Chembio Diagnostics Inc. said Thursday that its losses nearly doubled in the final three months of last year compared with the same period in 2013 because of lower sales of its rapid tests for infectious diseases.

The Medford-based manufacturer of point-of-care tests for HIV and syphilis reported a loss of $496,000 for the October-December quarter. That represents a 47 percent increase from the fourth quarter of 2013, when losses totaled $262,000.

Sales in the final three months of the year totaled $7.1 million, a drop of almost 10 percent from the same time in 2013.

Chief executive John J. Sperzel said Thursday that the rising red ink was due in part to a big foreign order for tests in 2013 that wasn't repeated last year, and the company's decision to sell tests itself in the United States instead of through a third party.

He also said Chembio continues to pursue a strategy of extending its testing technology to the diagnosis of Ebola, dengue fever, malaria, febrile illness, traumatic brain injury and an undisclosed form of cancer. Last year, the company established partnerships with others to develop some of these new tests.

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For the year ended Dec. 31, Chembio reported a loss of $1.1 million compared with a profit of $531,000 in 2013. Sales were off 7 percent to $27.6 million.

Separately, Chembio reported having 166 employees at the end of last year in offices and a warehouse in Medford and Holbrook. That's almost a 20 percent drop from Dec. 31, 2013, when 206 people worked there.

Sperzel noted in the earnings report that the company had hired sales people last year to market its tests in the United States; much of its revenue stems from sales in Central and South America.

Chembio shares closed down 11 cents Thursday, more than 2 percent, to $4.02 on the Nasdaq exchange. They are up more than 5 percent in the past 12 months.