from dogs, and two from water. High seroprevalence in pigs, dogs, and humans, concomitant to isolation of strains, demonstrates that in Cordoba, transmission exists among animals, the environment, and humans, which warrants the implementation of public health intervention measures to reduce the epidemiological impact of leptospirosis in the region.

Hard ticks (Ixodida: Ixodidae) in the Colombian Caribbean harbor the Jingmen tick virus: an emerging arbovirus of public health concern.

BACKGROUND: Ticks are obligate hematophagous ectoparasites involved in transmitting viruses of public health importance. The objective of this work was to identify the Jingmen tick virus in hard ticks from the Colombian Caribbean, an arbovirus of importance for public health. METHODS: Ticks were collected in rural areas of Córdoba and Cesar, Colombia. Taxonomic identification of ticks was carried out, and pools of 13 individuals were formed. RNA extraction was performed. Library preparation was performed with the MGIEasy kit, and next-generation sequencing (NGS) with MGI equipment. Bioinformatic analyses and taxonomic assignments were performed using the Galaxy platform, and phylogenetic analyses were done using IQ-TREE2. RESULTS: A total of 766 ticks were collected, of which 87.33% (669/766) were Rhipicephalus microplus, 5.4% (42/766) Dermacentor nitens, 4.2% (32/766) Rhipicephalus linnaei, and 3.0% (23/766) Amblyomma dissimile. Complete and partial segments 1, 2, 3, and 4 of Jingmen tick virus (JMTV) were detected in the metatranscriptome of the species R. microplus, D. nitens, and A. dissimile. The JMTVs detected are phylogenetically related to JMTVs detected in Aedes albopictus in France, JMTVs detected in R. microplus in Trinidad and Tobago, JMTVs in R. microplus and A. variegatum in the French Antilles, and JMTVs detected in R. microplus in Colombia. Interestingly, our sequences clustered closely with JMTV detected in humans from Kosovo. CONCLUSIONS: JMTV was detected in R. microplus, D. nitens, and A. dissimile. JMTV could pose a risk to humans. Therefore, it is vital to establish epidemiological surveillance measures to better understand the possible role of JMTV in tropical diseases.

Case Report: A Case of Sepsis due to Shewanella algae Infection in the Colombian Caribbean.

Shewanella algae is an opportunistic Gram-negative bacillus that inhabits marine ecosystems and can cause sepsis in humans. This case report describes an 80-year-old obese woman with liver cirrhosis who presented with neurological and respiratory impairment. Shewanella algae were isolated in the blood cultures. Due to age and comorbidities, sepsis could be the cause of the patient's fatal outcome. Shewanella algae infection is a risk for immunocompromised people in the tropics.

Seroprevalence of antibodies against to SARS-CoV 2 in umbilical cord blood in two hospital centers in Córdoba and Sucre, Colombia.

INTRODUCTION: Pregnant women continue to be vulnerable to COVID-19, and their immunosuppressed state could put them at greater risk of developing more severe forms of the disease. In Colombia and Latin America, there are few studies on the immune response of the newborn against SARS-CoV-2. AIM: To determine the prevalence of SARS-CoV-2 infection in umbilical cord blood in two hospital centers in Córdoba and Sucre. METHODS: Between March and June 2021, a prospective descriptive cross-sectional study was carried out. Two hospitals from the departments of Córdoba and Sucre, located in the Northwest Caribbean area of Colombia, participated. Three hundred sixty umbilical cord blood samples were taken at the two hospitals. A commercial ELISA was performed to detect total IgG, IgM, and IgA antibodies against the N protein of SARS-CoV-2. The ethics committee approved the study of the participating institutions. RESULTS: Of 3.291 women who gave birth in the hospital centers included in the study, 360 (11%) participated. Complete clinical data were obtained for 223 women. The mean age of the women was 24 years (range, 15-42). 29.4% (106/360) of the umbilical cord samples had total antibodies against SARS-CoV-2. Pregnant women did not have blood samples taken. 58% of the women were asymptomatic. There was no association between umbilical cord samples, clinical, epidemiological characteristics, and serological response to antibodies to SARS-CoV-2 (p > 0.05). CONCLUSIONS: The prevalence of umbilical cord blood samples was 29.4% for total SARS-CoV-2 antibodies. The study provides essential aspects for the epidemiological approach to neonates infected with SARS-CoV-2.

Immunogenicity and safety of a RBD vaccine against SARS-CoV-2 in a murine model.

