Incidence Of Dengue Virus Infection Research Articles

PENGETAHUAN, KUALITAS HIDUP DAN BIAYA SAKIT PASIEN DENGUE DI RS PKU MUHAMMADIYAH GAMPING

The incidence of dengue virus infection in the D.I. Yogyakarta reached 3,618 cases in 2020. Based on its clinical manifestations, dengue virus infection is divided into Dengue Fever (DF), Dengue Haemorrhagic Fever (DHF), and Dengue Shock Syndrome (DSS). This study aims to identify the level of knowledge, quality of life, and costs of dengue patients at PKU Muhammadiyah Gamping Hospital from March 2021 to October 2021. This study used a cross-sectional design. The measurement of the patient's knowledge level used a questionnaire knowledge of dengue, while the quality of life was assessed using EQ-5D-5L for adult patients and EQ-5D-Y for pediatric patients. The cost of illness data from the hospital finance database. This study involved 31 respondents with the characteristics aged 16-40 years (54.84%), male (87.1%), using BPJS insurance (80.65%), and an average length of stay of 4 days (51.61%). The patient's level of knowledge about dengue, knowledge of dengue prevention, and dengue prevention behavior reached 74.20% (sufficient), 74.20% (sufficient), and 77.42% (sufficient) respectively. The quality of life of dengue patients reached 100% and 85.2% in DF patients, while the DHF patients felt a few anxious/depressed (sad). The average cost of illness in DF patients was Rp. 2,796,386 and Rp. 3,378,537 in DHF patients.

Distribution of Dengue Virus Serotypes during the COVID 19 Pandemic in Sri Lanka

Background: Dengue virus (DENV) infection is highly endemic in Sri Lanka with frequent epidemics. Knowledge on DENV serotype distribution will provide important information on impending epidemics. Understanding the disease burden of DENV infection during COVID-19 pandemic is highly important. Objective: To analyze the incidence of DENV infection and serotype distribution among clinically suspected patients with DENV infection during COVID-19 pandemic in Sri Lanka. Study design: This retrospective study analyzed 1796 plasma samples from patients with clinically suspected DENV infection received at Medical Research Institute (MRI), for testing of DENV RNA, from May 2019 to April 2021. Detection of viraemia and serotypes was performed using a commercially-validated serotyping real time Reverse Transcriptase Polymerase Chain Reaction (RT-PCR). Demographic and clinical details were recruited from accompanying request forms. Results were analyzed using descriptive statistics and chi square testing. Results: Of the samples 69.2% (n=1243) became positive for DENV RNA with 55.34% (n=688) belonging to patients under 16 years and 20.99% (n=261) to patients with severe infection. The vireamic rate ranged from 31.9% to 80.12% during different quarters of the study period. DENV-2 was detected in 40.2% (n=500) followed by DENV-3(37.97%, n=472) and DENV-1(15.44%, n=192) while co-infection with two different serotypes was observed in 5.79% (n=72). DENV- 3(47.5%, n=124) and DENV-2(39.46%, n=103) exhibited high percentage of positivity among patients with severe infection. Conclusions: Incidence of Dengue virus infection in Sri Lanka showed a noticeable decrease during study period. DENV-2 and DENV-3 exhibited dominance with re-emergence of DENV-1 and co- infection with multiple serotypes. DENV-2 and DENV-3 were detected with severe infection predominantly.

Dengue Seroprevalence and Factors Associated with Dengue Seropositivity in Petaling District, Malaysia.

Dengue virus (DENV) infection is a major public health concern, posing huge economic and disease burdens globally. In Malaysia, the incidence of DENV infections has increased significantly over the years. Nevertheless, the passive surveillance mechanism applied may not capture the actual magnitude of DENV infection. There was also a paucity of community-based studies exploring DENV seroprevalence. This study aimed to determine the DENV seroprevalence and the associated factors among the urban population in Petaling district, Malaysia. A population-based cross-sectional study was conducted from 18 August to 26 October 2018 with 533 participants recruited. Blood samples were collected and analysed for DENV seropositivity using a composite reference standard comprised of three dengue serological tests. Associated factors were identified by fitting Generalised Linear Mixed Models with binomial error structure and logit link function. DENV seroprevalence obtained was 79.0% (95% CI: 75.2–82.4%). The age-specific DENV seroprevalence showed an increasing trend with advancing age, from 22.7% (95% CI: 9.6–45.0%) for those aged below five years old to 94.9% (95% CI: 81.3–98.7%) for those aged ≥60 years old. Only age group and house level were found to be significant factors associated with DENV seropositivity. The odds of being DENV seropositive generally increased with age, from 13.43 (95% CI: 2.77–65.22) for the 5–9 years old age group to 384.77 (95% CI: 39.27–3769.97) for the ≥60 years old age group, as compared to those aged below 5 years old. For house level, those who lived on the first and second floor (OR: 8.98, 95% CI: 3.16–25.12) and the third floor and above (OR: 4.82, 95% CI: 1.89–12.32) had greater odds of being DENV seropositive compared to those living on the ground floor. This study demonstrated the persistently high DENV seroprevalence among the urban population in Petaling district, which could be useful to evaluate dengue control measures taken and estimate more accurate disease incidence. The associated factors with DENV seropositivity identified could also contribute to undertaking more targeted preventive and control measures.

