Gerhard Henrik Armauer Hansen

Gerhard Henrik Armauer Hansen's discovery of the Mycobacterium leprae was historic for reasons beyond its significance to the fight against leprosy. As the first identification of a bacteria as the causative agent of a human disease, his study was a precursor to Robert Koch's conclusive demonstration of the bacterial cause of anthrax three years later. Although Hansen was unable to cultivate the leprosy bacillus in vitro as an experimental confirmation of his hypothesis. It has still not been done, and this is the reason why it has not been possible to develop a vaccine. His research helped to establish fundamental principles in immunology, bacteriological medicine and public health policy.

Gerhard Henrik Armauer Hansen was the eight of fifteen children. His mother was Elizabeth Concordia Schram, who was a member of a family of master joiners long established in Bergen. His father, Claus Hansen, was a wholesale merchant until the severe contraction of credit in 1848-1851 drove him into bankruptcy. He then worked as a cashier in a bank.

In 1859 Hansen worked his way through the gymnasium and medical school. He began his medical studies at the University of Christiania (now Oslo). It was necessary for him to earn his own living while he was as student. He first taught at a girl’s school and later spent a year as substitute for the prosector in anatomy. He then began his own tuition courses in anatomy. In later years he said that during this period he had known neither physical nor mental fatigue and had found that he did his best work between six and eight in the morning. He passed his degree with honours in 1866, having already proved himself an exceptional research talent. He completed his internship at the National Hospital in Christiania (Rikshospitalet). He then served as doctor to a fishing community of some 6.000 inhabitants at Lofoten, a string of Islands off northern Norway.

In 1868 Hansen returned to his native town of Bergen, the centre for Norwegian leprosy research. At this time the disease was still a social problem in Norway, with some 3,000 patients for whom 800 nursing places were reserved. In Bergen alone there were no less than three lepra hospitals.

Here Hansen entered service at the Pleiestiftelsen for spedalske nr 1. He soon moved on to the position of assistant physician at the Lungegaardshospitalet under Dr. Daniel Cornelius Danielssen. With C. W. Boeck Danielssen in 1847 had published the major work Om Spedalskhed (On Leprosy). His efforts in organizing Bergen's leprosy care program had helped to establish Bergen as the European centre for leprosy research. Danielssen was a foremost authority on the clinical and pathological aspects of the disease but, like other investigators of the time, regarded the affliction as hereditary, a belief he continued to hold even after Hansen's discovery. Many physicians believed the disease to be caused by miasma.

Hansen later wrote that he had never before seen so much misery in one place. Because the lepers were so disfigured and stunted, they were outcasts. Both Danielssen and Hansen travelled around to attended to the sick, which were often isolated in remote farms where nobody helped, and collect material. The disease was not uncommon in western parts of Norway in the nineteenth century.

Hansen quickly concluded on the basis of epidemiological studies that leprosy was a specific disease that must have a specific cause, not an inheritable plague holding man hostage. He was convinced that a bacterium carried the disease from person to person; a daring speculation at a time when the concept of contagion was still poorly understood, and no one had shown that bacteria could cause human diseases.

Challenging Danielssen's authority, Hansen in one of their first meetings declared his views, and thus ran into a professional, but in no way personal conflict with his superior. The fact that the number of new leprosy cases was diminishing, Hansen saw as a support for his theory and the efficacy of measures taken against contagion.

However, his relationship to Danielssen improved, and Hansen was able to commence his research, comprising both experimental and epidemiological efforts. In his first work, of 1869, published in Norwegian only in 1871, Hansen among other things described the appearance of leprous changes in lymphoid tissue. Here Hansen applies the term ”infectionsstoff” (“infectious substance”) for the changes he saw in association with lymph nodes. He was, however, very uncertain about what these findings really meant. His poor equipment complicated his work, and he was unsuccessful in his attempts to cultivate and stain the changes.

In 1870 a grant allowed Hansen to travel to Bonn and later to Vienna for advanced training in histopathology. Returning to Norway, using primitive staining methods and working with biopsy specimens from patients with leprosy, Hansen continued his intensive microscopy work.

On his return to Bergen in 1871 Hansen launched his search for the causative agent of leprosy, using biopsy specimens drawn from patients.

A physically strong and unflagging young man, Hansen decided to look for bacteria in patients, first in blood, and on finding none, in skin nodules. He wrote:

At that time . . . I could sit tirelessly for hours on end, focusing through the microscope with great enlargement . . . One day I was positive I had discovered the bacteria, the next day magnificent certainty had collapsed, and I would be back where I started . . . Finally, though, I wrote the first record of my research.

