Siga Technologies ( SIGA - Get Report), a developer of antiviral medications, said it has received contracts from the Air Force worth $2.3 million. Under one contract valued at $1.4 million, Siga will develop counter-measures against potential biowarfare pathogens, the Dengue viruses and water-related viral agents for the Air Force Medical Service. The company also received a one-year contract worth $900,000 to aid the Air Force Special Operations Command in developing antiviral agents. Dengue fever and Dengue hemorrhagic fever are serious mosquito-borne diseases for which there are no approved drugs or vaccines. As a result, U.S. troops are vulnerable overseas and in areas affected by flooding, Siga says. Shares were up 6.3% to $4.21 Friday.