Other scholars have expressed doubts about whether the attempt was effective. McConnell (1992) argued the smallpox outbreak among the Indians preceded the blanket incident, with limited effect, since Indians were familiar with the disease and adept at isolating the infected. Ranlet (2000) wrote that previous historians had overlooked that the Delaware chiefs who handled the blankets were in good health a month later; he believed the attempt to infect the Indians had been a "total failure." Dixon (2005) argued that if the scheme had been successful, the Indians would have broken off the siege of Fort Pitt, but they kept it up for weeks after receiving the blankets. Medical writers have expressed reservations about the efficacy of spreading smallpox through blankets and the difficulty of determining if the outbreak was intentional or naturally occurring.