The demographic characteristics of pandemic influenza decedents among middle and low-income tropical countries are poorly understood. We explored the demographics of persons who died with influenza A (H1N1)pdm09 infection during 2009–2010, in seven countries in the American tropics.
We used hospital-based surveillance to identify laboratory-confirmed influenza deaths in Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, Panama and Dominican Republic. An influenza death was defined as a person who died within two weeks of a severe acute respiratory infection (SARI) defined as sudden onset of fever >38 °C, cough or sore-throat, and shortness of breath, or difficulty breathing requiring hospitalization, and who tested positive for influenza A (H1N1)pdm09 virus by real time polymerase chain reaction. We abstracted the demographic and clinical characteristics of the deceased from their medical records.
During May 2009-June 2010, we identified 183 influenza deaths. Their median age was 32 years (IQR 18–46 years). One-hundred and one (55 %) were female of which 20 (20 %) were pregnant and 7 (7 %) were in postpartum. One-hundred and twelve decedents (61 %) had pre-existing medical conditions, (15 % had obesity, 13 % diabetes, 11 % asthma, 8 % metabolic disorders, 5 % chronic obstructive pulmonary disease, and 10 % neurological disorders). 65 % received oseltamivir but only 5 % received it within 48 h of symptoms onset.
The pandemic killed young adults, pregnant women and those with pre-existing medical conditions. Most sought care too late to fully benefit from oseltamivir. We recommend countries review antiviral treatment policies for people at high risk of developing complications.
The online version of this article (doi:10.1186/s12889-015-2064-z) contains supplementary material, which is available to authorized users.
Early in the pandemic, the epidemiologic and clinical characteristics of influenza A (H1N1)pdm09 were poorly understood. Pending information about this emerging pathogen, influenza prevention and control policies in the American tropics still targeted persons at risk of developing complications as a result of seasonal influenza disease (e.g. children aged < 5 years, persons with certain chronic medical conditions, and persons aged ≥ 65 years) [
At the start of the pandemic, Central American countries used CDC’s Guidelines for Treatment of Suspected Cases of Influenza A(H1N1)pdm09 [
WHO also recommended to the countries vaccinate pregnant women and other high risk persons against pandemic influenza [
Pharmaceutical interventions in middle and low income countries of the American tropics were in limited supplies or only available late during the pandemic. In Central America, while in some countries social security coverage is almost universal, in others is as low as 12 %. Investment in health varies between 5-11 % of gross domestic product, the density of beds varies 0.7-2.4 per 1000 inhabitants; physician density 0.4-1.9 per 1000 inhabitants; and rural population of 25–50 % [
In 2007, the Ministries of Health of Central America and the Dominican Republic implemented the PAHO-CDC Generic Protocol for Influenza Surveillance to identify influenza among severe acute respiratory infection (SARI) cases (defined as sudden onset fever >38 °C, cough or sore-throat, and shortness of breath or difficulty breathing requiring hospitalization) [
We defined women of reproductive age as those aged between 15–49 years. We categorized pregnant women who developed respiratory illness before delivery as “pregnant” and those who developed respiratory illness within 42 days of delivery as “postpartum” cases. We categorized a case as obese if such a diagnosis was recorded in their medical record or if height and weight information were available and the body mass index exceeded 30 kg/m2.
We collected data using standardized questionnaires, from May 2009 to June 2010. Health authorities systematically obtained demographic (e.g. age and sex) and clinical information (e.g. date of illness onset, health seeking behavior, treatment with oseltamivir, history of pre-existing medical conditions, symptoms, signs, laboratory, radiology, and pathology findings) from SARI decedents associated with influenza A(H1N1)pdm09 from clinical records (by reviewing the medical records of hospitals, outpatient clinic records and referral sheets which were available) and obtaining information from relatives, and surveillance data.
