White spot syndrome virus (WSSV) is the viral pathogen with the most negative impact on shrimp farming. In Sonora, Litopenaeus vannamei culture has decreased 50% during 2010-2012 due to WSSV outbreaks. The ORF94 has proven to be most useful for the analysis of WSSV variability. Several studies have suggested a correlation between its Repeat Units (RUs) and WSSV virulence as follows: the fewer RUs (<9) the higher mortality rate. In order to support this, we analyzed shrimps from eight farm periods and identified the WSSV-variety present in each one. In outbreaks, the presence of <8 RUs with a dominance of 3 RUs was notable in the last four years. Although it is still not clear how host-virus interactions and pond´s environment affect the transition of the infection just from the presence of the virus in shrimps to an outbreak, these results are a step forward in understanding the pond status and ways of predicting the likelihood of a WSSV infection becoming an outbreak.White spot syndrome virus (WSSV) is the viral pathogen with the most negatively impact on shrimp farming. In Sonora, Litopenaeus vannamei culture has decreased 50% during 2010-2012 due to WSSV outbreaks. The ORF94 has proven to be most useful for analysis of WSSV variability, several studies have suggested a correlation between its Repeat Units (RUs) and WSSV virulence as follows: the fewer RUs (