Viral Parkinsonism: An underdiagnosed neurological complication of Dengue virus infection.

Dengue virus (DENV) is a flavivirus that is a significant cause of human disease costing billions of dollars per year in medical and mosquito control costs. It is estimated that up to 20% of DENV infections affect the brain. Incidence of DENV infections is increasing, which suggests more people are at risk of developing neurological complications. The most common neurological manifestations of DENV are encephalitis and encephalopathy, and movement disorders such as parkinsonism have been observed. Parkinsonism describes syndromes similar to Parkinson’s Disease where tremors, stiffness, and slow movements are observed. Parkinsonism caused by viral infection is characterized by patients exhibiting at least two of the following symptoms: tremor, bradykinesia, rigidity, and postural instability. To investigate DENV-associated parkinsonism, case studies and reports of DENV-associated parkinsonism were obtained from peer-reviewed manuscripts and gray literature. Seven reports of clinically diagnosed DENV-associated parkinsonism and 15 cases of DENV encephalitis, where the patient met the case criteria for a diagnosis of viral parkinsonism were found. Clinically diagnosed DENV-associated parkinsonism patients were more likely to be male and exhibit expressionless face, speech problems, and lymphocytosis. Suspected patients were more likely to exhibit tremor, have thrombocytopenia and low hemoglobin. Viral parkinsonism can cause a permanent reduction in neurons with consequential cognitive and behavior changes, or it can leave a latent imprint in the brain that can cause neurological dysfunction decades after recovery. DENV-associated parkinsonism is underdiagnosed and better adherence to the case definition of viral parkinsonism is needed for proper management of potential sequalae especially if the patient has an ongoing or potential to develop a neurodegenerative disease.

Aggressive organ penetration and high vector transmissibility of epidemic dengue virus-2 Cosmopolitan genotype in a transmission mouse model.

Dengue virus (DENV) causes dengue fever and severe hemorrhagic fever in humans and is primarily transmitted by Aedes aegypti and A. albopictus mosquitoes. The incidence of DENV infection has been gradually increasing in recent years due to global urbanization and international travel. Understanding the virulence determinants in host and vector transmissibility of emerging epidemic DENV will be critical to combat potential outbreaks. The DENV serotype 2 (DENV-2), which caused a widespread outbreak in Taiwan in 2015 (TW2015), is of the Cosmopolitan genotype and is phylogenetically related to the virus strain linked to another large outbreak in Indonesia in 2015. We found that the TW2015 virus was highly virulent in type I and type II interferon-deficient mice, with robust replication in spleen, lung, and intestine. The TW2015 virus also had high transmissibility to Aedes mosquitoes and could be effectively spread in a continuous mosquitoes-mouse-mosquitoes-mouse transmission cycle. By making 16681-based mutants carrying different segments of the TW2015 virus, we identified the structural pre-membrane (prM) and envelope (E) genes as key virulence determinants in the host, with involvement in the high transmissibility of the TW2015 virus in mosquitoes. The transmission mouse model will make a useful platform for evaluation of DENV with high epidemic potential and development of new strategies against dengue outbreaks.