In every nodule he saw rod-like bodies inside cells that looked like bacteria; they were not present in all cells, but in most of them. At first he was unable to see rods in patients with tuberculoid leprosy, but after prolonged studies he found them there also. He could not see any difference between these bodies and true bacteria, but hedged on claiming they were actually identical.

In 1873, aged 32 years, he discovered the rod-shaped bodies - Mycobacterium leprae, sometimes called Hansen’s bacillus, in leprous nodules. This epoch-making discovery was published in his major work of 88 pages that year. Most of his colleagues and physicians elsewhere laughed. Hansen, they said, may have seen these bodies in tissues, but it did not mean they caused disease. It did.

His findings were also published in English in an abridged edition. His description of the findings is rather careful:

“Though unable to discover any difference between these bodies and true bacteria, I will not venture to declare them to be identical”

This carefulness on Hansen’s side certainly contributed to the priority conflict which was soon to blossom.

By 1879 he was able, through the use of improved staining methods, to show great numbers of the rod-shaped bodies typically aggregated in parallel cells. He believed the bacillus to be the causative agent of leprosy and thereby became the first investigator to suggest that microorganisms might cause a human disease. The tuberculosis bacillus, for example, was not discovered until 1882.

The Neisser-Hansen conflict of priority.
In the beginning of 1879 Hansen was visited by the German bacteriologist Albert Neisser, then 24 years old, who was on a research trip to Norway to study leprosy. Neisser was able to examine more than 100 patients with leprosy in Trondheim, Molde, and Bergen. From Hansen he received preparations made from lepra node in which unstained rode were just recognizable.

Back home in Germany Neisser in a very convincing way was able to stain the bacteria, and found, in almost all cases, "bacilli as small, thin rods, whose length amounts to about half the diameter of a human red blood-corpuscle and whose width I estimate at one-fourth the length." Neisser did not hesitate to publish his results, without first contacting Hansen, in the paper Über die Aetiologie des Aussatzes (1880). In a paper Neisser writes:

Having quickly returned home with this wealth of material, I immediately began to study it, and to my intense surprise found bacilli in large numbers . . . These rods appeared to be something previously unknown . . . The singularity of their appearance awakened the hope that further investigations might bring light to an obscure question.

At the same time, In Bergen, Hansen, with the help of new methods, also succeeded in staining his preparations.

In the following year, 1881, Neisser published the article Weitere Beiträge zur Aetiologie der Lepra in Virchows Archiv in which he claimed the honour of discovering a microbe that caused disease, and sought to discredit Hansen. There is no doubt that Neisser intended to steal Hansen's discovery, and might well have succeeded.

The priority conflict is to some extent a parallel to that between the French discoverer of the HIV virus, Luc Montagnier at Pasteur Institute, and the American Robert C. Gallo, who falsely claimed credit for the discovery.

However, Norwegian reaction to Neisser’s behaviour was indignation, particularly because the term Neisser’s bacteria was soon in use. Encouraged by his colleagues, Hansen defended his position, though without entering into a direct polemic. Instead, he summarized his findings from the beginning of the 1870s and published them in Norwegian, German, English, and French. He described Neisser's visit to Bergen, and stated firmly that he was making the report to maintain his priority, and bring his work up to date.

The conflict proved to be long lasting, and it was not until a lepra congress in Berlin that Hansen in an international context was officially recognized as the true discoverer of the lepra bacillus. It is clear, however, that while Hansen first discovered the leprosy bacillus, Neisser was the first to identify it as the etiological agent of the disease. The aetiology, diagnosis, and prophylaxis of leprosy occupied Neisser for much of his subsequent career.

In 1955, George L. Fite and Herbert W. Wade reviewed the Hansen-Neisser controversy in depth. They commented that:

When one looks back at Neisser's first article and begins to realize the situation, one can understand how Hansen must have felt about it. He could scarcely have failed to be infuriated. Neisser started by discrediting Hansen, who had willingly shown him everything he could and had surely, been instrumental in providing Neisser's material. Far from genuinely giving Hansen any credit, Neisser spent much effort to assert the importance of his organisms as against Hansen's.

In his memoirs, written 30 years later, Hansen claims he took Neisser's move to pre-empt his discovery without excitement. He wrote that his chief, Danielssen was furious, and dressed him down severely for not responding more aggressively to this deliberate attempt to steal his idea.

Fite and Wade did not believe that Hansen understood the full import of his discovery, since the paper he published in 1879 did not contain much more information than the one published in 1874. They thought Hansen had done little additional work, and that inadequately.

Ethics
The fault was not Hansen's. Unlike most bacteria causing human diseases, scientists have been unable to culture Mycobacterium leprae on artificial culture media. This was true in 1879 and is still true today. Hansen was also unable to infect rabbits. It would be almost 100 years before Polly's armadillos would supply the animal host and bountiful supply of bacilli that Hansen needed.

