During 2009, 626 patients died with laboratory-confirmed influenza A H1N1pdm infection in Argentina 
. The proportion of confirmed hospitalized case-patients who died peaked during June (i.e. 48 [18%] of 272) (). Of the 626 fatalities, 377 were reported during June 15-July 31 (the study period). Forty-five were excluded because 37 were not confirmed by RT-PCR and eight had incomplete medical charts.
Pandemic H1N1 (influenza A H1N1pdm) confirmed hospitalizations and deaths by week of symptom onset and case fatality proportion among hospitalized cases, Argentina, May 3rd 2009–August 29th 2009.
The remaining 332 fatalities had a median age of 36 years (IQR
13–53 years) and 177 (53%) were male. Children aged <18 years accounted for 93 (28%) of fatalities, those aged <5 years comprised 48 (52%), and infants aged less <6 months comprised 16 (33%). Although more fatalities were reported among patients aged 19–49 years, laboratory-confirmed influenza A H1N1pdm fatalities per 100,000 population were more common among children aged <5 years and persons aged 50–64 years ().
Age and sex distribution of fatalities reported from June 15th to July 31st 2009, Argentina.
Thirty fatalities were not hospitalized for influenza symptoms but rather acquired nosocomial influenza A H1N1pdm infections. Excluding these cases, the most common symptoms at admission were dyspnea (94%), cough (93%), and history of fever (85%). During admission, most patients had elevated respiration rates (73%) and heart rates (69%). On auscultation, crackles were more common among fatalities aged ≥5 years compared to fatalities <5 years (89% vs. 63%, p<0.01). Anemia was present in 54% of patients, and more common among those aged <5 years (67%, p<0.01) (). Of 134 fatalities with available data, 110 (82%) presented with lymphopenia. Of 159 fatalities with available data, 65 (41%) had thrombocytopenia. Elevated urea was more common among patients aged ≥50 compared to the other age groups (p<0.001). Eighty-two percent of patients had oxygen saturation <96%) which was more common among patients ≥5 years (p<0.01); while acidosis (pH<7.36) and elevated pCO2 (>44 mmHg) were more common among patients <5 years (p<0.01) ().
Table 2 Selected symptoms and physical signs at time of admission by age group in influenza A H1N1pdm confirmed fatalities (excluding patients with influenza A H1N1pdm nosocomial infections unless otherwise reported), Argentina, June 15th–July 31st, 2009. (more ...)
Selected hematology at time of admission by age group in influenza A H1N1pdm confirmed fatalities (excluding patients with influenza A H1N1pdm nosocomial infections unless otherwise reported), Argentina, June 15–July 31, 2009.
Among 176 patients with admission radiographs, (79%) had bilateral chest infiltrates, 71 (40%) had consolidation, 61 (35%) had interstitial pattern, 37 (21%) had both, and six (3%) had other findings (). For 236 (71%) of the 332 patients (including those with nosocomial infections), the primary hospital admission diagnosis was pneumonia. Pneumonia, however, only accounted for 54% of the primary diagnoses among children aged <5 years, with other respiratory illnesses accounting for over one third of the admission diagnosis among this age group.
Selected X-ray patterns at time of admission by age group in influenza A H1N1pdm confirmed fatalities (excluding patients with influenza A H1N1pdm nosocomial infections unless otherwise reported), Argentina, June 15th–July 31st, 2009.
Of 304 patients admitted for influenza A H1N1pdm-associated illness (excluding nosocomial infections), the median time from symptom onset to admission was five days (IQR, 3–7 days). Most patients (299 [95%] of 315) needed ICU admission and, 292 were mechanically ventilated for a median of six days (IQR, 2–12 days). Among the 252 patients with available information on the start date of their mechanical ventilation, 207 (82%) were mechanically ventilated within the first 24 hours of admission to intensive care ().
Treatment and Clinical course of 332 influenza A H1N1pdm-confirmed fatalities, June 15th–July 31st, 2009.