The review of the clinical records was performed in the context of the pandemic outbreak for the characterization of the first 100 cases, following recommendations of WHO. For the emergency, at that moment, was no required approval for IRB. Approvals by Ministries of Health consisted of administrative permission to access medical records. The review of medical records was performed and with the accompaniment of officials of the Ministries of Health. No patient identifiers were received or used for analysis.
We summarized demographic and clinical characteristics of decedents associated with influenza A(H1N1)pdm09 using proportions to compare both, as the participation of each country and as the age groups, with variables of interest (ie. Percentage of pregnant and postpartum women, underlying medical conditions and treatment). We stratified the analyses into three age groups (i.e. 0–18, 19–64 and ≥65 years). We conducted Chi-square, t-tests and analysis of variance tests for comparisons when appropriate. We eliminated missing data from the calculations, buy declared in the results section.
We verify the check list for observational studies from the STROBE Statement.
During epidemiological week (EW) 19 in 2009 through EW 25 in 2010, we identified 183 SARI decedents who tested positive for influenza A(H1N1)pdm09 in seven countries (Belize did not identify any influenza A(H1N1)pdm09 deaths). The first case was identified in Costa Rica during EW 19. Influenza A(H1N1)pdm09 deaths peaked during EW 30 (Fig. Number decedents associated with influenza A(H1N1)pdm09 by epidemiological Week, in Central America, 2009-2010 Demographic characteristics of decedents associated with influenza A(H1N1)pnd09 in Central America, 2009-2010 The World Bank. Indicators. Birth rate, crude. Data section. Web page. Available in: Country Decedents for influenza H1N1pnd09 General population (2009) Number of cases Median age in years (IQR) Pregnant and postpartum women cases (%) Percentage of pregnant woman in the general population by countrya
Total country population (per million inhabitants)b
Costa Rica 74 41 (26–55) 4 (5 %) 1.6 % 4.6 Dominican Republic 21 25 (20–36) 5 (24 %) 2.2 % 9.8 El Salvador 32 15 (1–39) 6 (19 %) 2.1 % 6.1 Guatemala 17 34 (24–38) 5 (29 %) 3.3 % 14.0 Honduras 18 26 (3–42) 5 (28 %) 2.7 % 7.4 Nicaragua 9 30 (2–44) 1 (11 %) 2.4 % 5.7 Panama 12 23 (2–51) 1 (8 %) 2.1 % 3.5 All 183 32 (17–46) 27 (15 %) 2.3 % 51.1
The median age among cases was 32 years (interquartile range: 18–46 years). Children aged <5 years represented 16 % (29 cases) and persons aged 15–44 years represented 48 % (88 cases) and persons aged >65 years represented 9 % (17 cases) of the 183 deaths. El Salvador had the lowest median age (15 years) and Costa Rica the highest (41 years) among decedents (Table
Seventeen (9 %) of 183 cases had a history of smoking. Among 112 cases (61 %) with a pre-existing medical condition, 27 (15 %) were obese, 23 (13 %) had diabetes, 20 (11 %) had asthma, 15 (8 %) had other chronic metabolic diseases, 10 (5 %) had chronic obstructive pulmonary disease, 11 (6 %) had seizure disorder, and 7 (4 %) had cerebral palsy. Underlying medical conditions were identified in 38 % of cases <5 years old, in 61 % of cases aged 5–59 years old, and in all cases with 60 or more years old (Table Decedents associated with influenza H1N1pnd09. Pre-existing medical conditions in age risk groups and pregnant and postpartum women. Central America and Dominican Republic 2009–10 Percentages from the total of each categoryUnderlying medical condition All <5 years 5 - 59 years 60+ years Pregnant or postpartum
Cases % Cases % Cases % Cases % Cases % Obesity 27 15 % 0 0 % 23 17 % 4 21 % 2 7 % Diabetes Mellitus 23 13 % 0 0 % 16 12 % 7 37 % 2 7 % Asthma 20 11 % 2 7 % 15 11 % 3 16 % 5 18 % Other chronic metabolic disease 15 8 % 1 3 % 9 7 % 5 26 % 0 0 % Immunosuppression 15 8 % 2 7 % 10 7 % 3 16 % 1 4 % Chronic lung disease 10 5 % 0 0 % 8 6 % 2 11 % 2 7 % Chronic seizures 11 6 % 3 10 % 8 6 % 0 0 % 0 0 % Chronic cardiac disease 7 4 % 1 3 % 5 4 % 1 5 % 3 11 % Cerebral palsy 7 4 % 1 3 % 6 4 % 0 0 % 0 0 % At least one chronic condition 112 61 % 11 38 % 82 61 % 19 100 % 14 50 %
One hundred and one (55 %) of 183 the decedents were female. Of the 101 female decedents, 61 (60 %) were women of reproductive age. Thirty-three percent (20 cases) of women of reproductive age who died were pregnant, and 7 (12 %) were in their puerperium. El Salvador reported that all women of reproductive age who died were maternal deaths, Guatemala reported 5 (71 %) of 7, and Honduras reported 5 (63 %) of 8 were maternal deaths.