His failure to grow the bacillus or infect rabbits had bitter consequences. In a less well-advised effort, Hansen inoculated the eye of a woman suffering from a neural form of the disease with material drawn from a leprous nodule of a patient suffering from the cutaneous form. There were no clinical consequences of the inoculation, but the woman claimed it was painful and impaired here sight. She took her case to court. According to the records of the city of Bergen Law Courts, May 31, 1880:

He did not succeed in inoculating the material into the eye, as she did not keep the eye still. One of the other doctors . . . calmed down the despondent and placed her in a chair. It was then possible to carry out the operation, placing the material from the cataract knife under the conjunctiva of the eye . . . The defendant . . . admitted that he had neither obtained her permission in advance, nor told her of his aim in doing it.

The defendant then explained his motives for this unjustified operation . . . He said he had failed in his attempts to infect animals. Thus he could not prove that his rod shaped bacilli caused leprosy; so he could not quarantine patients to protect the people of Bergen.

The court found him guilty. Hansen had to pay costs, and was removed from his post as resident physician of the Bergen Leprosy Hospitals in May 1880. After the trial he made no major contributions to research.

Hansen’s sentence was less severe than it might seem, however, since he was allowed to retain his position as leprosy medical officer for the entire country of Norway - an appointment conferred on him in 1875 and one that held until his death. He was thus able to implement changes in the methods of control of leprosy in Norway - changes that had been in part made necessary by his own hypothesis concerning the aetiology of the disease. The Norwegian leprosy act of 1877 and the amended act of 1885 were the fruits of his untiring work. Under these laws health authorities could order lepers to live in precautionary isolation away from their families (subsequent studies have shown leprosy to be a familial affliction); enforcement of the law led to a quick and steady decline of the disease in Norway. There were 1.752 known cases of leprosy in Norway in 1875; by the beginning of the twentieth century there were 577. The last outbreak in Norway was in the 1950's. During the last five years of the twentieth century four cases were reported in immigrants from other parts of the world, and there are now 1-2 such cases each year. This, however, is the tuberceloid form, which is generally a skin disease and not contagious. All cases having been treated, there are presently nobody with the chronic form of lepra in Norway. The word «hansenarium was suggested to replace the still more standard «leprosarium».

Twice married
Hansen married Danielssen’s daughter, Stephanie Marie, "Fanny", on January 7, 1873. Only a few months after the wedding it was discovered that she was infected with pulmonary tuberculosis. Like all her three sisters, who also died from the disease, she had been infected by her father. The disease had a fast course and she died on October 25 of the same year. On August 27 1875 he married Johanne Margrethe Tidemand, a widow related to almost the entire Bergen Commercial patriarcate. She brought two children into their marriage. Their only child, a son, was named Daniel Cornelius Armauer Hansen for Hansen’s superior and previous father-in-law. The son became a physician specializing in tuberculosis and in 1929 was appointed chief of the tuberculosis hospital in Bergen. The first period after the birth of their son, Hansen's second marriage was happy. However, his wife soon started complaining that her husband neglected her for his scientific work. Still, the couple had a large social circle among the intellectuals of the city, counting the composer Edvard Grieg and his wife Nina among their closest friends. It was said that the marriage successively became one only in the name, and that his wife wanted to divorce him in order to marry a musician named Iver Holter.

Hansen had an open mind for the themes of his times and, among other things, contributed money from his own pocket to pay for a visiting lecture by the Danish author Georg Brandes on the Romantic period in France. He also enjoyed theatre, often attending performances in the metropoles of Europe when on his numerous travels abroad. Over the years Hansen developed a distance to his native country, which he came to consider “lay outside the world." His autobiography indicates a resignation over the mental condition and cultural views of his countrymen.

Armauer Hansen suffered from syphilis
For the better part of a century after his death, only his family knew of the fact that Armauer Hansen suffered from syphilis, contracted from a consenting seamstress in Christiania during his student years in the 1860s. At the age of 36, in 1877, he suffered a brain stroke, which may have been provoked by this disease.

Hansen suffered the first symptoms of heart disease as early as 1900. In the following years he had several severe heart attacks that confined him to bed for long periods of time. In the intervals of his illness, however, he continued to travel around the country on official inspection tours. In February 1912 he made such a trip to the fishing areas north of Bergen. In Florø, a little town on the western coast, he was invited to stay in the home of a friend, and it was there that he died. He was given a funeral at state expense; he had been president of the Bergen Museum and the ceremony took place from its hall.

