What is the Islamic perspective on contagion?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

There are many different narrations in which the Prophet, sallallaahu ‘alayhi wa sallam, spoke about the issue of contagion. Amongst these narrations are:

1-    It was narrated on the authority of Abu Hurayrah, May Allaah Be Pleased with him, that the Prophet, sallallaahu ‘alayhi wa sallam,  said: “‘There is no ‘Adwa (contagion, transmission of infectious disease without the Permission of Allaah), nor Safar (the month of Safar was regarded as “unlucky” during the Jaahiliyyah), nor Haammah (refers to a Jaahili Arab tradition described variously as: a worm which infests the grave of a murder victim until he is avenged; an owl; or the bones of a dead person turned into a bird that could fly).’ A Bedouin stood up and said, ‘Then what about the camels? They are like deer on the sand, but when a mangy camel comes and mixes with them, they all get infected with mange.’ The Prophet, sallallaahu ‘alayhi wa sallam, said, ‘Then who conveyed the (mange) disease to the first one?’” [Al-Bukhari and Muslim]

2-    Also, it was narrated on the authority of Abu Hurayrah, May Allaah Be Pleased with him, that the Prophet, sallallaahu ‘alayhi wa sallam, said: “Do not put a sick one with a healthy one”.

3-    In another narration: “Flee from the leper as you would flee from a lion."

4-    It was narrated on the authority of Abu Hurayrah, May Allaah Be Pleased with him, that the Prophet, sallallaahu ‘alayhi wa sallam, once ate with a leper, and said: “Out of trust in Allaah and reliance on Him."

Scholars differed in reconciling between the above-mentioned Hadeeths. The most correct of these opinions is that the diseases cannot cause infection by themselves. However, Allaah The Almighty Is The only One Who Makes them cause and transmit infection.

Ibn Hajar, May Allaah Have mercy upon him, in an attempt to reconcile between these Hadeeths, said, “What is meant by negating contagion is that nothing can cause infection by itself, refuting what the people of the pre-Islamic era claimed. They believed that the diseases can communicate themselves from one person to another without the Permission of Allaah. So, the Prophet, sallallaahu ‘alayhi wa sallam, refuted this idea and ate with the leper to prove that Allaah The Almighty Is The only One Who Can Bring illness and Grant health, and forbade them from thinking in this way to clarify that they are just causes that may have effects. In his prohibition, the Prophet, sallallaahu ‘alayhi wa sallam, proves that there are causes but rather they cannot affect by themselves and Allaah The Almighty Is The only One Who, if He Wills, Can Allow them to have an effect or not."

Allaah Knows best.