INTRODUCTION: Although more than half of the world's population is already vaccinated, the appearance of new variants of concern puts public health at risk due to the generation of new immunogens against the virus as a crucial and relevant strategy in the control of these new variants. METHODS: A preclinical study used a potential vaccine candidate (RBD, SARS-CoV-2). Four groups of BALB/c mice were used, a control group, an adjuvant group, a group inoculated with one dose of RBD subunit protein, and the fourth group inoculated with two doses of RBD subunit protein. RESULTS: No inflammatory or cellular changes were shown in the mice's anatomopathological evaluation. Higher kinetics and 75% seroconversion were obtained in the mice inoculated with two doses of RBD (P < 0.0001). CONCLUSIONS: The application of two doses of the RBD vaccine candidate in BALB/c mice proved safe and immunogenic against SARS-CoV-2.

Human-to-dog transmission of SARS-CoV-2, Colombia.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the causative agent of the current COVID-19 pandemic, has evolved to have a wide range of hosts, including non-human primates, wild and domestic animals. The ACE2 protein has a high level of conservation and is the common receptor invertebrate species for a viral infection to occur; this receptor could give rise to anthroponotic events. This article describes the first event of symptomatic transmission in Latin America from a human to a dog by the B.1.625 lineage of SARS-CoV-2. We found 21 shared mutations in the complete genomes of viral sequences from owners and dogs. Further phylogenetic and molecular analysis showed that 100% co-localization of the clade helps to understand human-animal transmission. Prediction of the Spike protein structure of the sequenced virus and docking analyzes showed that the E484K mutation in the receptor-binding domain (RBD) could contribute to the viral affinity of dACE2. Therefore, close contact between SARS-CoV-2-infected humans and pets should be avoided to prevent the emergence of novel mutations of public health importance from anthroponotic events.

"One feels anger to know there is no one to help us!". Perceptions of mothers of children with Zika virus-associated microcephaly in Caribbean Colombia: A qualitative study.

BACKGROUND: The epidemic of Zika virus (ZIKV) was associated with a sudden and unprecedented increase in infants born with microcephaly. Colombia was the second most affected country by the epidemic in the Americas. Primary caregivers of children with ZIKV-associated microcephaly, their mothers mainly, were at higher risk of suffering anxiety and depression. Often, these women were stigmatized and abandoned by their partners, relatives, and communities. METHODOLOGY/PRINCIPAL FINDINGS: This study aimed to understand the perceptions about ZIKV infection among mothers of children born with microcephaly during the ZIKV epidemic in Caribbean Colombia, and the barriers and facilitators affecting child health follow-up. An exploratory qualitative study, based on Phenomenology and Grounded Theory, was conducted in Caribbean Colombia. Data were collected through In-Depth Interviews (IDI) from women who delivered a baby with microcephaly during the ZIKV epidemic at Clínica Salud Social, Sincelejo, Sucre District (N = 11). The themes that emerged during the interviews included experiences from their lives before pregnancy; knowledge about ZIKV; experiences and perceptions when diagnosed; considering a possible termination of pregnancy, and children's clinical follow-up. In some cases, women reported having been told they were having a baby with microcephaly but decided not to terminate the pregnancy; while in other cases, women found out about their newborn's microcephaly condition only at birth. The main barriers encountered by participants during children's follow-up included the lack of psychosocial and economic support, the stigmatization and abandonment by some partners and relatives, and the frustration of seeing the impaired development of their children. CONCLUSIONS: This study contributed to identifying the social, medical, psychological, and economic needs of families with children affected by the ZIKV epidemic. Commitment and action by local and national governments, and international bodies, is required to ensure sustained and quality health services by affected children and their families.

SARS-CoV-2 in eight municipalities of the Colombian tropics: high immunity, clinical and sociodemographic outcomes.

BACKGROUND: Serological evaluation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an alternative that allows us to determine the prevalence and dynamics of this infection in populations. The goal of this study was to determine the clinical and sociodemographic dynamics of SARS-CoV-2 infection in a region of the Colombian Caribbean. METHODS: Between July and November 2020, a cross-sectional observational study was carried out in Córdoba, located in northeast Colombia in the Caribbean area. Eight municipalities with the largest populations were chosen and 2564 blood samples were taken. A commercial enzyme-linked immunosorbent assay was used with the recombinant protein antigen N of SARS-CoV-2. The people included in the study were asked for sociodemographic and clinical data, which were analysed by statistical methods. RESULTS: A seroprevalence of 40.8% was obtained for SARS-CoV-2 in the Córdoba region. In the bivariate analysis, no differences were observed in seropositivity against SARS-CoV-2 for gender or age range (p>0.05). Higher seropositivity was found in low socio-economic status and symptomatic patients (p<0.0001). A total of 30.7% of the asymptomatic patients were seropositive for SARS-CoV-2, which could be linked to the spread of this infection. In the multivariate analysis, seroconversion was related to poverty and clinical manifestations such as anosmia and ageusia (p<0.05). CONCLUSIONS: The high seropositivity in Córdoba is due to widespread SARS-CoV-2 in this population. The relationship between seropositivity and socio-economic status suggests a higher exposure risk to the virus caused by informal economic activities in low-income groups. Clinical manifestations such as anosmia and ageusia could be clinical predictors of infection by the new emergent coronavirus.