A Darwinian blasphemer in Bergen
While Hansen was chiefly known for his work on leprosy, he also played a role in the dissemination of Darwin’s ideas. Early in his career, during his stay in Vienna Hansen was introduced to the teachings of Charles Darwin, and then set about to study Darwin’s books. In Darwinian doctrine he discovered a scientific ideal, particularly in its methodology of dispassionate observation. In 1886 he published a book on Darwinism in Norwegian. In his apostolic zeal for Darwin’s work, Hansen also gave numerous lectures and published articles in the popular press. These evoked a great sensation, especially from the clergy and religious organizations - who reacted violently against the «blasphemer» in their midst. Hansen was, however, devoid of philosophical speculations and had no aptitude for martyrdom. He did not acknowledge the attacks made against him; he continued to sit at his microscope, smoking his pipe, and do his work.

The uncomfortable radical
Armauer Hansen was a radical in his time, an atheist with a hostile attitude to the church. Among other things he was indignant of the preaching of guilt by the clergy, which he considered to hamper the development of society. All through his life he was an oppositional. Whilst a medical student he stopped attending the lectures because he thought he understood things better than his teachers. Hansen sometimes was considered rigid in his views and was not known to be a flexible debater.

However, people in his closest circle described Hansen described as an amiable, warm-hearted and entertaining person void of superior manners and personal ambitions.

In the final chapter of his autobiography Hansen presents strings of thoughts that certainly mirror his personality. He questions whether religion will prevail among men and predicts that the puzzle of the origin of life will be solved in the twentieth century. He supports workers demands for a larger share of production value and expects socialism to be carried out in some modified form. At the same time, however, he was extremely critical of women’s emancipations, considering the role of men founded in his superior physical and mental capacity, thus doubting whether women were fit to become doctors.

Hansen considered the two most important scientific events in his lifetime to be Pasteur’s discovery of the importance of microbes and Darwin's theory of evolution.

Power to the people
Hansen saw the need for bringing scientific results to a broader public. Over many years he wrote numerous papers of popularised science and was a prolific lecturer. As an organization man he was active in various bodies, like the board of the Bergen Museum, Selskabet for de norske Fiskeriers fremme (Society for the Advancement of Norwegian Fisheries), and Det medicinske selskab i Bergen (Bergen Medical Society). Hansen was one of the founders of the journal Medicinsk Revue, later to be ranamed Nordisk Medicin, of which he was one of the editors for many years.

Honours and awards
Hansen received many international assignments and honours for his leprosy studies. He was president of honour of the section for dermatology and syphilis at the international medical congress in Copenhagen in 1884.

He served as chairman of the International Leprosy Committee, and in 1897 was elected honorary chairman of the first Conférence Internationale de la Lèpre, held in Berlin, and was president of the second such conference, held in Bergen in 1909. The meeting was something of a peak in Hansen’s scientific career. Here he was acclaimed as the discoverer of the lepra bacillus and one of the foremost figures in suggesting measures to prevent the spread of the disease. He was honorary chairman of the International Leprosy Committee, corresponding or honorary member of numerous scientific societies, and was decorated several times. In 1900 contributions toward a portrait bust of Hansen were solicited internationally; the bust, made by Jon Visdal, was unveiled with great ceremony the following year in the museum garden, now the university garden, in Bergen.

In 1892 he received the St. Olavs Orden (Order of Saint Olav) for scientific contributions and two years was conferred doctor of honour at the University of Copenhagen. In recognition of scientific and administrative contributions, Hansen in 1901 was given a rise of wages corresponding to that of a professor of the highest degree, by Stortinget – the Norwegian parliament.

Dear armadillo
Hansen never achieved Koch’s fame, since he could not grow his bacillus in the test tube or infect animals. His attempt to inoculate a woman demonstrates his desperation. Since then some five generations of scientists have striven in vain to grow Hansen's bacilli. Without them, it was impossible to develop vaccines and diagnostic reagents, or find out how disease is transmitted. Thus, leprosy lingered in the shadow of medieval medicine for another century.

A major advance in experimental leprosy occurred when Eleanor Storrs reported a leprosy infection in the nine-banded armadillo. During the course of obtaining normal tissues from captured armadillos, some animals were found to be infected with acid-fast bacilli similar to Mycobacterium leprae.

These findings caused considerable public and scientific controversy in America. The possibilities of an infected animal escaping from the experimental farm, insect vectors or healthy animals scavenging on dead animals were all proposed to explain the transmission of leprosy disease to armadillos.

Unfortunately, some sceptics questioned the validity of experimental infection of armadillos with M. leprae and suggested that the Louisiana workers were detecting the indigenous disease. This view has not prevailed. USPHS banished Storrs from leprosy research before this controversy was resolved. Yet, her discovery revolutionized research on all aspects of the disease.

