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been effectually excluded. The authorities fully appreciate the danger of the introduction of yellow fever from Mexican ports, and very thorough precautions are taken. After studying the local conditions and arrangements in Honolulu I am of opinion that the port affords a strong protection against the infection of Asia and the East Indies.
(2) On the usual route to 'Hong Kong the ships, after leaving Honolulu, pass northwards into latitudes not as a rule favourable to the life of mosquitoes, and the remaining ports of call are Yokohama and other Japanese ports and Shanghai. There is a serious gap in our knowledge of the conditions in these ports, for we do not yet know whether stegomyia fasciata occurs in them or not.. If it is present, and sufficiently abundant, the introduction of the yellow fever virus might lead to an epidemic, but the climate is such that the disease would entirely die out during the winter, and fresh importation would be necessary for its reappearance.
(3) The climate of Hong Kong is more favourable to the existence and spread of yellow fever, but again we are ignorant of the presence or absence of stegomyia fasciata there. In all probability a thorough search during the hot months would show that it is present, but quite possibly it is not very abundant.
(4) The route from San Francisco viâ Honolulu to the Philippines does not necessarily take ships northward to Japan, but until San Francisco or Honolulu becomes infected such a route is not a cause for anxiety.
On the whole we must conclude that the present routes are not very favourable to the infection of Asia, and it only remains to endeavour to foretell whether future routes will be more so. On this subject Major Tucker has suggested that ships from the Panama Canal may follow a more southerly route, calling perhaps at Christmas Island instead of at Ionolulu, and being, during the whole voyage, in a climate favourable to mosquito life. Such a change of route would not, however, be adopted unless it materially shortened the journey, which is fortunately not the case. In this connexion it is important that ships crossing the Pacific usually follow as far as possible what are called the Great Circle sailing tracks, which are considerably shorter than the Mercatorial tracks, and that those tracks often take them into latitudes much higher than those of the ports between which the ships sail. For example, the shortest route between Panama (latitude 9° N.) and Manila (latitude 14° N.) is a great circle track which passes for about 1,000 miles of the journey above the 40th degree of north latitude; and the shortest between Panama and Hong Kong (latitude 22 N.) is a track which passes for about 800 miles of the journey above the 44th degree of north latitude and afterwards touches Yokohama. The distance between Panama and Hong Kong by that route is about 330 miles shorter than by a route which, on a chart on the Mercator Projection, would be represented by a straight line between the two ports. It will be apparent, therefore, that ships from the Panama Canal will, in all probability, go northward to Yokohama not only on account of the trade with Japan, but because such a course is the shortest that can be followed; and it will be clear that the fact that vessels follow those tracks materially lessens the risk of the conveyance of mosquitoes across the Pacific.
The climate of the present route from Salina Cruz to Tahiti for New Zealand and Australia is, of course, favourable to mosquitoes, but I have already mentioned the possibility that the canal may attract the traffic which now departs to those countries from that port; if this happens it will, in my view, lessen the present risk that the ships may start their voyage with infected mosquitoes on board.
II. Recommendations.
Although the facts and considerations summarized in the foregoing section must, I think, lead to a modification of the opinions hitherto held regarding the degree of danger of the spread of yellow fever to the East and to India as a result of the opening of the Panama Canal, it cannot be too strongly urged that they do. not justify the conclusion that little or no action is at present necessary.
(1) In the first place it must be emphasised both that the knowledge obtain- able for the purpose of forecasting the situation that will arise after the canal is opened for traffic is unavoidably incomplete and imperfect, and that at any time after the opening of the canal there may occur unexpected events which would alter the whole position. From the circumstances of the case the knowledge that can be obtained at present is insufficient to enable us to do more than conjecture what changes, in the distribution of yellow fever in the endemic area what
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increased traffic to the East, and what measures to prevent ships from carrying infection, will follow the opening of the canal. And although it has been shown in Section I. that, in all probability, India will not be in danger until some of the countries further East become infected, it seems to me essential that she should be supplied with continuous information upon those subjects. It is, of course, even more urgent that such information should be available to our Far Eastern colonial ports, which, as I have shown, are more directly exposed to the risk of infection.
For these reasons my first recommendation is that permanent arrangements should be made to obtain continuous first-hand information regarding the yellow lever situation in the endemic area, the actual shipping traffic in that area, the actual shipping traffic from and through the area to the East, and the measures that are taken to prevent ships from carrying infection. So far as I can learn, the only satisfactory method of obtaining this information is to station perma- nently in the endemic area a medical officer who will be constantly in touch with the Consular and quarantine officers of the United States and other countries. I therefore strongly advocate the appointment of such an officer. In practice he would be attached for duty to the British Consulate at Panama, and his work would chiefly be that of an intelligence officer in the endemic area. By acting in co-operation with the Consular and sanitary officers of the United States, by visiting suspicious places, and by making a special study of the local and trans-Pacific shipping, he would quickly become aware of any new circumstances which threat- ened the safety of the East. He would, of course, keep a continuous record of the shipping from the endemic area to the East, and would ascertain the risk of infection to those ships. He might, as a rule, report his transactions monthly, but he would also be empowered to cable at any time to the quarantine officers in Eastern ports such information as would enable them to take adequate precautions against any threatened danger.
Supplementary to that measure it is highly advisable, I think, to appoint a second medical officer as an intelligence officer in an area of which Hong Kong would be the centre. He would be stationed in Hong Kong, and one of his first duties would be to become thoroughly familiar with the shipping which enters that port from the endemic area, and with the history of the voyages of such ships; but he would also place himself in frequent written communication with the sanitary authorities of the Philippines, and, if necessary, would visit Manila in order to ascertain exactly what new of increased dangers may have arisen to those islands as a result of the opening of the Panama Canal, and what steps are taken for their protection. In the same way he would endeavour to watch the situation in its relation to Shanghai. In Hong Kong itself he would associate himself with, and assist in, any measures that may be taken for the better pro- tection of the port and for the safety of ships which leave the pört for Singapore and India; and by his reports to the central organisation presently to be men- tioned India would be constantly informed of any new circumstances of a threat- ening character in regard to the spread of yellow fever, as well as of the progress of any enquiries such as that relating to the presence or absence of stegomyia fasciata, Following this plan further, it would doubtless be of great advantage, though
it is not perhaps essential, to appoint a third intelligence officer with headquarters at Singapore, and with permission to visit the chief ports in Sumatra, Java, and Borneo, for purposes similar to those already mentioned.
The scheme here advocated is not a new one, for the United States, with a view to ensure the safety of their ports, has for some years extensively employed the practice of attaching officers of the public health service to the American Consulates in foreign ports; and it has been found to be by far the most satis- factory method of obtaining trustworthy and complete information, and of exer cising control over ships bound for the United States from those ports. I believe that, if somewhat similar action on the part of Great Britain were to be taken in the manner that I have suggested, the countries concerned would welcome the co-ope- ration of the officers appointed, and that its adoption would be a reasonable and effectual safeguard to the Fast and to India.
(2) In the second place it must be recognised that, as is shown in other sections of this report, we have very little or no knowledge not only upon the subject of a sure method of diagnosing yellow fever, but upon such subjects as the presence or absence and distribution of stegomuia fasciata in eastern colonial and other ports. the problem of whether the very widely distributed and abundant species, stegomyia
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