Perceptions and Emotional State of Mothers of Children with and without Microcephaly after the Zika Virus Epidemic in Rural Caribbean Colombia.

Zika virus (ZIKV) infection during pregnancy can cause neurological manifestations such as microcephaly. The aim of this study was to explore perceptions of ZIKV and mental health in women exposed to ZIKV during pregnancy in Colombia. This was a mixed-methods study based on structured interviews and psychological tests. Structured interviews were transcribed and analysed with Atlas Ti software. A grounded theory approach was applied. Quantitative analysis was performed with Statistical Package for Social Science, SPSS, V. 20. The study was approved by the Ethics Committee of the Universidad de Córdoba, Montería. Seventeen women participated in the study; nine of them were mothers of children with microcephaly. Maternal age ranged from 16 to 41 years old. The main themes discussed during interviews were: feelings, support, sources of information, and consequences on children's health. Women with children affected by microcephaly showed worse mental health compared to women with normocephalic children. Maternal mental health worsened after 24 months from giving birth. Perceptions regarding disease severity and lack of knowledge were considered to affect maternal mental health. Social support and spirituality were key determinants for caregivers. Future research is needed to further study coping mechanisms and mental health outcomes over time by affected populations.

High Seroprevalence of Antibodies against Arboviruses among Pregnant Women in Rural Caribbean Colombia in the Context of the Zika Virus Epidemic.

Mosquito-borne viruses such as dengue (DENV), chikungunya (CHIKV), and Zika (ZIKV) have spread in recent decades. We aimed to assess seroprevalence of arboviral infections in pregnant women living in Cereté, Caribbean Colombia. In 2016 a cross-sectional facility-based sero-survey study was performed among pregnant women (N = 90). Most of them (66%) reported at least one symptom or sign compatible with arboviral infection over the previous 15 days. All screened women had a positive IgG for DENV, 89% for ZIKV, and 82% for CHIKV. One woman tested positive for ZIKV IgM. This study shows the high exposure among pregnant women to arboviruses in endemic areas, shown by the high seroprevalence of past arboviral infections. Given the evidence on the potential risks of these arboviral infections on pregnancy and infant outcomes, these results highlight the need for continuous epidemiological surveillance of arboviral diseases, particularly among those most of risk of their harmful consequences.

Acceptability of a Hypothetical Zika Vaccine among Women from Colombia and Spain Exposed to ZIKV: A Qualitative Study.

Zika virus (ZIKV) can cause pregnancy loss and congenital Zika syndrome, among other poor health outcomes. The ZIKV epidemic in 2015-2017 disproportionately affected pregnant women in poor-resource settings. We aimed to understand perceptions and attitudes towards a hypothetical ZIKV vaccine, women's willingness to be vaccinated, and potential barriers and facilitators for vaccine acceptance in 1) migrant women living in Spain who travelled to their countries of origin and were diagnosed with ZIKV infection during pregnancy, and their healthcare providers, and 2) women living in Colombia who delivered a child with microcephaly. An exploratory qualitative study based on phenomenology and grounded theory was conducted. Data were collected through in-depth, paired and semi-structured interviews. Overall, women from both sites were willing to receive a hypothetical ZIKV vaccine. However, some expressed concerns of being vaccinated during pregnancy, yet they would accept it if the vaccine was recommended by a healthcare professional they trust. Main fears towards vaccination were related to vaccine safety and potential adverse effects on child's health. Women reported feeling hesitant to participate in a ZIKV vaccine trial. These results may contribute to guiding the effective delivery of future ZIKV vaccines among populations most at risk and particularly vulnerable.

Severe Acute Respiratory Syndrome Coronavirus 2 Seroprevalence Among Adults in a Tropical City of the Caribbean Area, Colombia: Are We Much Closer to Herd Immunity Than Developed Countries?

A serological survey was carried out in Monteria (500 000 population), a mid-size city in Colombia. An overall prevalence of 55.3% (95% confidence interval, 52.5%-57.8%) was found among a sample of 1.368 people randomly selected from the population. Test positivity was related to economic characteristics with the highest prevalence found in the most impoverished areas, representing 83.8% of the city's population. We found a prevalence that might be associated with some important level of population immunity.

Serological cross-reactivity using a SARS-CoV-2 ELISA test in acute Zika virus infection, Colombia.