A few armadillos can supply enough of the once scarce reagent, lepromin, to meet the world’s needs. NIH has funded a program top map the genome of the leprosy bacillus. Trials are in progress on 470,000 people in India, Malawi, and Venezuela on armadillo-derived vaccines. A recent WHO report describes a broad spectrum of programs in immunology and biochemistry made possible by her vision.

Storrs also dispelled an ancient stigma. Her finding of leprosy in wild armadillos, stilled those who claimed leprosy was a curse of God, visited only on sinners.

Hansen’s name is attached to the Armauer Hansen Reasearch Institute in Addis Ababa in Ethiopia, which was established by the Norwegian and Swedish Save the Children foundation. Today the University of Bergen is the main financial supporter of the institute, which does basic research on lepra, particularly its immunology.

Attached to the Institute is a village of cured lepers, whose stigma makes it impossible for them to return to their own villages.

During a visit to the institute in 1980, the editor of this dictionary experienced a moment of happiness for two elderly men. After they hade been through their cure, which included operations, the doctor had ordered them to retrain the muscles of their face. This they did by making faces at each other in a mirror. Unfortunately, the opportunity knox agent was not there.

And: next time you are in Baton Rouge, Louisiana, USA, visit The National Hansen’s Disease museum.

We thank Patrick Jucker-Kupper, Switzerland, for information submitted.

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• Tabeller over de Spedalske i Norge i Aaret 1880 samt Oversigt over Spedalkshedens Gang 1856-1880.
  Christiania 1882. 4- 3 Bl. 41 sider.
  På side 15-18: Skrivelse fra Overlægen for den spedalske Sygdom.
• Bacillus leprae.
  [Virchows] Archiv für pathologische Anatomie und Physiologie und für klinische Medizin, 1880, 79: 32-42.
• Recherches sur les Annelides recueillies par M. le professeur E. van Beneden pendant som voyage au Brésilet à la Plata.
  Bruxelles 1881. 4. 29 sider med 7 lith. Pla.
  (Edouard van Beneden, 1856-1894. Professor in Lüttich)
• Terminaison des nerfs dans les muscles du corps de la sansue.
  (Travail du laboratoire d'histologie du Collège de France.)
  M. 1 Træsnit. Archives de physiologie, 2ème sér. 1881, T. VIII: 739-741.
• Studien über den Bacillus leprae.
  [Virchows] Archiv für pathologische Anatomie und Physiologie und für klinische Medizin, 1882, 90: 542-548.
• Hr. Jerome Buchholz og den spedalske Smitteagtitation.
  Dagbladet 1882 nr. 278. I Den norske Nordhavs-Expedition 1876-1878, Zoologi, skrev Armauer Hansen:
  
• Annelinda. Christiania, 1882. 54 sider.
  