Molecular evolution of dengue virus types 1 and 4 in Korean travelers

Dengue virus (DV) is a mosquito-borne virus that is endemic to many tropical and subtropical areas. Recently, the annual incidence of DV infection has increased worldwide, including in Korea, due to global warming and increased global travel. We therefore sought to characterize the molecular and evolutionary features of DV-1 and DV-4 isolated from Korean overseas travelers. We used phylogenetic analysis based on the full coding region to classify isolates of DV-1 in Korea into genotype I (43251, KP406802), genotype IV (KP406803), and genotype V (KP406801). In addition, we found that strains of DV-4 belonged to genotype I (KP406806) and genotype II (43257). Evidence of positive selection in DV-1 strains was identified in the C, prM, NS2A, and NS5 proteins, whereas DV-4 showed positive selection only in the non-structural proteins NS2A, NS3, and NS5. The substitution rates per site per year were 5.58 × 10-4 and 6.72 × 10-4 for DV-1 and DV-4, respectively, and the time of the most recent common ancestor was determined using the Bayesian skyline coalescent method. In this study, the molecular, phylogenetic, and evolutionary characteristics of Korean DV-1 and DV-4 isolates were evaluated for the first time.

Association of serologic and hematologic test results in dengue infant patients in RSUP. Dr. Hasan Sadikin Bandung

The incidence of Dengue virus infection is increasing every year,and the progression of the disease is faster towards severe manifestations in infants than in children and adults.The clinical appearance is still challenging to make for the diagnosis of dengue fever, so routine blood examination becomes one of thefurther enforcement efforts. The gold standard isconfirmatory tests for dengue, but this examination would be difficult in remote areas and also cost more. Research on serological testing and its association with routine blood testing in infant dengue-infected patients is still less publicized. The purpose of this study was to describe theconnection between serological and routine blood test results of infant dengue infection patients in RSUP Dr. Hasan Sadikin. Observational design in dengue 56 infants with 2-12 months age range examined serologic test and routine blood examination. The results showed that serological testing tended to be on routine blood tests. It can be from differences in routine blood tests such as hemoglobin, hematocrit, and platelets. Also, there was also no difference in routine blood profile between reactive and non-reactive IgM groups. It suggests that routine blood examination results are still lacking for the diagnosis of dengue.

Ability To Serologically Confirm Recent Zika Virus Infection in Areas with Varying Past Incidence of Dengue Virus Infection in the United States and U.S. Territories in 2016.

Cross-reactivity within flavivirus antibody assays, produced by shared epitopes in the envelope proteins, can complicate the serological diagnosis of Zika virus (ZIKAV) infection. We assessed the utility of the plaque reduction neutralization test (PRNT) to confirm recent ZIKAV infections and rule out misleading positive immunoglobulin M (IgM) results in areas with various levels of past dengue virus (DENV) infection incidence. We reviewed PRNT results of sera collected for diagnosis of ZIKAV infection from 1 January through 31 August 2016 with positive ZIKAV IgM results, and ZIKAV and DENV PRNTs were performed. PRNT result interpretations included ZIKAV, unspecified flavivirus, DENV infection, or negative. For this analysis, ZIKAV IgM was considered false positive for samples interpreted as a DENV infection or negative. In U.S. states, 208 (27%) of 759 IgM-positive results were confirmed to be ZIKAV compared to 11 (21%) of 52 in the U.S. Virgin Islands (USVI), 15 (15%) of 103 in American Samoa, and 13 (11%) of 123 in Puerto Rico. In American Samoa and Puerto Rico, more than 80% of IgM-positive results were unspecified flavivirus infections. The false-positivity rate was 27% in U.S. states, 18% in the USVI, 2% in American Samoa, and 6% in Puerto Rico. In U.S. states, the PRNT provided a virus-specific diagnosis or ruled out infection in the majority of IgM-positive samples. Almost a third of ZIKAV IgM-positive results were not confirmed; therefore, providers and patients must understand that IgM results are preliminary. In territories with historically higher rates of DENV transmission, the PRNT usually could not differentiate between ZIKAV and DENV infections.

Evaluation of Active RT-PCR (NS1 Ag Assay) Compound for Dengue Haemorrhagic Fever (Aedes aegypti sp).

The global prevalence of dengue cases has increased in India. The increasingly widespread distribution and the rising incidence of dengue virus infections are related to increased distribution of Aedes aegypti, an increasingly urban population, and increasing air travel. Several countries show that the age of the reported dengue cases has increased from 5-12 years, to older children and young adults. Although shock and plasma leakage seem to be more prevalent as age decreases, the frequency of internal hemorrhage rises as age increases. Increase in liver enzymes found in both children and adults indicated liver involvement during dengue infections. Pre-existing liver diseases in adults such as chronic hepatitis, alcoholic cirrhosis, and hemoglobinopathies may aggravate the liver impairment in dengue infection. Fulminant hepatitis is a rare but well described problem in adult patients with dengue infection. Currently, no specific therapeutic agent exists for dengue. The early recognition of dengue infection, bleeding tendency, and signs of circulatory collapse would reduce mortality rates in adult patients with dengue infection.