The most frequent organ failure was respiratory failure (97%). Additionally, 85% of the patients met the criteria for acute respiratory distress syndrome (ARDS) during their hospitalization. These patients had hypoxemia [median Pa/FiO2 87 (IQR: 60–129)], hypercapnia [median PaCO2 54 (IQR: 43–72), and acidosis [median pH 7.24 (IQR: 7.10–7.33) requiring elevated concentration of oxygen (FiO2 100% in 72% of cases), maximal high positive end expiratory pressure [median 15 (IQR: 10–18)] and use of ventilation in prone position or alveolar recruitment maneuvers in 41% of patients. Hemodynamic failure requiring vasoactive drugs occurred in 54% of patients. Renal failure was present in 134 (43%) of the 312 patients with available data and 29% of these required dialysis. Of the 134 patients with renal failure, 31 (23%) had previous chronic renal failure of which eight [6%] were on chronic hemodialysis. Six (13%) of 47 children aged <5 years with available data developed renal failure compared to 128 (48%) of 265 persons aged ≥5 years (p<0.0001).Hematologic failure was diagnosed in 44%, hepatic failure in 5% and multiorgan failure in 71% of influenza A H1N1pdm fatalities.
Of all 332 patients, 290 (87%) received antiviral treatment; 183 (76%) ≤2 days of admission but only 33 (13%) of 253 with information on timing of administration received antivirals ≤48 hours of symptom onset. None of the 48 fatalities aged <5 years received antivirals ≤48 hours of symptom onset; 20% of these children received antivirals ≤48 hours of a doctor's visit, and only 55% received antivirals ≤48 hours of hospitalization compared to at least 78% in older age groups ().
As the pandemic progressed, the mean time from symptom onset to first doctor visit and symptom onset to hospitalization among fatalities decreased (p<0.001). Similarly, the mean time from symptom onset to antiviral treatment decreased from 19 days during epidemiologic week 22 to four days during week 28 (p<0.001). The time from the first doctor visit to antiviral treatment also decreased as the pandemic progressed (p<0.001) while the time from hospitalization to antiviral treatment remained brief ().
Figure 2 Mean number of days from date of onset to date of first doctor visit (A), hospitalization (B), and antiviral treatment (C); Mean number of days from first doctor visit (D) and hospitalization (E) to antiviral treatment among influenza A H1N1pdm fatalities (more ...)
At least one comorbidity 
was reported in 75% of cases with such information in their charts. The most common comorbidities were chronic pulmonary disease (including asthma) in 28%, metabolic disorder (including diabetes) in 25%, and immunosuppression in 24% of fatalities. Among children aged <5 years, chronic pulmonary disease (42%) was also the most common comorbidity followed by neonatal pathologies (i.e. genetic disorders, congenital malformations, and preterm births) (35%) and neurologic disease (19%) (). The prevalence of asthma was low among fatalities (6%). In contrast, 4% of patients were HIV positive, a proportion higher than the 0.4% country prevalence 
. Similarly, 32% of fatalities were obese, a proportion higher than the 15% country prevalence 
Comorbidities* and underlying conditions among influenza A H1N1pdm confirmed fatalities by age groups, Argentina, June 15th–July 31st, 2009.
We identified 16 pregnant women and four postpartum women among fatalities. Four of the pregnant women were in their second trimester while 11 were in their third trimester. Eight delivered by caesarean section after being admitted to the ICU, two whom had stillbirths. Pregnant women had significantly longer ICU stays than non-pregnant women aged 15–44 years (11 vs. 4 days, p
0.01). One pregnant and two postpartum women did not receive any antiviral treatment during the course of their illness. Among the 17 pregnant or postpartum women that received antivirals, none received them within the recommended 48 hours after illness onset but a median of seven days (IQR: 5–9 days) later. Fifty percent received antivirals <1 day after hospitalization ().
Description of pregnant, postpartum and fertile age women among influenza A H1N1pdm confirmed deceased patients, Argentina, June 15th–July 31st, 2009.