A method of determining whether a test sample contains Dengue virus, said method comprising the steps of: (a) obtaining nucleic acids from the test sample; (b) performing an in vitro nucleic acid amplification reaction using the nucleic acids obtained in step (a) as templates for amplification with a set of primers, wherein the base sequence of a first member of said set of primers consists of the target-hybridizing sequence of SEQ ID NO: 1 and, optionally, an upstream promoter sequence and/or an upstream tag sequence, wherein the base sequence of a second member of said set of primers consists of the target-hybridizing sequence of SEQ ID NO:10 and, optionally, an upstream promoter sequence and/or an upstream tag sequence, wherein neither of said upstream promoter sequences nor said upstream tag sequences, if included, can hybridize to the nucleic acid of any of Dengue virus serotypes 1-4 and participate in said in vitro nucleic acid amplification reaction in the absence of joining to said target-hybridizing sequence, and wherein the base sequences of a third member and a fourth member of said set of primers respectively consist of SEQ ID NO:13 and SEQ ID NO:16; and (c) detecting any of said amplification product that may have been produced in the in vitro nucleic acid amplification reaction, whereby detecting said amplification product determines that the test sample contains at least one of Dengue virus serotypes 1-4, and whereby failing to detect said amplification product determines that the test sample does not contain Dengue virus. (a) obtaining nucleic acids from the test sample; (b) performing an in vitro nucleic acid amplification reaction using the nucleic acids obtained in step (a) as templates for amplification with a set of primers, wherein the base sequence of a first member of said set of primers consists of the target-hybridizing sequence of SEQ ID NO: 1 and, optionally, an upstream promoter sequence and/or an upstream tag sequence, wherein the base sequence of a second member of said set of primers consists of the target-hybridizing sequence of SEQ ID NO:10 and, optionally, an upstream promoter sequence and/or an upstream tag sequence, wherein neither of said upstream promoter sequences nor said upstream tag sequences, if included, can hybridize to the nucleic acid of any of Dengue virus serotypes 1-4 and participate in said in vitro nucleic acid amplification reaction in the absence of joining to said target-hybridizing sequence, and wherein the base sequences of a third member and a fourth member of said set of primers respectively consist of SEQ ID NO:13 and SEQ ID NO:16; and wherein the base sequence of a first member of said set of primers consists of the target-hybridizing sequence of SEQ ID NO: 1 and, optionally, an upstream promoter sequence and/or an upstream tag sequence, wherein the base sequence of a second member of said set of primers consists of the target-hybridizing sequence of SEQ ID NO:10 and, optionally, an upstream promoter sequence and/or an upstream tag sequence, wherein neither of said upstream promoter sequences nor said upstream tag sequences, if included, can hybridize to the nucleic acid of any of Dengue virus serotypes 1-4 and participate in said in vitro nucleic acid amplification reaction in the absence of joining to said target-hybridizing sequence, and wherein the base sequences of a third member and a fourth member of said set of primers respectively consist of SEQ ID NO:13 and SEQ ID NO:16; and (c) detecting any of said amplification product that may have been produced in the in vitro nucleic acid amplification reaction, whereby detecting said amplification product determines that the test sample contains at least one of Dengue virus serotypes 1-4, and whereby failing to detect said amplification product determines that the test sample does not contain Dengue virus. whereby detecting said amplification product determines that the test sample contains at least one of Dengue virus serotypes 1-4, and whereby failing to detect said amplification product determines that the test sample does not contain Dengue virus.