NEW YORK - Health officials say the delta variant of the coronavirus continues to surge and accounts for an estimated 83% of U.S. COVID-19 cases.

That’s a dramatic increase from the week of July 3, when the variant accounted for about 50% of genetically sequenced coronavirus cases.

“The best way to prevent the spread of COVID-19 variants is to prevent the spread of disease, and vaccination is the most powerful tool we have,” said Dr. Rochelle Walensky, director if the Centers for Disease Control and Prevention, during a U.S. Senate hearing Tuesday.

The delta variant is a mutated coronavirus that spreads more easily than other versions. It was first detected in India but now has been identified around the world.

––

HERE’S WHAT ELSE IS HAPPENING:

MEXICO CITY -- Authorities in Mexico say they have found fake doses of the COVID-19 drug remdesivir offered for sale on the internet and at a private hospital near the U.S. border.

The federal medical safety commission said late Monday that the fake antiviral drug, which it called “a health risk,” was found at a hospital in the Gulf coast city of Tampico, in the border state of Tamaulipas.

The commission said the doses had been purchased in an “irregular manner” on the internet but didn’t say whether the medication had been used there.

The drug’s manufacturer, Gilead Sciences, confirmed the falsification. The appearance and lot numbers on the packaging didn’t match the original.

The U.S. and Mexico have approved remdesivir as a treatment for COVID-19.

––––

WASHINGTON - The nation’s top infectious disease expert is suggesting parents follow new COVID-19 guidance for mask-wearing issued by the American Academy of Pediatrics.

The academy is recommending schools require face masks for children older than 2 and all adults - regardless of vaccination status. Dr. Anthony Fauci told “CBS This Morning” the academy wants to “go the extra mile” to make sure kids are protected at school because of the rise in cases blamed on the delta variant of the coronavirus.

That guidance is slightly different from the Centers for Disease Control and Prevention, which has advised mask-wearing in schools just for unvaccinated children and adults.

Fauci says the CDC is “carefully looking” at its COVID-19 school guidance.

–––

WASHINGTON - The United States has upgraded its travel warnings for Britain, Indonesia and three other destinations, advising Americans not to travel there due to a surge in coronavirus cases.

The CDC and the State Department issued revised advice to U.S. travelers Monday alerting them to the increased risk of contracting COVID-19 in Britain, Indonesia, Zimbabwe, Fiji and the British Virgin Islands. Previously, all had been covered by a less severe advisory to “reconsider travel.”

The advisories are recommendations that are constantly under review and are not binding, although they may affect group tours and insurance rates.

The warning for Britain, for example, has fluctuated between Level 3, or “reconsider travel,” and Level 4, or “do not travel,” several times this year already.

–––

JACKSON, Miss. - Mississippi’s top public health official says the state is seeing a rapid increase in coronavirus infections.

Dr. Thomas Dobbs tweets that the “4th wave is here.”

The Mississippi State Department of Health said Monday that 2,326 new cases were confirmed Friday through Sunday. That is largest three-day increase reported in the state since February.

Mississippi has one of the lowest coronavirus vaccination rates in the nation.

State Rep. Jeramey Anderson of Moss Point posted the Health Department numbers Monday on Twitter and lashed out at people who haven’t been vaccinated.

In the legislator’s words: “Consequences of not getting vaccinated and poor mask wearing. Well Mississippi - you wanted it here it is. This is ridiculous and the deaths that will definitely follow were completely avoidable.”

–––

TOPEKA, Kan. - The health department in the most populous county in Kansas is urging the county’s public schools to require students and staff who aren’t vaccinated against the coronavirus to wear masks indoors when classes resume for the fall.

The guidance Monday from the Johnson County Department of Health and Environment in the Kansas City area came with confirmed cases of the faster-spreading delta variant continuing to rise across Kansas and fueling larger numbers of new COVID-19 cases.

The state reported Monday that confirmed delta variant cases increased 20% since Friday, up 158 to 950.

State data also show that Kansas averaged 440 new COVID-19 cases for the seven days ending Monday.

–––

TORONTO - Canada says it will begin letting fully vaccinated U.S. citizens into Canada on Aug. 9, and those from the rest of the world on Sept. 7.

Canadian officials say the 14-day quarantine requirement will be waived as of Aug. 9 for eligible travelers who are currently residing in the United States and have received a full course of a COVID-19 vaccine approved for use in Canada.

Public Safety Minister Bill Blair said a date for the U.S. to allow fully vaccinated Canadians to cross the land border isn’t yet known. Any Canadian can currently fly to the U.S.