Both the CDC and the FDA are working on how to best update Covid vaccines to target circulating variants annually, similar to flu vaccine campaigns.

Measles is one of the most contagious human viruses and is almost entirely preventable through vaccination.

Senior staff at the US Centers for Disease Control and Prevention told investigators Trump aides bullied staff and tried to rewrite reports in a bid to align guidance with the president's downplaying of the crisis.

As recently as March, the CDC recommended against travel to about 120 countries and territories worldwide, or more than half of all destinations.

The green light for the use of redesigned Omicron Covid boosters will enable millions of the retooled shots to roll out as part of a nationwide revaccination campaign.

Deaths from Covid-19 contributed to half of the overall decline in life expectancy last year, with drug overdoses and heart disease also major contributors, data shows.

A document provided by the agency says an external report into its response found public guidance had caused confusion, while important information was sometimes released too late to inform federal decisions.

The agency says it no longer recommends unvaccinated people quarantine after exposure, adding that 95% of the US population has either been vaccinated or had Covid-19 already, or both.

The discovery of the disease from wastewater samples collected in June means the virus was present in the community before a confirmed case was made public July 21.

Polio symptoms include flu-like symptoms such as a sore throat, fever, tiredness and nausea, the CDC says.

Despite the rise in cases, the new variants should not be allowed to cause panic or 'disrupt our lives,' President Joe Biden's chief medical advisor Anthony Fauci says.

CDC estimates that between 2015 and 2019 about 80 to 130 distinct flights annually warranted at least one contact investigation 'compared to more than an estimated 25,000 distinct flights in 2020' and 17,000 passengers.