Incidence of Dengue Virus Infection in Adults and Children in a Prospective Longitudinal Cohort in the Philippines.

BackgroundThe mean age of dengue has been increasing in some but not all countries. We sought to determine the incidence of dengue virus (DENV) infection in adults and children in a prospective cohort study in the Philippines where dengue is hyperendemic.Methodology/Principal FindingsA prospective cohort of subjects ≥6 months old in Cebu City, Philippines, underwent active community-based surveillance for acute febrile illnesses by weekly contact. Fever history within the prior seven days was evaluated with an acute illness visit followed by 2, 5, and 8-day, and 3-week convalescent visits. Blood was collected at the acute and 3-week visits. Scheduled visits took place at enrolment and 12 months that included blood collections. Acute samples were tested by DENV PCR and acute/convalescent samples by DENV IgM/IgG ELISA to identify symptomatic infections. Enrolment and 12-month samples were tested by DENV hemagglutination inhibition (HAI) assay to identify subclinical infections. Of 1,008 enrolled subjects, 854 completed all study activities at 12 months per-protocol undergoing 868 person-years of surveillance. The incidence of symptomatic and subclinical infections was 1.62 and 7.03 per 100 person-years, respectively. However, in subjects >15 years old, only one symptomatic infection occurred whereas 27 subclinical infections were identified. DENV HAI seroprevalence increased sharply with age with baseline multitypic HAIs associated with fewer symptomatic infections. Using a catalytic model, the historical infection rate among dengue naïve individuals was estimated to be high at 11–22%/year.Conclusions/SignificanceIn this hyperendemic area with high seroprevalence of multitypic DENV HAIs in adults, symptomatic dengue rarely occurred in individuals older than 15 years. Our findings demonstrate that dengue is primarily a pediatric disease in areas with high force of infection. However, the average age of dengue could increase if force of infection decreases over time, as is occurring in some hyperendemic countries such as Thailand.

Incidence of dengue virus infections in febrile episodes in Ile-Ife, Nigeria

Background: Dengue viruses have been identified as the most important arboviral pathogen in the world. They are transmitted by mosquitoes of Aedes species. While dengue infection is accompanied by little or no subclinical signs in many, about 1-2% may produce clinically severe Dengue Haemorrhagic Fever/Dengue Shock Syndrome. Early recognition, appropriate treatment and elimination of mosquito vectors will help control it. The study is aimed at determining the incidence of dengue infections in Ile-Ife.Materials and Methods: Three millilitres venous blood was collected from each of one hundred and seventy nine patients presenting with fever in the last two weeks, and analyzed for the presence of anti-dengue IgM antibodies using Dengue Virus IgM ELISA kit (DIA.PRO, Italy) according to the manufacturer’s instructions while the results and demographic data were analyzed using SPSS version 16.Results: It was observed that 46 (25.7%) of the 179 had detectable IgM antibodies to dengue virus with 9 of them having no detectable malaria parasite. The incidence was 26.5% and 25% in male and female respectively. Further studies will be necessary to confirm the relatedness of blood transfusion as an important risk factor to the transmission of dengue virus.Conclusion: The study established the presence of fresh dengue infections for the first time in Ile-Ife among different groups of people. Clinicians are advised to prioritize laboratory diagnosis, especially of fever.Key words: Dengue, Dengue shock, Flaviviridae, ELISA, IgM

Incidence of dengue virus infection in school-aged children in Puerto Rico: a prospective seroepidemiologic study.

Dengue is a potentially fatal acute febrile illness caused by the mosquito-borne dengue viruses (DENV-1 to -4). To estimate DENV seroincidence in school-aged children, a 1-year prospective cohort study was conducted in Patillas, Puerto Rico; 10- to 18-year-olds (N = 345) were randomly selected from 13 public schools. At enrollment, 49.8% of the entire cohort had DENV immunoglobulin G (IgG) anti-DENV antibodies, and there were individuals with neutralizing antibodies specific to each of the four DENV. The mean age of participants with incident DENV infection was 13.4 years. The 1-year seroincidence rate was 5.6%, and 61.1% of infections were inapparent. Having IgG anti-DENV at enrollment was associated with seroincidence (risk ratio = 6.8). Acute febrile illnesses during the study period were captured by a fever diary and an enhanced and passive surveillance system in the municipios of Patillas and Guayama. In summary, at enrollment, nearly one-half of the participants had a prior DENV infection, with the highest incidence in the 10- to 11-year-olds, of which most were inapparent infections, and symptomatic infections were considered mild.

