Comparing Deaths from Influenza H1N1 and Seasonal Influenza A: Main Sociodemographic and Clinical Differences between the Most Prevalent 2009 Viruses

Abstract

Background. During the 2009 spring epidemic outbreak in Mexico, an important research and policy question faced was related to the differences in clinical profile and population characteristics of those affected by the new H1N1 virus compared with the seasonal virus. Methods and Findings. Data from clinical files from all influenza A deaths in Mexico between April 10 and July 13, 2009 were analyzed to describe differences in clinical and socioeconomic profile between H1N1 and non-H1N1 cases. A total of 324 influenza A mortality cases were studied of which 239 presented rt-PCR confirmation for H1N1 virus and 85 for seasonal influenza A. From the differences of means and multivariate logistic regression, it was found that H1N1 deaths occurred in younger and less educated people, and among those who engage in activities where there is increased contact with other unknown persons (OR 4.52, 95% CI 1.56–13.14). Clinical symptoms were similar except for dyspnea, headache, and chest pain that were less frequently found among H1N1 cases. Conclusions. Findings suggest that age, education, and occupation are factors that may be useful to identify risk for H1N1 among influenza cases, and also that patients with early dyspnea, headache, and chest pain are more likely to be non-H1N1 cases.

Demographic and Spatiotemporal Patterns of Avian Influenza Infection at the Continental Scale, and in Relation to Annual Life Cycle of a Migratory Host

“…The positive association between AIV infection and latitude was not linear, with no additional increased risk in AIV infection beyond ~43° north, beyond which there was a plateau and slightly declining trend. Although colder temperatures are generally better for virus survival, it has been demonstrated experimentally that extremely cold temperatures (below -30°C) may decrease virus survival in the environment [ 39 ], which may explain this non-linear trend. In addition, latitudinal patterns were most prominent in July-August and during fall migration, particularly in HY birds, thus the latitudinal trend may have been driven in part by the interaction between age and host annual life cycle (season) and associated with changes in host density and increases in immunity as birds disperse among wintering areas southward.…”

The association between socioeconomic status and pandemic influenza: systematic review and meta-analysis

“…Most of the studies used data from North America, including 11 for USA (17, 27, 30, 33, 40, 41, 48, 50, 55, 56, 59) and 6 for Canada (38, 45, 49, 52, 60, 62); Europe, including 6 for England (16, 26, 31, 32, 44, 64), 4 for Spain (39, 46, 51, 57), 2 for Norway (13, 14), and 1 for 30 EU/EFTA countries (53); 4 for Australia (42, 43, 54, 61) and 3 for New Zealand (28, 29, 34). While a few studies used data from Central America/South America including 1 for Mexico (37) and 1 for Brazil (47), and Asia, including 1 for Iran (35) and 1 for China (63), we identified no studies using data from Africa. Finally, 3 studies had a global approach studying several countries (15, 36, 58).…”

“…Studies using only ecological SES variables thus picked up a combination of individual-level and area-level SES effects on the outcome variables. Finally, in 17 of the studies, outcomes, explanatory variables and controls are all measured for individuals and the data aggregation level was thus the individual level (14, 28, 29, 34, 35, 37-40, 45-48, 51, 57, 60, 63).…”

“…The 3 broad categories of outcomes were studied (see details in Table 1): 1) people seeing doctors due to symptoms of influenza like illness (ILI)/influenza transmission(R0)/lab-confirmed influenza infection (using PCR tests)/immunity towards influenza (using blood serum samples to look for antibodies) (26, 27, 30, 32, 34, 35, 41-45, 52, 54, 57, 60, 61, 63); 2) lab-confirmed influenza hospitalizations/ICU treatment/mechanical ventilation (17, 33, 38, 39, 46-51, 55, 57, 59, 62); 3) lab-confirmed pandemic deaths/Influenza-Pneumonia (PI) deaths/excess deaths associated with pandemic influenza (13-16, 26-31, 36, 37, 40, 53, 56, 58, 59, 64).…”

Epidémiologie virale et sévérité clinique pendant le pic d’épidémie grippale A(H1N1) variant dans les atteintes respiratoires fébriles de l’enfant

“…Comme dans de nombreuses études, la symptomatologie de l'infection A(H1N1)v était peu spécifique avec une toux associée à une fièvre [4,19,20], des atteintes digestives fréquentes [21], pas de prédominance de sexe [19] et une prépondérance des surinfections pulmonaires parmi les complications [18]. La symptomatologie clinique est donc peu contributive pour identifier ces virus [1,22,23] et les anomalies paracliniques sont très peu spécifiques [4]. Un terrain à risque a été observé chez près de la moitié des enfants porteurs du virus A(H1N1)v, en concordance avec d'autres études (50 à 80 %) [4,24] mais sans prédominance de l'asthme habituellement présent.…”