• Spongiadæ. Bind XII. Christiania 1885.
• Einige Bemerkungen über die anästhetische Form des Aussatzes.
  Vierteljahrsschrift für Dermatologie und Syphilis, Prag (fortsettelse av Archiv für Dermatologie und Syphilis), 1883, X: 557-560.
• Nogle ord om Darwinisme og Udviklingslæren.
  Dagbladet 1883 nr. 330. Foranlediget av en artikkel av F. Lohmann i Morgenbladet nr. 268 B.
• Die Ätiologie und Pathologie der Lepra.
  Vierteljahrsschrift für Dermatologie und Syphilis, Prag, 1883, XI: 317-316. Avtrykk av ovennevnte foredrag ved Lægemødet i Kjøbenhavn.
• Om de senere Undersøgelser af Baciller ved Spedalskhed.
  Norsk Magazin for Lægevidenskaben, 3. Række. 1883, XIII: 256-259.
• Soppsygdomme.
  Medicinsk Revue, 1884, I: 161-169, 193-199 og 225-232.
• Biologiens Betydning for det medicinske Studium.
  Medicinsk Revue, 1884, I: 321-325.
• Tvangslov og Stiftelser mod Spedalskhed
  Polemik mod Dr. N. Wulfsberg i Tidsskrift for praktisk Medicin, V. 1885, No. 15.
  Medicinsk Revue, 1884, II: 295-290.
• Den nye Lov om Spedalskhed.
  Medicinsk Revue, II: 351-364.
• Kort oversigt over de patogene Soppe
  (Foredrag i det 1ste vestlandske Lægemøde med Demonstration).
  Medicinsk Revue, Extranummeret, side 144-145.
• Mikrober, ptomainer og leukomainer.
  Medicinsk Revue, IV: 14-17.
• Den medicinske Undervisning.
  Medicinsk Revue, IV. side 56-63.
• [Artikkel om den nye loven om spedalskhet].
  Bergens Aftenblad 1885 for 20. august.
• Bericht über zoologische Untersuchungen in den Sommeren 1884-85 auf Kosten des Museums vorgenommen.
  Bergen Museums Aarsberetning for 1886, side 48-54.
• Die Aetiologie und Pathologie der Lepra. M. 1 Pl.
  Compte-rendu du congrès international. Copenhague 1884. Copenhagen, 1886. T. III. section de dermatologie et de syphilidelogie. Side 27-40.
  Foredrag var forbundet med Demonstration af 3 fra Bergen medbragte Spedalske.
• Die Lage der Leprabacillen.
  [Virchows] Archiv für pathologische Anatomie und Physiologie und für klinische Medicin, Berlin, B. 1886, 103: 388-392.
• Den naturvidenskabelige vantro.
  Nyt Tidsskrift. 1886, V: 283-303.
• Instinkt og Intelligens.
  Nyt Tidsskrift, 1886, V: 833-845.
• De praktisk-videnskabelige Undersøgelser betræffende Saltvandsfiskerierne.
  Bergensposten 1886 nr. 57. Kfr. svar av Carl Lumholtz i nr. 72 og gjensvar av Hansen i samme nr.
• Afstamningstheorien eller Darwinismen.
  Bergensposten 1886 nr. 59.
• Tankelæsning. Bergensposten 1886 nr. 235.
• Nekrolog over Konservator J. Koren.
  Bergen Museums Aarsberetning for 1886, side 5-8.
• Afstamninsteorien eller Darwinismen.
  Bergen 1886. 8. 84 sider. Med 2 Tavler.
• La septicémie inoculée `des baleines par les flèches, dont se servent les pêcheurs.
  Archives de Biologie (utgitt av van Beneden og E. van Beneden), 1887, VI: 585-587.
  Etter et foredrag ved Naturforskermødet i Christiania 1886. Se Forhandlinger, side 141.
• Lidt om lægeforholdene i Amerika.
  Medicinsk revue 1888, side 353-356.
• Om sygdommes arvelighed. Medicinsk revue, 1889, side 38.
• Om arvelighed. Naturen 1889, side 133-145.
• Forebyggelse af tæring. Naturen 1889, side 193-195.
• Dyrs og menneskers faste. Naturen 1889, side 268-269.
• Stivkrampe. Naturen 1889, side 349.350,
• Vore viktigste næringsmidlers bestanddele. Naturen 1889, side 353-358.
• Metschnikoffs fagocytteori.
  Medicinsk revue, 1889, side 44-47.
• Om desinfektionsovne med demonstration af tegninger og modeller.
  Forhandlinger paa 3. norske lægemøde, 1889, side 68-71.
• Lidt om disposition til sygdomme.
  Medicinsk revue, 1889, side 321-326.
• Sansning hos de lavere dyr. Naturen 1890, side 27-28.
• Spedalskhedens udbredning. Naturen 1890, side 38-44.
• Bacillenes giftighed. Naturen 1890, side 125.
• Uddrag af skrivelse fra overlægen for den spedalske sygdom, dateret Bergen 24. og 31. desember 1891. Beretning om de spedalske i Norge i femaaret 1886-1890, side 126-129. 1891.
• Nogle bemerkninger om immunitet.
  Medicinsk revue, 1891, side 113-114.
• Om uimodtagelighed for smitsomme sygdomme – immunitet.
  Naturen 1891, side 106-109.
• Unitarismen. Samtiden 1891, side 272-278.
• Om sygdommes arvelighed.
  Forhandlinger paa 4. norske lægemøde 1891, side 19-25.
• Leprøse testikler.