Laboratory diagnosis and incidence of Dengue virus infection: a hospital based study, Perambalur

Background: Tamil Nadu recorded more than one fourth of all dengue cases and deaths in the country the state recorded 9,249 dengue cases and 60 deaths in 2012. There is a need for specific, inexpensive dengue diagnostic tests that can be used for clinical management, surveillance and outbreak investigations and would permit early intervention to treat patients and prevent or control epidemics. Material and methods: This cross sectional study was done by using MAC capture ELISA for IgM, IgG capture ELISA and NS1 antigen detection by sandwich ELISA during 2013 to 2014 for one year. Results: Out of 151 suspected cases of dengue 60 were found to positive by using dengue ELISA kit. The incidence of dengue viral infection was 39.74%, whereas during 2012 to 2013 out of 162 samples 27 (incidence 16.66%) were positive in our hospital based on statistics as mentioned above. Conclusion: The laboratory diagnosis of dengue virus infection by three ELISA methods along with clinical correlation with proper case definition had improved case detection as well as proper treatment in our hospital. Based on this study we can conclude that September, October, November, and December are the months of higher incidence of dengue virus infection.

The Nicaraguan Pediatric Dengue Cohort Study: Incidence of Inapparent and Symptomatic Dengue Virus Infections, 2004–2010

Dengue, caused by the four serotypes of dengue virus (DENV), is the most prevalent mosquito-borne viral disease of humans. To examine the incidence and transmission of dengue, the authors performed a prospective community-based cohort study in 5,545 children aged 2–14 years in Managua, Nicaragua, between 2004 and 2010. Children were provided with medical care through study physicians who systematically recorded medical consult data, and yearly blood samples were collected to evaluate DENV infection incidence. The incidence of dengue cases observed was 16.1 cases (range 3.4–43.5) per 1,000 person-years (95% CI: 14.5, 17.8), and a pattern of high dengue case incidence every other year was observed. The incidence of DENV infections was 90.2 infections (range 45.2–105.3) per 1,000 person-years (95% CI: 86.1, 94.5). The majority of DENV infections in young children (<6 years old) were primary (60%) and the majority of infections in older children (≥9 years of age) were secondary (82%), as expected. The incidence rate of second DENV infections (121.3 per 1,000 person-years; 95% CI: 102.7, 143.4) was significantly higher than the incidence rate of primary DENV infections (78.8 per 1,000 person-years; 95% CI: 73.2, 84.9). The rigorous analytic methodology used in this study, including incidence reporting in person-years, allows comparison across studies and across different infectious diseases. This study provides important information for understanding dengue epidemiology and informing dengue vaccine policy.

Epidemiological trends and clinical manifestations of Dengue among children in one of the English-speaking Caribbean countries

The epidemiology and clinical presentation of dengue fever among children in the Caribbean is poorly characterized. We therefore studied the epidemiology, clinical presentation, immunological characteristics, morbidity and mortality from dengue virus infection among children in Barbados, one of the English-speaking Caribbean countries. In this population-based, retrospective descriptive study, we screened all children on the island up to the age of 16 years who presented over a 10-year period (January 2000 through December 2009) with febrile illness and suspected dengue virus infection (n = 1809). We report on all the laboratory-confirmed cases of dengue (702/1809), for 545 of which we had complete clinical data. The annual incidence of dengue virus infection among children ranged between 0.29 and 2.92 cases/1000 children, with most cases seen during October through January. Children presented with undifferentiated fever (287/545, 53%), classical dengue fever (225/545, 41%), dengue hemorrhagic fever (15/545, 3%) and expanded dengue syndrome (i.e. severe involvement of liver, kidneys, brain, heart, or other unusual manifestations) (18/545, 3%). In most cases (73%), the infection was secondary. Thirty per cent of cases were diagnosed among hospitalized children and the overall crude mortality rate was 0.3%. Our study for the first time describes the epidemiology and disease characterization of dengue in Barbados, and quantifies the morbidity and mortality among children for this rapidly emerging public health problem in the Caribbean sub-region of the Americas.