OBJECTIVES: We investigated seroreactivity by using a commercial SARS-CoV-2 ELISA test in samples collected from different groups of individuals, including patients diagnosed to have Dengue, Zika, and Chikungunya infection between 2015 and 2019, from an endemic area in the Caribbean Colombian region. METHODS: A total of 127 sera samples obtained from six different groups of individuals were included in this study: Group A: patients with confirmed SARS-CoV-2 infection; Group B: patients with symptoms suggestive of COVID-19 or asymptomatic contacts with confirmed patients; Group C: patients with acute or recent dengue virus infection; Group D: patients with acute Zika virus infection; Group E: patients with previous Chikungunya virus infection; and Group F: individuals with exposure to spotted fever group rickettsiae. RESULTS: Overall, group A, group B, and group D showed seroreactivity to SARS-CoV-2 in 92%, 75%, and 26% of samples, respectively; furthermore, group C, group E, and group F showed 100% seronegativity. CONCLUSIONS: We found 26% of serological cross-reactivity in patients with acute Zika virus infection by using a commercial SARS-CoV-2 ELISA test. Further studies are needed to evaluate whether serological cross-reaction is maintained with time in nonacute patients with previous exposure to the Zika virus and its effect in SARS-CoV-2 serosurveys in endemic areas for this arbovirus.

Genomic epidemiology of Chikungunya virus in Colombia reveals genetic variability of strains and multiple geographic introductions in outbreak, 2014.

Chikungunya virus (CHIKV) is considered a public health problem due to its rapid spread and high morbidity. This study aimed to determine the genetic diversity and phylogenetic relationships of CHIKVs in Colombia. A descriptive and retrospective study was carried out using sera of patients infected with Chikungunya during the outbreak in Colombia. The whole genomes of CHIKV (n = 16) were sequenced with an Illumina Hi-seq 2500 and were assembled using the Iterative Virus Assembler software. A Bayesian inference phylogenetic analysis was carried out with 157 strains of worldwide origin. The Colombian CHIKV sequences were grouped in the Asian genotype; however, three independent phylogenetic subclades were observed, probably the result of three separate introductions from Panama, Nicaragua, and St. Barts. Each subclade showed several different non-synonymous mutations (nsP2-A153V; nsp2-Y543H; nsp2-G720A; nsP3-L458P; Capside R78Q), that may have functional consequences for CHIKV biology and pathogenesis. These same mutations may affect the efficacy of potential CHIKV vaccines.

Lessons learned of emerging Chikungunya virus in two populations of social vulnerability of the Colombian tropics: epidemiological analysis.

BACKGROUND: Notwithstanding the strong epidemiological impact of the Chikungunya in the Colombian Caribbean, in 2014, not the entire population were affected in the same way. This study describe the demographic, socio-economic, clinical and epidemiological aspects of the de Chikungunya in Ovejas and Corozal, two neighboring municipalities with high vulnerability in health in the Colombian Caribbean. METHODS: A cross-sectional study was performed in February 2015. A convenience sampling was carried out in 971 families affected with chikungunya. Also, a socio-demographics, clinical and epidemiological questionnaire was carried out for people who met the definition of suspected Chikungunya clinical case. For the statistical analysis, data and variables, frequencies, proportions and means were compared in the two municipalities studied. A logistic regression model was constructed to explain the effect of factors studied on the risk of family infection (RFI) or likelihood of contagion within each household. Was used the software EpiInfo 7.2.2.2 and a significance level with p-value < 0.05. RESULTS: In Ovejas, 516 households were affected by Chikungunya, 48% (1269/2631) of their inhabitants became sick; in Corozal, 455 families were affected and 42% (839/1999) of their members became sick. The evolution of the epidemic curves of Chikungunya outbreak was different in the two studied areas, the disease was more aggressive in Ovejas. Ten variables were pre-selected by univariate analysis to explain the RFI by Chikungunya, and were integrated into a logistic regression model. The final model was constructed with the following variables: municipality, gender, occupation, family income, use of repellent and fumigation. The logistic model was assessed as appropriate; however, the biases in the selection of the surveyed dwellings and in the selection of symptomatic patients could influence the results. CONCLUSIONS: It was demonstrated the epidemiological complexity of Chikungunya and the serious problem caused in populations with high vulnerability in health. The accurate association observed in the logistic regression model suggests the role of the factors studied as determinant in the rate of infection of the Chikungunya; coverage problems and surveillance in health care, demographic aspect, socio-economic problems and lack of preventive measures could explains the risk of family infection by Chikungunya in some areas tropics of Colombia. TRIAL REGISTRATION: number approval 007-2016 ethics committee-IIBT.