There is the letter from the Rebbe by the six-day war that your not allowed to change your plans to not go to Eretz Yisroel or to leave early. So is there the same problem here?
The second part of the question is that maybe just the opposite, cause it says in Gemara that in a time of a מגפה (pandemic) you should ran to the desert, so maybe it’s just the opposite & it would be a obligation to leave, so as to stay safer.
(In Yeshiva in Eretz Yisroel you don’t have the ability to keep clean – which is a main part to not catch the virus, & even if ח”ו you get it will be better taken care of at home where you have a caring mother etc.)
One may leave Yeshiva or seminary in EY early based on doctor’s recommendations and consistent with the support of the local hanhalah.
(Personally, I am skeptical whether the medical information contained in your letter – that it’s easier to contain, manage or care for the virus at home – is accurate).
To The best of my knowledge, the Rebbe never wrote during the six-day war that it was forbidden to leave EY early. In the series Iggros Kodesh, no such letter appears.
There is an unsubstantiated rumor that the Rebbe told Rashag on Shavuos 5767 during the Seudah, that his approach was based on a Torah prohibition. The Rebbe, however, clarified immediately that he chose not to label it as an issur.
It should be noted that it is a well-known fact that the descriptions of the conversations that took place during the Seudos are highly inaccurate and unreliable. Even if we would assume that it’s indeed true that leaving at that time Involved an issur, this was due to the prohibition of not instilling fear during a time of war. This does not apply to someone who is taking medical precautions and leaving the country based on a medical recommendation.
Obviously, one has to take into account the effect this will have on the student learning, the extent of the bittul Torah and how will impact the other students in the school. All of this has to be measured against the severity of the medical issue at hand. This is why it’s extremely important to consult with a medical practitioner as well as with the hanhalah.