Members of the 1st Tennessee wait to take part in in a demonstration of a battle during ongoing activities commemorating the 150th anniversary of the Battle of Gettysburg, Friday, June 28, 2013, at at Bushey Farm in Gettysburg, Pa. Union forces turned away a Confederate advance in the pivotal battle of the Civil War fought July 1-3, 1863, which was also the war's bloodiest conflict with more than 51,000 casualties. (Photo by Matt Rourke/AP Photo)

In this March 22, 1975 file photo, a refugee clutches a baby as a government helicopter gunship carries them away near Tuy Hoa, Vietnam, 235 miles northeast of Saigon. They were among thousands fleeing from Communist advances. AP Photographer Nick Ut will be retiring from the AP in March 2017 after 51 years of taking photographs from the front lines of the Vietnam War to the red carpets of Hollywood. (Photo by Nick Ut/AP Photo)

A three-day-old Bengal tiger calf is cared for after being fed at the National Zoo in Masaya on August 30, 2021. A female Bengal tiger calf was born in the National Zoo of Nicaragua, the fourth of this species in risk of extinction born in captivity in the country, and is under special care due to a limited breastfeeding capacity of the mother. (Photo by Inti Ocon/AFP Photo)

HIV-positive 71-year-old Sylverio Hachiploa (R) talks with caregivers Glandwel Muleya (L) and Sister Abigail Mwaka Mazuba (C) in his thatched hut during a visit by a home-based care team in the village of Nedwmba, south of the Chikuni Mission in the south of Zambia February 23, 2015. The caregivers in the Jesuit-run home-based care project at the Chikuni Mission run a capacity-building and empowerment project at the household level, offering training and assistance in crop-growing and animal rearing, as well as offering companionship, pastoral care and monitoring of the antiretroviral treatment compliance of HIV-AIDS patients. (Photo by Darrin Zammit Lupi/Reuters)

English actress Diana Rigg as “Emma Peel” is tied to a railway track as a miniature train advances on her in a scene from the television series “The Avengers” in 1968. Rigg died at her home in London on 10 September 2020, at the age of 82. (Photo by Popperfoto via Getty Images/Getty Images)

Visitors, wearing face masks, enter the Disneyland theme park in Shanghai as it reopened, Monday, May 11, 2020. Visits will be limited initially and must be booked in advance, and the company said it will increase cleaning and require social distancing in lines for the various attractions. (Photo by Sam McNeil/AP Photo)

One of the most significant challenges related to cancer in Nepal is the lack of awareness around the prognosis of the disease, as many patients, their families and even healthcare professionals consider cancer to be an incurable disease at any stage. This results in significant delays in bringing patients to hospitals, and high rates of advanced stage cancers and mortality. (Photo by Omar Havana)

The Jet Propulsion Lab team's RoboSimian robot turns on a valve at a simulated disaster-response course during day one of the Defense Advanced Research Projects Agency (DARPA) Robotics Challenge finals in Pomona, California, June 5, 2015. (Photo by David McNew/Reuters)