The Covid 19 virus is a serious concern, but not nearly as lethal as many epidemics that have struck Jewish, and non-Jewish, communities in years past.

Compared to the Black Death — which had a 50 to 70 per cent mortality rate — this new coronavirus, which has a mortality rate of little over two per cent (although this figure is disputed and could be significantly lower), seems a lot less scary. But rapidly spreading disease forces us all to decide how to respond. And we do not always respond well.

In 1863, builders working on the Rue des Juifs in the town of Colmar, close to where France borders Germany and Switzerland, discovered a treasure trove hidden behind a wall. The rings, broaches and coins had been hidden by a Jewish family in 1348, as the Bubonic plague swept through Europe.

It seems the treasure’s owners intended to return after the plague had passed, but succumbed themselves; perhaps of the plague, or perhaps as a result of the anti-Jewish persecution that followed in its path.

A 14th century history of Strasbourg contains an account of the confession of ‘Agimet the Jew’, who under the influence of “a little torture”, admits placing poison in the wells of Venice and Toulouse. Colmar is only 50 miles south of Strasbourg, location of one of the most vicious anti-Jewish massacres on Valentine’s Day 1349.

Not even good ideas, in the face of dangerous disease, guarantee safety. And the presence of dangerous disease can result in very bad ideas appearing dangerously attractive.

Jewish religious leaders speak with rare unanimity when it comes to the necessity of placing best-practice medical advice at the heart of our response to dangerous diseases, even at the expense of the weightiest religious observances.

Rabbi Yisrael Salanter, one of the most important leaders of 19th century Lithuanian Jewry, insisted Jews break the Yom Kippur fast during the cholera epidemic of 1848. One account even suggested the great rabbi made kiddush in the synagogue as an example to encourage anyone who might errantly prioritise fasting over consumption of fluids at a time of great danger. But sometimes even knowing the best way to treat a disease is not enough.

Researching Jewish attitudes to epidemics, I came across an article by the rabbi and medical doctor, Edward Reichman.

The article was illustrated with a photograph of the author in a full Hazmat suit. He was working at one of New York’s designated ebola receiving hospitals, doing a “don” and a “doff” of the protective clothing on a daily basis.

The article considered the Jewish legal response to a number of very tough challenges. Must a doctor place themselves at risk if called upon a treat a patient with a deadly contagious disease? How much risk must one accept in order to save the life of another?

The Biblical verse calls on all “not to stand idly by as the blood of your brother is shed”, but most legal authorities agree that a person cannot be commanded to place themselves at risk in order to save someone else.

Covid 19 is certainly less deadly than ebola but, as a congregational rabbi, I am already getting questions about whether certain congregants should be barred from attending synagogue, even if government advice is not that they should self-isolate.

Another rabbi and medical doctor, Aaron Glatt, of Young Israel Woodmere, New York, and South Nassau Communities Hospital, gave a recent lecture on Covid 19.

“Several great poskim [legal authorities] have personally told me that one must stay home and not go to shul if you are sick with a potentially contagious respiratory illness,” he said, before calling for regular handwashing and good personal hygiene.

“At this time,” Dr Glatt said, “We do not have a strict recommendation against hand shaking or kissing the sefer Torah or mezzuzos for people who are not at all sick. Use common sense.” Common sense is, of course, meant to be a marker of good Jewish legal teaching, at all times.

After the epidemic of cholera that swept London in 1850, the Jewish community held a prayer service. The ‘Form of Prayer’ read as follows: “Your hand lay heavily on the inhabitants of this land. Cholera struck many down.

The strongest heart trembled at the voice of death sounding at the threshold, and the boldest among the mighty were seized with terror and anguish. But gracious and merciful are You; Your wrath does not last long, nor does Your anger last for ever.

You strike some and heal. You wound, but it is Your hand which prepares the calm. In the depths of our terror and affliction You sent Your spirit and there was a pause. You commanded, and the Plague ceased.”

May we never have need of such a prayer.

Jeremy Gordon is Rabbi of New London Synagogue (Masorti)