Influenza and other respiratory viruses in three Central American countries

Abstract

Background: Despite the disease burden imposed by respiratory diseases on children in Central America, there is a paucity of data describing the etiologic agents of the disease.

Aims: To analyze viral etiologic agents associated with influenza-like illness (ILI) in participants reporting to one outpatient health center, one pediatric hospital, and three general hospitals in El Salvador, Honduras, and Nicaragua Material &

Methods: Between August 2006 and April 2009, pharyngeal swabs were collected from outpatients and inpatients. Patient specimens were inoculated onto cultured cell monolayers, and viral antigens were detected by indirect and direct immunofluorescence staining.

Results: A total of 1,756 patients were enrolled, of whom 1,195 (68.3%) were under the age of 5; and 183 (10.4%) required hospitalization. One or more viral agents were identified in 434 (24.7%) cases, of which 17 (3.9%) were dual infections. The most common viruses isolated were influenza A virus (130; 7.4% of cases), respiratory syncytial virus (122; 6.9%), adenoviruses (63; 3.6%), parainfluenza viruses (57; 3.2%), influenza B virus (47; 2.7% of cases), and herpes simplex virus 1 (22; 1.3%). In addition, human metapneumovirus and enteroviruses (coxsackie and echovirus) were isolated from patient specimens.

Discussion: When compared to the rest of the population, viruses were isolated from a significantly higher percentage of patients age 5 or younger. The prevalence of influenza A virus or influenza B virus infections was similar between the younger and older age groups. RSV was the most commonly detected pathogen in infants age 5 and younger and was significantly associated with pneumonia (p < 0.0001) and hospitalization (p < 0.0001).

Conclusion: Genetic analysis of influenza isolates identified A (H3N2), A (H1N1), and B viruses. It also showed that the mutation H274Y conferring resistance to oseltamivir was first detected in Honduran influenza A/H1N1 strains at the beginning of 2008. These data demonstrate that a diverse range of respiratory pathogens are associated with ILI in Honduras, El Salvador, and Nicaragua. RSV infection in particular appears to be associated with severe disease in infants in the region.

Figure 1

Map of study sites in El Salvador, Honduras, and Nicaragua.

Figure 2

Neighbor‐joining phylogenetic analyses based on partial hemagglutinin gene sequence (approximately 1000 bp) of 33 H1N1 influenza A isolates from Nicaragua and Honduras with three distinct genotypes: 1) A/Solomon Islands/03/06‐like, 2) A/Brisbane/59/07‐like, and 3) A/New Caledonia/20/99‐like. Neighbor‐joining and maximum likelihood analyses yielded similar tree topology.

Figure 3

Neighbor‐joining phylogenetic analyses based on the hemagglutinin gene of 23 H3N2 influenza A isolates from Central America revealed three genotypes: 1) A/Brisbane/101/05‐like, 2) A/Honduras/AF1064/06‐like, and 3) A/Brisbane/10/07‐like. Neighbor‐joining and maximum likelihood analyses yielded similar tree topology.

Figure 4

Neighbor‐joining phylogenetic analyses based on the HA sequence of 23 influenza B isolates revealed the presence of two genotypes in Central America: B/Malaysia/2506/07‐like and B/Florida/4/06‐like. Neighbor‐joining and maximum likelihood analyses yielded similar tree topology.