Clusters of Hantavirus Infection, Southern Argentina

An important known risk factor for person-to-person transmission of ANDV is prolonged or close contact with symptomatic persons.

“An important known risk factor for person-to-person transmission of ANDV is prolonged or close contact with symptomatic persons.17,18,21”

The measures reduced the number of potential case contacts, which may have allowed high-risk household contacts to be attended and treated and may have resulted in earlier detection of infection.

“In addition, these measures reduced the number of potential case contacts, which may have allowed high-risk household contacts to be attended to and treated and may have resulted in detection of infection in the earlier stages of progression of hantavirus pulmonary syndrome.18”

When all case-patients remain in the disease endemic area, molecular dissimilarities rule out person-to-person transmission, but identical sequences do not support it.

““When all case-patients remain in the disease endemic area … molecular dissimilarities rule out person-to-person transmission, but identical sequences do not support it” [10].”

The use of genetic sequencing data to confirm human-to-human transmission has the limitation of only providing strong evidence when cases that occur in different geographic areas have identical sequences.

“While the use of genetic sequencing data to confirm human-to-human transmission has been used in investigations of clusters in Argentina and Chile [7–11, 25, 26, 32, 35], it has the limitation of only providing strong evidence when cases that occur in different geographic areas have identical sequences.”

Human-to-human transmission of the Andes virus (ANDV) has been claimed to occur in Argentina and Chile, beginning with the 1996 outbreak in southern Argentina.

“Human-to-human transmission of the Andes virus (ANDV) was first claimed to have occurred as part of the 1996 outbreak in southern Argentina [6–8], and since then a number of studies have reported more cases and suggested the involvement of this form of transmission in both Argentina and Chile [9–11].”

Of the 14 noncomparative studies, 7 were conducted in Argentina (6 analyses of clusters and 1 seroprevalence study) and 3 in Chile (2 analyses of clusters and 1 seroprevalence study).

“Of the 14 noncomparative studies, 7 were conducted in Argentina (6 analyses of clusters and 1 seroprevalence study) [8–10, 13, 25, 26, 32] and 3 in Chile (2 analyses of clusters and 1 seroprevalence study) [11, 14, 35] (Supplementary Table 2).”

In Argentina, all but 1 of the studies showed some evidence of human-to-human transmission in investigations of clusters, with up to 16 likely cases reported between 1996 and 2014.

“In Argentina, all but 1 of the studies showed some evidence of human-to-human transmission in investigations of clusters [8–10, 25, 26, 32], with up to 16 likely cases of human-to-human transmission reported between 1996 and 2014.”

Co-exposure to rodents cannot be ruled out as an explanation for the cases.

“co-exposure to rodents cannot be ruled out.”

For the noncomparative studies, the evidence for human-to-human transmission is limited to analyses of clusters in Chile and Argentina, and these findings are not supported by seroprevalence studies conducted in these countries after hantavirus outbreaks in the population.

“For the noncomparative studies, the evidence for human-to-human transmission is limited to analyses of clusters in Chile [11, 35] and Argentina [8–10, 26, 32] and these findings are not supported by seroprevalence studies conducted in these countries after hantavirus outbreaks in the population [13, 14].”

The identical ANDV sequences between cases can also be explained by exposure to the same viral variant within the local rodent populations.

“the identical sequences can also be explained by exposure to the same viral variant within the local rodent populations [10, 32] (most of the cases lived in the same town)”