Worldwide, infectious diseases cause 16% of deaths each year. It is evident that in the past many of the deadly diseases originated in countries with little to none or fewer resources to contain the spread of the disease. To combat such diseases, improvements in nucleic acid testing (NAT) to enable rapid and accurate detection of viruses in low resources settings are needed. Current NAT instruments are bulky, expensive, and slow, limiting the potential for point-of-care applications. Here we present a portable spectrometer based system capable of performing quantitative NAT utilizing isothermal polymerase chain reaction (PCR) variants. A micro spectrometer used in the device enables the detection of a continuous fluorescence spectrum allowing multiplex detection of different DNA labeling dyes. Isothermal temperature is facilitated by cartridge heaters embedded in an aluminum block, which holds the standard PCR tube as the sample container. The device is pocket-sized and operates on a 9V battery, making it ideal for low-resource settings. To demonstrate the operation of the device, loop-mediated isothermal amplification (LAMP) of Kaposi’s sarcoma herpesvirus (KSHV) is performed at 68℃. Fluorescence emitted by the intercalating dye in the reaction is measured in real-time by the micro spectrometer. KSHV quantification is obtained in as little as 30 minutes. The device is intended for simultaneous detection of multiple DNA targets in the field.