1-Iraq is a less healthy place for Americans than Vietnam. Although both are tropical countries, Iraq and the Persian Gulf have long been known as less hospitable, heathwise, to Westerners.
2-More women serving in units. Women in the field, just like women in sports, suffer a higher rate of bone and muscle injuries than men. The reason is simple; men have thicker bones and more muscle mass to protect them while performing the frequent physical labor required in a combat zone.
3-The average age of troops in Iraq, because everyone is a volunteer and there are lots of reservists, is several years higher than the Vietnam war average of 23 years. Older troops, especially the many reservists in their 30s and 40s, are more prone to injury and illness.
4- Medical care has become more accurate in the past forty years and the armed forces are more likely to spot a problem earlier and act. Better diagnostic capabilities are sending troops home for conditions (early stages of cancer or other slow moving illnesses) that no one could have spotted in Vietnam.
Keep in mind that the Vietnam figures are averages for 13 years (1962-75) of action by American troops in and around Vietnam. During that period, some 2.8 million American troops served over there. Moreover, the level of combat activity varied considerably from year to year. Fighting didn't really get serious (for Americans), until 1966, when 6,053 died (including 1,045 non-combat deaths.) Deaths peaked in 1968 (16,511) and trailed off considerably from 1972 (when 561 died) to 1975 (when all American troops, mainly advisors and trainers) left.
The nature of combat was also quite different in Vietnam. There it was a civil war where one side (the communists) had adjacent nations (North Vietnam, Laos, Cambodia) that could be used for sanctuaries and major nations (Russia, China) supplying weapons, money and other support. As a result, most of the fighting was not against guerillas (who were largely wiped out in the 1968 Tet Offensive, a point largely missed by the American media at the time), but by North Vietnamese army units hiding in the South Vietnamese jungle. This kind of fighting involved a lot of helicopters, and 18 percent of American deaths were helicopter related (combat, and non-combat accidents.) This is more than twice the rate so far in Iraq. Same with the bombs and booby traps, which accounted for 12 percent of casualties in Vietnam, versus more than twice that rate in Iraq. The nature of the Vietnam fighting was largely gun battles in the jungle, and this was seen by the fact that, for the first time since the American Civil War, the majority of army combat deaths (61 percent) were from gunfire in Vietnam. The enemy didn't have a lot of artillery (as the foe did in Korea and the World Wars), so there were a lot of firefights in the bush. Iraqis are not very accurate with rifles, and U.S. troops have excellent body armor.
Finally, the reporting of casualties is different in Iraq. There is no "body count" (of enemy dead) mentality, a deliberate decision meant to avoid the mistakes encountered with that sort of thing in Vietnam. According to communist estimates (they admit they have no precise figures), guerilla and North Vietnamese army losses in South Vietnam were some 800,000 dead and 2.1 million sick and wounded. This is against 261,000 Allied combat deaths (mostly South Vietnamese), and 700,000 wounded. There were also 420,000 civilian deaths (mostly in the south) and 1.2 million injured. Iraq is very different, with much more precise firepower and many more journalists running around looking for the few civilian deaths that do occur. But the deaths among those attacking coalition troops is high, but deliberately not reported regularly by the military. However, every time there is an armed encounter with American troops, a detailed report is prepared. This is used to determine if current tactics and procedures could be improved and, if so, the changes are made within hours, or days. While the number of Iraqi attacker deaths are not made public, the higher fees paid to the attackers by Baath Party leaders and increased use of remote controlled bombs indicates that getting too close to American combat troops is seen as a losing proposition. But even the remote controlled bombs are not the perfect weapon. The analysis of each incident generates new tactics for detecting and avoiding them. This battle of wits largely goes unreported, as does an accurate comparison of the casualties, and tactics in Vietnam.
Since March, American troops in Iraq have been suffering about .9 percent casualties (dead, wounded, or hospitalized for non-combat causes) a month. During the nine year Vietnam war, the rate was 44 percent higher (1.3 percent a month). Moreover, during Vietnam, combat caused sixty percent of the injuries, while in Iraq, combat has only caused 23 percent of the injuries. Thus U.S. troops in Iraq are suffering .21 percent combat casualties a month compared to more than three times the rate (.78 percent) during the Vietnam war. The non-combat injury rate in Vietnam (.52 percent a month) was actually lower than the rate in Iraq (.69 percent). Much of this difference is accounted for by four factors;