Nearly half (48 %) of the pregnant women were in their third trimester, 24 % in the second trimester, and 24 % did not have a gestational age recorded. Fourteen (52 %) of 27 maternal deaths had other underlying medical condition (i.e. 5 (18 %) had asthma, 3 (11 %) had cardiac disease, 2 [7 %] had obesity, 2 [7 %] had chronic lung disease, 2 [7 %] had diabetes and 1 [4 %] AIDS) (Table
One hundred and fifty-one (82 %) of 183 decedents had a history of fever before their first contact with a clinic, but only 85 (46 %) had documented fever during admission. Dyspnea was reported in only 124 (68 %) of cases during admission.
Seventy five (41 %) of 183 cases had a chest x-rays (CXR) during their illness, of which 71 % had consolidation 53 % had interstitial findings. Five (28 %) of the 18 cases with interstitial infiltrates subsequently developed consolidation during hospitalization. Sixteen (9 %) of the 183 cases had autopsy reports, of which 11 (69 %) had cardiomegaly, 5 (31 %) intra-alveolar hemorrhage, 4 (25 %) neutrophilic bronchopneumonia, and 4 (25 %) cerebral edema.
Decedents sought care a median of 4 days (IQR 1–5 days) after symptom onset. The median duration between health seeking and death was 14 days (IQR 6–17 days). There was no statistically significant difference in the average amount of time elapsed between symptom onset and health seeking by age groups ( Treatment of influenza A (H1N1)pnd09 in severe acute respiratory case-patients prior to death in Central America 2009-2010
aPercentage of total category. bPercentage who received oseltamivirTreatment All Age groups Pregnancy or postpartum <5 years 5–59 years +60 years Cases % Cases % Cases % Cases % Cases % Acute respiratory distress syndromea
134 73 20 69 97 73 17 81 17 63 Intensive care admissiona
113 62 18 62 84 63 11 52 15 56 Mechanical ventilationa
134 73 21 72 96 72 17 81 15 56 Oseltamivir 119 65 13 45 93 70 13 62 20 74 In first 48 h of symptoms onsetb
10 5 1 8 8 6 1 8 0 0 In first 72 h of symptoms onsetb
21 11 3 23 17 13 1 8 2 7
Fifty five percent (100/183 cases) were also tested through immunofluorescence for other respiratory virus. Two cases also were positive for respiratory syncytial virus, 1 for influenza B, 1 for adenovirus, 1 for parainfluenza virus. Twenty-three percent (43 cases) were tested for bacteremia through blood cultures; 1 was positive for
Decedents infected with influenza A(H1N1)pdm09 were frequently young, pregnant, or had other pre-existing medical conditions. Unlike seasonal influenza deaths, which predominately occur among older adults [
Such findings suggest that the influenza pandemic disproportionately affected pregnant women and mothers during their puerperium and consider targeting this group during future epidemic/pandemic periods with risk communications, early antiviral treatment, and vaccination [
Costa Rica had the higher proportion of deaths (40 %); this could be explained by diagnosis skills and access to health services in this country.
