In the absence of PNU112455A influenza virologic surveillance, sentinel surveillance for ILI may more accurately monitor influenza activity than Google Flu Trends Cardionogen-2 during anomalous influenza seasons. Furthermore, given the non-specific nature of ILI, robust nationwide virologic surveillance remains critical to the understanding of influenza activity during inter-pandemic and pandemic periods alike. HIV requires host cell coreceptors such as CCR5 and/or CXCR4 in addition to CD4 for cell-entry. Viruses that use CCR5-molecules for cellular entry are referred to as ����R5.���� Viruses that use receptors other than CCR5, including the CXCR4-using ����X4���� viruses and the ����dual/mixed-tropic���� populations can collectively be termed ����non-R5.���� As CCR5-antagonists are only effective against R5 virus, viral tropism must be determined before prescribing this drug class. At the time of publication, maraviroc remains the first and only CCR5- anatognist approved for clinical use. There are two approaches to determine plasma viral tropism commonly used in North America, phenotypic and genotypic. The phenotypic method offered by Monogram Biosciences in the United States, the Enhanced Sensitivity Trofile Assay utilizes env gene cloning and an infection-based assay. Genotypic methods are based on the amplification and population- sequencing of the V3-loop from patient viruses; ����deep���� sequencing technologies such as 454 offers sensitivity comparable to phenotypic assays and outperforms populationsequencing in the detection of viral quasispecies for HIV tropism prediction and have recently gained popularity. The V3-loop sequences are interpreted using prediction algorithms such as geno2pheno. However, both phenotypic and genotypic tropism prediction methods are limited to testing samples with sufficient plasma viral load typically above 250 HIV RNA copies/mL. The majority of patients initiating highly active antiretroviral therapy successfully suppress plasma viral load to undetectable levels, making it impossible to perform viral tropism testing during viral suppression due to the detection limits of these plasma-based assays.