Risk factors for the incidence of dengue virus infection in preschool children

To estimate the seroincidence of dengue in children living in Salvador, Bahia, Brazil and to evaluate the factors associated. A prospective serological survey was carried out in a sample of children 0-3 years of age. A multilevel logistic model was used to identify the determinants of seroincidence. The seroprevalence of dengue was 26.6% in the 625 children evaluated. A second survey detected an incidence of 33.2%. Multilevel logistic regression showed a statistically significant association between the seroincidence of dengue and age and the premises index. In Salvador, the dengue virus is in active circulation during early childhood; consequently, children have heterotypic antibodies and run a high risk of developing dengue haemorrhagic fever, because the sequence and intensity of the three dengue virus serotypes currently circulating in this city are very similar to those that were circulating in Rio de Janeiro, Brazil, in 2008. Therefore, the authors strongly recommend that the health authorities in cities with a similar epidemiological scenario be aware of this risk and implement improvements in health care, particularly targeting the paediatric age groups. In addition, information should be provided to the population and actions should be implemented to combat this vector.

Incidence of dengue virus infection among Japanese travellers, 2006 to 2010

Dengue continues to be a global public health concern. In Japan, although dengue cases are currently seen only among travellers returning from endemic areas, the number of reported cases is rising according to the national case-based surveillance system. We evaluated the characteristics of dengue cases imported into Japan and the relationship between the incidence of infection and season of travel to popular destinations. Dengue cases reported to the national surveillance system were retrospectively examined. The number of reported cases per number of Japanese travellers to a dengue-endemic country was calculated to estimate the country-specific incidence of imported dengue virus infection. The incidence of dengue infection among Japanese travellers was compared between dengue high season and low season in each country using relative risk (RR) and associated 95% confidence intervals (CI). Among 540 Japanese residents who were reported as dengue cases from 2006 to 2010, the majority had travelled to Indonesia, India, the Philippines and Thailand. The RR of dengue infection among Japanese travellers during dengue high season versus low season was 4.92 (95% CI: 3.01-8.04) for the Philippines, 2.76 (95% CI: 1.67-4.54) for Thailand and 0.37 (95% CI: 0.15-0.92) for Indonesia. Overall, higher incidence of imported cases appeared to be related to historic dengue high seasons. Travellers planning to visit dengue-endemic countries should be aware of historic dengue seasonality and the current dengue situation.

Cases of travel-acquired dengue fever in Denmark 2001–2009

Dengue fever (DF) remains one of the most important emerging infectious diseases. Whereas DF is well recognized in endemic countries, there are indications that the disease is underdiagnosed among travellers to endemic regions. Here, we present the first descriptive survey on cases of travel-acquired DF imported to Denmark diagnosed at the national reference laboratory for dengue virus diagnostics during a 9-year period. In our study, 16 – 46 travel-acquired dengue virus infections were diagnosed per year. DF is mainly imported by adults, mostly men, returning from Southeast Asian countries. The minimum incidence of dengue virus infection among Danish travellers is estimated to be 4.9 per 100 000 travellers. Our results confirm and expand studies from other European countries, and underline the importance of surveillance based on relevant diagnostic analyses.

The seroprevalence and seroincidence of dengue virus infection in western Kenya

Epidemics of dengue fever have been documented throughout the African continent over the past several decades, however little is known about the prevalence or incidence of dengue virus infection in the absence of an outbreak. No studies have analyzed the prevalence of dengue infection in western Kenya to date. This study describes the seroincidence and seroprevalence of dengue infection in western Kenya. Banked sera obtained from 354 healthy, afebrile children ages 12-47 months from Kisumu District, Kenya, were analyzed for antibodies to dengue virus using an IgG indirect ELISA. We found a seroprevalence of 1.1% (4 of 354 samples) and incidence of 8.5 seroconversions per 1000 persons per year in this study population. This appears to be similar to that previously reported in coastal regions of the country outside of known epidemic periods. Since there has never been a reported dengue epidemic in western Kenya, continued investigation and evaluation in a patient population presenting with fever is necessary to further confirm this finding.

