During 1906, with a force of 26,000, there were 21,739 cases of malaria admitted to the Commission Hospitals, and the death-rate from this disease was among whites 2 per thousand, among negroes 8 per thousand.
In 1907, with a force of 39,000, there were 16,753 cases, the death-rate among whites being 3 per thousand and among negroes 4 per thousand. The increase among whites was due to the greater proportion of the European labourers, whose circumstances are different from those of the skilled artisans and the "screened" clerical staff of Americans.
The total death-rate from all causes in 1907 is shown below:—
| Average Number. | Total Deaths. | Annual Death Rate per Thousand. | |
| White Employees | 10,709 | 179 | 16.71 |
| Black Employees | 28,634 | 953 | 33.28 |
| Total | 39,343 | 1,132 | 28.77 |
—but accidents account for a considerable proportion of the deaths.
During the same period the average number of American women and children in Commission quarters was 1,337, among whom occurred nine deaths, an average annual death-rate of 6.73 per thousand.
In addition to malaria there is one other disease which proves fatal to considerable numbers of employees, attacking principally the black labourers. This is pneumonia, to which are attributed altogether 328 deaths as against 154 from malaria.
It appears that special research is needed into the cause and prevention of this disease among negroes in the tropics.
In 1907 no less than 71,000 persons arrived on the Isthmus, all of whom had to pass the Commission doctor at the entrance port. All but transients are vaccinated on arrival, and great watchfulness is exercised against the introduction of any new disease from abroad. Thus, when bubonic plague broke out at Guayaquil, the Department of Sanitation commenced a campaign against rats as a precaution against the spread of the disease (which is propagated by the rat flea) in case quarantine measures failed to keep it out.