What measures do Catholic dioceses take at Mass during viral outbreaks?

Many people around the world have transmitted and contracted COVID-19 in physical Churches. Therefore, in-person Mass is cancelled until further notice.

Your local parish may have virtual Zoom services, so I recommend you visit your local parish's website during this quarantine period.

I'm in England. "The Catholic Church in England and Wales has issued national guidelines" (BBC, 2020-03-05).

Do not rely on my answer for safety advice. The latest Coronavirus (COVID-19) Guidelines are available online, from the Catholic Bishops Conference of England and Wales.

I quote Version 3 (2020-03-09). At this time it says we are officially at Stage 2: A number of cases in local communities or a case specifically linked to a parish community. Stage 2 starts:

1. It is likely you will need to suspend distribution under both kinds (the host to be given on the hand only).

   a. When giving communion in the hand seek to ensure you place the host in the hand of the recipient in such away that you do not touch their hands.

2. Suspend the physical sign of peace.

3. Remove holy water stoups.

4. Public veneration of relics and the Cross on Good Friday should NOT be by kissing or physically touching them.

5. Advise those most vulnerable (elderly, people with weakened immune systems and long term conditions like cancer, diabetes and heart disease) to refrain from large parish gatherings and stay at home.

   [The 2020 outbreak of COVID-19 poses an extremely high risk to the elderly, and several other groups. The UK government has stated that people over 70 would soon be advised and supported to isolate from the general population].

6. Cease use of shared hymnbooks and missals which could help transmit the virus.

[... and there is more ...]

For the benefit of my irreligious ignorance: the first two measures sound similar to the 2018 article, "Catholic diocese [of Down and Connor] suspends 'sign of peace' due to flu" (2018). And on the first point, Wikipedia has a definition for Communion under both kinds.

Your question also asks how they will make announcements, and set appropriate expectations. I don't think these guidelines say very much about that.

Ask every one attending Mass to sanitise their hands as they come into church using sanitized gel dispensers. [...]

...maybe their asking "as [you] come into church" means you would have a chance to ask also, if there is something specific you are concerned about. But I don't know.

display the public information poster, which states ["catch it, kill it, bin it", "Do not touch your face" ...]

[...] Ask anyone with cold or flu symptoms to refrain from attending

Under these specific guidelines, suspending public Mass and other gatherings is described as Stage 3: Many Cases in local parishes. This stage is reserved unless or until "public authorities will give general advice on suspending large public gatherings."

Current UK government advice has not yet reached this stage. There has been some unclear communication - briefings from government sources without specific attribution.

"Downing Street signalled it was preparing to stop large public events, including sports fixtures and concerts, to alleviate the pressure on police and the ambulance service. It did not specify what size of event would be affected, and the timing of the clampdown has yet to be decided, but it is expected to come into force in a week’s time." - The Guardian, 2020-03-13.

The Conference also published a separate FAQ document, which ends with:

11. How will I know if/when the Church changes its advice?

Any new or changed information will be posted on the Bishops’ Conference Website and posted on the Ad Clerum.

What measures do Catholic dioceses take at Mass during viral outbreaks?

First of all it will depend on the severity of a particular outbreak in a particular geographical location or diocese.

For the most part, a particular national conferences of bishops would make up some general guidelines for a particular ecclesiastical region. Nevertheless a local ordinary is always free to impose further measures (within reason) for his own subjects in his own (arch)diocese during certain circumstances.

At the moment there seems to be no official statement of particular measures from the US Conference of Catholic Bishops itself, for the coronavirus outbreak.

For example, I live in the archdiocese of Vancouver and a few years ago, His Grace asked that the ”sign of peace” should be suppressed during a rather nasty flu outbreak that had hit Vancouver and adjoining areas.

Up here, pastors generally announce any changes of the Mass itself (at least for the first time) at a convenient moment at Mass, since most parishioners do not read the weekly bulletins prior to Mass. Most bulletins will have fuller information for the faithful to peruse in their own time at home. This is how we do things here.

As a token of what guidelines are being implemented I am going to refer to what the US dioceses are doing in light of the Covid-19/Coronovirus outbreak. Canada will follow similar protocols.

Dioceses nationwide are taking precautions to guard against the spread of the coronavirus and reminding parishioners to take commonsense steps related to hygiene in their personal lives.

Among the most common preventative measures being taken are urging reception of holy Communion in the hand, suspension of distribution of the Communion cup and exchanging the sign of peace without physical contact.

