The House of Representatives will once again require all lawmakers and staff to wear masks inside, a sharp turnaround in policy as mounting fears about the Delta variant hit the front door of Congress. Senators are also encouraged to mask themselves, but are not required to do so.

In a memo late Tuesday night, Dr. Brian P. Monahan, Chief Medical Officer in Congress, he is recommending the change based on new CDC guidelines and the nature of the Capitol, which is mingling with thousands of people from across the country every week.

“For the congress, which is a collection of people who travel weekly from different risk areas (both high and low rates of disease transmission), everyone should wear a well-fitting medical filter mask (e.g. a KN95 mask) when they are are located in an interior, ”wrote Dr. Monahan to officials of the house.

In a letter to the senior senate leaders, Dr. Monahan gave the same advice but held no recommendation for a mask mandate. The Senate is a smaller body, and during much of the pandemic, its members voluntarily wore masks. Most of the senators are vaccinated.

Six weeks ago, the house triumphantly dropped its longstanding mask requirement to show optimism that the grip of the pandemic is loosening. Since then, at least one House MP and an assistant to Spokeswoman Nancy Pelosi have tested positive for the coronavirus after being fully vaccinated, and others on Capitol Hill have gone into voluntary quarantine after exposing people infected with Covid-19. At the same time, new cases have skyrocketed across the country.

Like wider mask policies by the CDC and aggressive interventions President Biden is considering to increase the country’s vaccination rate, the new mask mandate in the House of Representatives is likely to test the patience of a weary public and the Republican opposition party eager to Raise charges against Democrats who undermine confidence in vaccines and put the health of the recovering economy at risk. The Republicans in the House of Representatives immediately protested, with the prospect that they might refuse to comply.

“Make no mistake – the threat to return masks is not a science-based decision, but a decision conjured up by Liberal government officials who want to continue living in an eternal pandemic state,” said Rep Kevin McCarthy, Republican of California and the minority leader, wrote on twitter.

House rules state that any lawmaker who does not wear a mask in certain rooms of the Capitol Complex can be fined $ 500 or more. Several Republicans were fined for this reason earlier this year. However, it is unclear what Ms. Pelosi and other House leaders would do if many Republican members refused to participate. Democrats have been far more forgiving in the past, and many have resumed voluntarily wearing masks in the past few days.