  Festskrift i anledning af overlæge Danielssen 50-aarige embedsjubileum, 1891, side 21-29. På side 1-4: dedikation.
• Latens af sygdomsgifte.
  Medicinsk revue, 1892, side 171-178.
• Det menneskelige øre. Naturen 1892, side 65-68.
• Moskestrømmen. Naturen 1892, side 271-274.
• Kolera. Naturen 1892, side 274-275.
• Tuberkulosespørsmaalet. Medicinsk revue, 1893, side 65.
• Brown-Séquards indsprøitninger.
  Naturen 1893, side 48-51.
  Refererer til forsøk på å forynge seg selv med innsprøytninger av ekstrakt av testikler fra marsvin og hunder. Den franske fysiologen Charles-Édouard Brown-Séquard (1817-1894) skadet sitt gode navn og rykte stygt da han 1. juni 1889 presenterte en "sensasjonell" rapport om dette til Société de Biologie i Paris.
• Oversigt over de nyere studier over immunitet.
  Naturen 1892, side 172-175.
• Kemotaxi. Naturen 1892, side 371-372.
• Foranstaltniger mod lepra og tuberkulose.
  Medicinsk revue, 1894, side 73-78 og 144.
• Die Lepra vom klinischen und pathologisch-anatomischen Standpunkte.
  Sammen med Carl Looft. Bibl. med int, 1894, bind II, nr. 2.
• Pasteur og hans betydning for den biologiske videnskab.
  Naturen 1894, side 12-23.
• Behandling af sygdomme med blodvand – serumterapien.
  Naturen 1894, side 310-313.
• Leprastudiets fremtidige stilling i vort land.
  Medicinsk revue, 1895, side 1-5.
• En ny hypotese om dyre- og plantearters liv og forsvinden.
  Naturen 1895, side 36-38.
• Om disposition til sygdom.
  Medicinsk revue, 1895, side 321-325.
• Spedalskheden paa Island.
  Medicinsk revue, 1895, side 5-6 og 365-366.
• Leprosy. In Its Clinical and Pathological Aspects.
  With Carl Looft. Bristol, 1895.
• Uddrag af skrivelse fra overlægen for den spedalske sygdom, dateret 13. januar 1896. Beretning om de spedalske i Norge i femaaret 1891-1895, side 134-136. (Om sygdommens aftagen m.v.)
• Tuberkuloseloven.
  Tidsskrift for Den norske lægeforening, 1896, side 482-484.
• Ang. foranstaltninger mod tuberkulosen – tilsvar til dr. C. Benneche.
  Medicinsk revue, 1896, side 29-32 og 72.
• Kampen mod de smitsomme sygdomme.
  Naturen 1896, side 135-141.
• Dampskibe for vestlandske distriktslæger.
  Medicinsk revue, 1896, side 227-229.
• Teorier om arv. Naturen 1896, side 1-13.
• Arv af erhvervede egenskaber.
  Naturen 1896, side 109-115 og 169-176.
• Om spedalskhed. Hospitalstidende, København, 1896, 103-107.
• Om spedalskhed. Ugeskrift for læger, 1896, side 154-155.
• Nekrolog over professor Hjalmar Heiberg.
  Medicinsk revue, 1897, side 257-259.
• Lepra. Klinisk og patologisk-anatomisk fremstillet.
  Med Carl Looft. Bergen, 1897. 92 sider.
• Telegrafering uden traad. Naturen 1897, side 117-118.
• Lidt om spedalskhed. Naturen 1897, side 324-336.
• Forholdet mellem tuberkulose og lepra.
  Skandinaviske naturforskeres forhandlinger. 14. møde, side 509-515.
• Leprosy in Norway. International medical annual 1897. Nogre lepraspørsmaal. Medicinsk revue, 1897, side 324-325.
• I anl. af stadsfys. Bøckmans bemerkninger (dvs om Cornets forsøg).
  Medicinsk revue, 1898, side 196-197.
  Referring to the French physician Georg Cornet (1858-1915), who first demonstrated tubercle bacilluses outside the body. This discovery was important for public prophylactic measures against tuberculosis.
• Spedalskhedens overførelse.
  Medicinsk revue, 1897, side 297-298.
• Lægernes lønning.
  Tidsskrift for Den norske lægeforening, 1898, side 407-409.
• Gjensvar til H. Dedichens art.: Kan tanken tænkes materiel?
  Medicinsk revue, 1899, side 15-17.
• Mikrobegifte og slangegifte. Naturen 1898, side 151-154.
• Immunitet. Naturen 1898, side 161-164.
• Norsk folkepsykologi. Ringeren 1899, nr. 38.
• Lepraens bekjæmpelse.
  Medicinsk revue, 1900, side 106-108.
• Kræftens aarsagsforhold.
  Medicinsk revue, 1900, side 293-300.
• A rare case of leporsy.
  Lepra, Bibliothèque internationales, 1900, I, side 3.
  Hansen var medlem av redaksjon av dette verket fra dets begynnelse.
• Kræftparasiter. Naturen 1900, side 188-191.
• On the prevention of emigraton and immigration of lepers.
  Lepra, Bibliothek internationales, 1900, I: 88-89.
• Nutidens hygiene. Naturen 1901, side 19-22.
• Havbunden. Naturen 1901, side 379-386.
• Uddrag af skrivelse fra overlægen for den spedalske sygdom, dateret 18. april 1902.
