The Centers for Disease Control and Prevention in the United States described the Delta variant of the coronavirus as being as transmissible as chickenpox and warned that it could cause more severe disease, The Washington Post reported.

The US’ top health agency made these observations in an internal document that argues that officials must “acknowledge the war has changed.” It cites currently unpublished data as well as outside studies showing that vaccinated individuals infected with the Delta variant may be able to transmit the virus as easily as those who are unvaccinated.

Vaccinated people infected with Delta have measurable viral loads similar to those who are unvaccinated and infected with the variant, the document said.

The data cited in the document played a key role in revamped guidelines that call for everyone –irrespective of vaccination status – to wear masks indoors in public settings in certain circumstances, a federal health official told the newspaper.

On July 27, the CDC recommended that people inoculated against Covid-19 in high-risk parts of the United States should resume wearing masks indoors. This marks a change in masking guidelines in the United States. Earlier, fully vaccinated persons could gather indoors with other fully vaccinated people without wearing a mask or staying 6 feet apart.

CDC Director Rochelle Walensky confirmed the authenticity of the document and said people “need to understand that we’re not crying wolf here,” CNN reported.

“The measures we need to get this under control – they’re extreme. The measures you need are extreme,” she said.

Walensky told the channel that the data in the report did not surprise her. “It was the synthesis of the data all in one place that was sobering,” she said.

Rise in US Covid-19 cases

The latest seven-day moving average of daily cases in the US is 66,606, as per the CDC’s official data on July 30. This constitutes an increase of 64.1% compared with the previous seven-day moving average of 40,597.

The current 7-day moving average is 73.8% lower than the peak observed on January 10, 2021 (254,063) and is 480.1% higher than the lowest value observed on June 19, 2021 (11,483), the CDC said.

United States President Joe Biden said on Friday that “in all probability” new guidelines or restrictions would be imposed in the United States in response to the resurgence of Covid-19 cases, AFP reported.

He did not specify what steps could be taken.

The country’s federal government has tightened health regulations for its employees, who must now either be vaccinated or wear masks and be tested regularly, even in areas with low case numbers.