Although most influenza A(H1N1)pdm09 case-patients were treated with oseltamivir (65 %), less than 6 % received oseltamivir within 48 h of symptom onset when the antiviral are thought to be most effective [
This study has important limitations. We assumed that all SARI decedents identified by health authorities comprised the majority of laboratory-confirmed influenza A(H1N1)pdm09 deaths. It is likely that a proportion of persons with severe influenza A(H1N1)pdm09 illness may have remained unidentified or untested and that these persons could have had different demographic and clinical characteristics than those identified through surveillance. For example, it is possible that cases with pre-existing medical conditions may have been preferentially tested for influenza A(H1N1)pdm09 thus increasing the proportion of high risk laboratory-confirmed case-patients identified in our case-series. Also we have no access to socioeconomic status of cases.
Our study demonstrates the utility of influenza surveillance which provided valuable data to the epidemiology of influenza A(H1N1)pdm09 during 2009–2010. Our findings suggest that decedents associated with influenza A(H1N1)pdm09 were frequently young persons with prevalent pre-existing medical conditions. Our data suggest that few cases received oseltamivir within 48 h of treatment, highlighting challenges with the use of antivirals during periods of epidemic activity in the region. Based on these data, current national treatment protocols urge clinicians prioritize individuals with preexisting medical conditions such as pregnancy, asthma, and diabetes for timely oseltamivir treatment. Future studies should explore the availability and accessibility of oseltamivir as well as the potential value for presumptive treatment of high-risk individuals during periods of epidemic influenza activity in tropical middle and low income countries.
Acquired immune deficiency syndrome
Centers for Disease Control and Prevention
Chest X Rays
Epidemiological week
Corresponding to pandemic strain of influenza for 2009
Interquartile range
Odds ratio
Pan American Health Organization
Severe acute respiratory infection
World Health Organization
The authors declare that they have no competing interests.
RC has designed the research, has participate in acquisition of data; He has been performed the analysis and interpretation of data; and have been involved in drafting the manuscript. SM participated in the analysis of data, and helped to draft the manuscript. DR participated in the data acquisition from El Salvador, and helped to draft the manuscript. AP participated in the data acquisition from Guatemala, and helped to draft the manuscript. GG participated in the data acquisition from Costa Rica, participated in recovery of background and design and to draft the manuscript. LM participated in the data acquisition from Panama. CT participated in the data acquisition from Dominican Republic. JJ helped to draft the manuscript. NB helped to draft the manuscript. LB participated in the design and helped to draft the manuscript. WC has advised all steps of the study, included design, interpretation of data and drafting the manuscript. PM participated in the design of the study. RP helped to draft the manuscript. EA has advised on data interpretation, design of the manuscript and helped to draft the manuscript. All authors have read and approved the final manuscript.
Dr. Nivaldo Linares Former Coordinator of CDC-CAR Influenza Program. Staff of the laboratory influenza of Ministry of Health of Central America and Dominican Republic: Celina Calderon (El Salvador), Leticia Castillo (Guatemala), Jenny Lara (Costa Rica), Alex Martinez (Panama) and Mildred Disla (Dominican Republic); the Informatics team of the Influenza Program including Marcelo Adaglio and Daniel Otzoy; and the CDC Influenza Division including Nancy Cox, Joseph Bresee, Ann Moen and Marc-Alain Widdowson.
The opinions expressed by authors contributing to this journal do not necessarily reflect the opinions of the Centers for Disease Control and Prevention or the institutions with which the authors are affiliated.
This study was supported by the Cooperative Agreement No. 1U01GH000028-03 from the U.S. Centers for Disease Control and Prevention. None of the coauthors have any conflicts of interest to declare. The findings and conclusions in this report are those of the authors and do not necessarily reflect the official position of the Centers for Disease Control and Prevention or the institutions with which the authors are affiliated.