  Beretning om de spedalske i Norge i femaaret 1896-1900, side 111-112.
• Vor melkeforsyning. Medicinsk revue, 1902, side 11-14.
• Lidt om medicinens udvikling i det 19. aarhundre.
  Naturen 1902, side 46-51.
• Rudolf Virchow. Naturen 1902, side 289-293.
• Medicinsk skole i Bergen.
  Medicinsk revue, 1902, side 177-181.
• Indstilling fra beriberikomiteen.
  Medicinsk revue, 1902, side 298-300. Innstilling om dette på side 384-385 og 415.
• Dr. Armauer Hansen at a meeting of the leprosy committee in London.
  Polyclinic, London, 1902. Ref i lepra III, 1903, side 260-263.
• Medicinsk skole i Bergen.
  Medicinsk revue, 1902, side 346-348.
• Arv eller nydannelse? Naturen 1903, side 308-312.
• Den medicinske undervisning.
  Medicinsk revue, 1903, side 193-200.
• Lepra.
  In Wilhelm Kolle and August Wassermann, editors, Handbuch der pathogenen Mikroorganismen, II. Jena, 1903: 178-203.
• Korrespondance.
  Lepra, Bibliothek internationales, 1903, III: 231.
• Filosofi og akademisk undervisning.
  Medicinsk revue, 1903, side 295-197. Svar til R. Vogt.
• Fiskespiser som spedalskhedens aarsag.
  Medicinsk revue, 1904, side 163-168.
• Paraleprose.
  Deutsche medizinische Wochenschrift, Berlin, 1904, nr. 38
  (festhefte til 5. internationale dermatologiske kongress i Berlin.
  Trykt i Lepra 1905, V: 76-77.
• Abnahme der Lepra in Norwegen.
  Lepra, Bibliothek internationales, 1904, IV: 235-240.
• Om paraleprose.
  Foredrag ved 11. norske lægemøde 1905.
  Tidsskrift for Den norske lægeforening, 1905, side 831-835.
• Spedalskhed. Naturen 1906, side 308-312.
• Zu Hutchinsons Fischtheorie. Lepra, Bibliothek internationales, 1907, VIII: 27-28.
  (Sir Jonathan Hutchinson, English surgeon and pathologist, 1828-1913)
• Leprosy in Finmarken.
  Lepra, Bibliothek internationales, 1907, VII: 209-210.
• Die Geschichte der lepra in Norwegen.
  Sammen med H. P. Lie.
  Lepra, Bibliothek internationales, 1908 VIII, Supplementary volume, pp. 314-340.
• Medicinsk maalstræv og folkeskolens naturkundskabsundervisning.
  Norsk magazin for lægevidenskaben, 1908, side 477-478.
• Heredity of leprosy.
  Festskrift til Cæsar Boeck. Archiv für Dermatologie und Syphilis, Berlin, 1911, CX: 225-232.
• † Max Johan Losting. Medicinsk revue 1911, side 248.
• Albert Neisser:
  Ueber eine der Gonorrhoe eigentümliche Micrcoccenform.
  Centralblatt für die medicinischen Wissenschaften, Berlin, 1879, 28: 497-500.
• Albert Neisser:
  Über die Ätiologie des Aussatzes.
  Jahresbericht der Schlesischen Gesellschaft für Vaterländische Kultur, Breslau, 1880; 57: 65-72.
  Neisser obtained leprosy tissue from Hansen and, using aniline dyes for staining Mycobacteriae leprae, was able to demonstrate it more convincingly than Hansen.
  Weitere Beiträge zur Aetiologie der Lepra. [Virchows] Archiv für pathologische Anatomie und Physiologie du für klinische Medixin, 1881; 84: 514-542.
• G. A. Hansen
  Livserindringer og betraktninger. Albert Neisser:Kristiania: Aschehoug & Co, 1910.
• G. A. Hansen:
  The Memories and Reflections of Dr. G. Armauer Hansen.
  German Leprosy Relief Association (DHAW), 1976.
• W. H. Feldman:
  Gerhard Henrik Armauer Hansen. What Did He See and When?.
  International Journal of leprosy.
• G. L. Fite, H. W. Wade:
  The contribution of Neisser to the establishment of the Hansen bacillus as the etiologic agent of leprosy and the so-called Hansen-Neisser controvery.
  International Journal of leprosy, 1955, 23: 418-428.
• Th. M. Vogelsang:
  Armauer Hansen - Leprabasillens oppdager. Hans liv og hans livsverk. 1968. Kobro:
  Gerhard Henrik Armauer Hansen.
  Annals of medical history, 1925, VII, nr. 2.
• E. Waaler:
  Patologi og mikrobiologi i Bergen. Det første sentrum for lepraforskning.
  Nordisk medicinsk årsbok. Supplement XI. Stockholm: Medicinhistoriska museet.
• Johanne-Margrethe Patrix:
  Gerhard Armauer Hansen. Leprabasillens oppdager.
  Eide Forlag A/S, 1997.
  The author is the granddaughter of Gerhard Armauer Hansen, and the daughter of Daniel Cornelius Armauer-Hansen.
• G. L. Fite, G.L. and H. W. Wade:
  The contribution of Neisser to the establishment of the Hansen bacillus as the etiologic agent of leprosy and the so-called Hansen-Neisser controversy.
  International Journal of Leprosy, 1955, 23: 418-28.