The average strength of the garrison was 5,654, exclusive of colonial troops. There were 5,167 admissions into hospital (914/1000 mean strength), with 37 deaths (6.53/1000 mean strength), of which 24 occurred in hospital, 10 out of hospital and 3 among the invalids on their passage home and at the Invalid Depôt at Netley. 131 invalids were returned to the Invalid Depôt at Netley; 111 were discharged from the service. The majority (27) of the invalids were sent home for tubercular disease, while 22 had a circulatory disorder.
The average number constantly sick was 255 men, excluding the Royal Malta Fencible Artillery. The ratio per 1000 mean strength constantly sick was 45.10; the average sick time to each soldier was 16.46 days; the average duration of each case was 18.01 days.
During the year, miasmatic diseases from infections accounted for 2,070 admissions into hospital (366.1/1000 mean strength) with 9 deaths (1.59/1000 mean strength). Admissions were for:
- 61 admissions for parasitic conditions
- 45 for tubercular diseases with 4 deaths
- 246 admissions for respiratory conditions with 1 death
- 317 admissions for digestive diseases with 2 deaths
- 149 admissions for nervous system diseases with 4 deaths
- 71 admissions for circulatory diseases with 2 deaths
- 15 admissions for urinary problems with 1 death
- 301 admissions for venereal diseases
- 722 admissions for accidents with 8 deaths
18 soldiers were admitted to hospital after receiving corporal punishment. There were 1 suicide, 1 homicide and 1 execution. The homicidal death was that of a sergeant 1st/22nd Regiment who was shot by a private of his regiment. Five of the accidental deaths were from drowning, three were found drowned and two drowned after the capsizing of a pleasure boat.
There were 25 admissions for paroxysmal fevers (4.4/1000 mean strength), 1,057 for continued fevers (186.9/1000 strength) with 6 deaths (1.06/1000 strength), 290 for dysentery and diarrhoea (51.3/1000 strength) with 3 deaths (0.53/1000 strength), 342 for ophthalmia (60.5/1000 strength), and 182 for Rheumatism (32.2/1000 strength). There were 6 admissions for eruptive fevers, predominantly small pox, with no deaths. Continued fevers were most prevalent from June to September. Medical officers blamed their rise to the great heat of the summer, exposure of the men to the direct rays of the sun and defective drainage.
The increase in the number of venereal diseases, mainly from primary and secondary syphilis, was attributed by the Principal Medical Officer to the arrival in Malta of the women who followed the troops from the Ionian Islands upon their evacuation by the British Forces.
The winter of 1864 was unusually cold. All the inhabitants particularly the country folk, who slept in rooms directly opening into yards, were more exposed to the intense cold. Several districts were afflicted with measles and smallpox, both diseases raging through the villages of Zejtun, Zurrieq and Safi.