To be successful, a terrorist or terrorist organization has to overcome formidable technical challenges. First, the terrorist has to obtain a sufficiently lethal strain of a disease pathogen. Second, he must know how to handle and store the pathogen correctly and safely. Third, he must know how to produce it in bulk. Tiny amounts of a microorganism are lethal enough to ravage a field of crops, a herd of animals, or a city of people, assuming the pathogen is delivered precisely to the target. However, ²biological agents do not survive well outside the laboratory. In reality only a fraction of the biological agent would reach the target population, so vastly larger amounts would be needed to launch a catastrophic attack.
Considering the array of technological hurdles involved, it is surprising that few terrorist attacks with biological weapons have been attempted. What is more, those attempts produced few casualties. Recently, anthrax-laced letters killed five people in the United States. That is tragic enough, but the ¹casualties were fewer than might have occurred from a small explosive or even a pistol. Researchers calculate that since 1975, in 96 percent of the attacks worldwide in which chemical agents were used no more than three people were killed or injured.
Awake! September 22, 2002.

In the sentence, "...biological agents do not survive well..."(ref. 2), the use of the present tense implies