Shares of Chembio Diagnostics Inc. /zigman2/quotes/200199230/composite CEMI -1.50% rocketed 102% on heavy volume in premarket trading Wednesday, infectious diseases diagnostic company announced a $28.3 million purchase order its SARS-CoV-2 antigen tests from Brazil-based Bio-Manguinhos. Trading volume spiked to 22.3 million shares, compared with the full-day average of about 525,100 shares. The stock was the biggest gainer and most actively traded ahead of the open. Chembio's SARS-CoV-2 antigen test is designed to detect an active COVID-19 infection in 20 minutes using a nasal swab. The order from Bio-Manguinhos, a subsidiary of the Oswaldo Cruz Foundation, is for delivery during 2021. To put the $28.3 million order in perspective, Chembio recorded total revenue of $32.47 million in 2020. Benchmark analyst Bruce Jackson said the order win is "important" for the company, as it tries to improve its cash position and manage its working capital. The stock, which closed Tuesday at an 11-year low, has tumbled 56.6% year to date while the Nasdaq Composite /zigman2/quotes/210598365/realtime COMP -0.30% has gained 12.5% and the S&P 500 /zigman2/quotes/210599714/realtime SPX +0.02% has advanced 15.1%.