Diocesan leaders also asked people who are ill to refrain from attending Mass.

“If you are sick, stay home until you are feeling better,” Bishop David A. Zubik of Pittsburgh said in a March 2 announcement to parishioners.

In a Feb. 28 letter, Charlotte Bishop Peter J. Jugis urged clergy to remind parishioners to cover coughs and sneezes and throw away used tissues, clean all “high-touch” surfaces daily, avoid shaking hands, wash hands often and not share personal items such as cups and eating utensils.

Like diocesan officials across the U.S., Jugis encouraged priests not to extend the sign of peace, distribute Communion from the cup or invite people to shake hands in greeting at Mass or other gatherings. Those who distribute holy Communion should wash their hands before Mass and clean their hands again before and after distributing Communion, he said.

Similar precautions were being implemented in the Archdioceses of Washington and the dioceses of Jackson, Mississippi, and Little Rock, Arkansas.

Beyond those steps, the Archdiocese of Miami suggested that parishes empty the holy water fonts at church entrances, and it also is allowing extraordinary ministers of holy Communion who feel uncomfortable in carrying out their ministry to temporarily step down.

Guidelines from the Ohio Department of Health for dealing with contagious illnesses were reviewed in a statement shared with parishes and posted on the Diocese of Cleveland’s website March 2.

The diocese’s Office for Worship also reminded priests, deacons and extraordinary ministers of holy Communion to continue practicing good hygiene including frequent hand washing.

Archbishop John C. Wester of Santa Fe, New Mexico, updated liturgical practices introduced in January because of the severity of the flu season in Utah. In a March 3 statement, he mandated that holy Communion be received in the hand.

“What is important is that we receive our Blessed Lord in holy Communion,” he said. “How we receive, while very personal to the individual communicant, is not crucial. … Receiving Communion in the hand is every bit as respectful as receiving on the tongue.”

At the U.S. Conference of Catholic Bishops, Msgr. J. Brian Bransfield, general secretary, March 3 requested in an email to staff that they “refrain, until further notice, from planning any new international travel.” - U.S. dioceses adopt wide-ranging plans to limit spread of coronavirus

Other countries have taken further measures for Mass and while at Catholic liturgies and customs, as seen by the following:

Italy has become the center of Europe’s coronavirus outbreak and Catholic bishops there have responded by cancelling Mass and encouraging the faithful to watch services from home. The Vatican has temporarily closed the Italian catacombs.

The changes to Catholic worship practices are overlapping with the observance of Lent, a 40-day period of reflection and renewal before Easter. Near the end of Lent, many Roman Catholics mark Jesus’ death on Good Friday by kneeling and kissing the cross.

In the Philippines, bishops have advised parishioners to instead genuflect and bow to the cross on Good Friday. It remains to be seen if U.S. bishops will follow suit. - Catholic Churches Are Emptying Holy Water Fonts Over Coronavirus Concerns

What changes are made at Masses around the world because of outbreaks like the Covid-19/Coronovirus outbreak?

In Germany:

• Since January or February, Holy Water is no longer available near the doors of the Church because of Corona (*).
• Until January, the faithful were shaking the hands with next persons when "may the peace with you" was said after the High prayer. Since January or February, the faithful were asked not to do this but to use other ways of greeting during Corona season. (*) Since the end of the "lock-down", shaking hands is forbidden. (**)
• In Germany many faithful already used the host-to-hand variant instead of the host-to-tongue variant to receive the Communion since it was tolerated it in the 1970s. In January or February the remaining faithful were urgently asked also to use the host-to-hand variant. (*) Since the "lock-down" the host-to-hand variant is mandatory. (**)
• In most parts of Germany the number of faithful who can attend a mass is limited. Therefore, a seat reservation is mandatory to attend a mass in some parishes (example: Sunday masses in the cathedral of Cologne). (**)
• The faithful have to wear a mask during the mass. (**)
• Faithful are forbidden to sing in some parts of Germany. (**) In such parishes a small choir observing special Corona restrictions may sing.
• (Not caused by the diocese:) Many faithful attend a mass being broadcasted on TV instead of physically going to a church.

(*) Situation in the diocese Rottenburg-Stuttgart in Corona time before the "lock-down" (announced in a letter from the bishop).

(**) Restriction decided by dioceses because otherwise state laws would be violated; because Germany is a federal country with different laws in different states, this might not apply to all parts of Germany.