Change in Age Pattern of Persons with Dengue, Northeastern Brazil

To the Editor: Approximately 40% of the world’s population is at risk for dengue (1). Epidemiologic characteristics of dengue differ by region, and disease incidence varies by patient age. In Southeast Asia, incidence of dengue fever (DF) and dengue hemorrhagic fever (DHF) is highest among children (2,3); in the Western Hemisphere, incidence of these diseases is higher among adults. In Brazil, which has ≈80% of dengue cases in the Western Hemisphere, adults are at risk for dengue virus (DENV) infection (3,4). However, in 2007, a total of 53% of persons in Brazil hospitalized with DHF were children <15 years of age; this proportion was highest (65.4%) in children in northeastern Brazil (5). In Ceara, a state in northeastern Brazil, DENV-1 epidemics have occurred since 1987. DHF cases have been reported since 1994 when DENV-2 was identified. In 2003, a severe DENV-3 epidemic occurred, and DHF incidence was high among adults (6). However, since 2007, incidence of DENV infection has been highest among children (7). To better understand factors that could affect this change in risk by age group, we studied the temporal progression of age distribution of persons with dengue during 1998–2008 in Ceara. We used data for Ceara from the National System of Notifiable Diseases (DF and DHF cases), the Hospital Admission Data System (dengue hospitalizations) (8), and the Central Public Health Laboratory (virus isolation). For each age group ( 60 years), we calculated incidence of DF and hospitalization rate for DHF. We also calculated proportions of dengue serotypes per year (2001–2008). Medians for continuous variables were compared by using the Kruskal-Wallis test. Analyses were performed by using Epi Info version 6.0 software (Centers for Disease Control and Prevention, Atlanta, GA, USA). From 1998 (10.8 cases/100,000 persons) through 2007 (236.7 cases/100,000 persons), DF incidence was lowest among persons 60 years of age (305.6, 331.5, and 249.9 cases/100,000 persons, respectively). Since 2007, the incidence of DHF among children was already higher (4,884 cases/100,000 persons) than among the other age groups (3,261, 3,387 and 2,789 cases/100,000 persons, respectively). In 2008, incidence of DHF among children was 8,992 cases/100,000 persons, which was 2× that among persons 10–19 and 20–59 years of age and >3× that among persons >60 years of age. Median age of persons with DHF decreased from 38 years in 2001 to 18 years in 2008 (p<0.0001). Children <10 years age, who in 2001 accounted for 5% of all cases, accounted for 33% of cases in 2008. The hospitalization rate for dengue among children in Ceara followed a pattern similar to that for DHF and increased for children 40% of isolations. At this time, DENV-2 and DENV-1 represented 7.4% and 48.5% of isolations, respectively. DENV-3 then predominated in Ceara until 2006 when DENV-2 reemerged (1.4%). DENV-2 became the predominant serotype in 2007 (84%) and 2008 (76.1%) (Table). The increase in DHF incidence among children in Ceara during 2007–2008 was greater than the overall increase in Brazil (4,5). Because the predominant serotype in Ceara in 2007–2008 was DENV-2, two hypotheses may explain this phenomenon. First, a more virulent DENV-2 may have been introduced. Genetic sequencing of DENV-2 circulating in another state in Brazil during the 2008 epidemic, compared with the 1990 and 1998 epidemics, showed that all isolates had the same genotype (American/Asiatic); only a 2% had a phylogenetic change (9). Such a small difference cannot explain this change in the age group affected by dengue. Second, the time when 3 serotypes circulated in Ceara may not have favored development of antibodies against DENV-3 in children <10 years of age, although they were susceptible to DENV-2. DENV-1 and DENV-2 were circulating in Ceara before 2002 and caused DF epidemics and a few DHF cases. However, these diseases occurred predominantly in adults. Conversely, children had little likelihood of being infected with DENV-2 because the incidence of dengue before 2002 was low and the 2000 birth cohort had little contact with DENV-2, which was no longer circulating. Thus, most persons susceptible to DENV-2 were children. DENV-3 was circulating during 2003–2006 and affected persons of all ages. Thus, when DENV-2 reemerged in 2006, many adults in Ceara already had antibodies against it. However, children had no antibodies against DENV-2, although some had antibodies against DENV-3. This immunologic difference may have caused the higher incidence of dengue among children in Ceara during 2007–2008, particularly in view of severity of the 2 epidemics, increased risk for DHF (10), and number of hospitalizations for dengue during this period. Table Confirmed cases of dengue fever and dengue hemorrhagic fever, Ceara, Brazil, 1998–2008*