Dr. Matthew Hsieh, Dr. John Tisdale and Lynndrick Holmes discuss Holmes' recovery from sickle cell anemia after participating in Tisdale's clinical trial at the National Institute of Health's Clinical Center in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

Dr. Matthew Hsieh, Dr. John Tisdale and Lynndrick Holmes discuss Holmes' recovery from sickle cell anemia after participating in Tisdale's clinical trial at the National Institute of Health's Clinical Center in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

Lynndrick Holmes, 29, walks with Dr. John Tisdale through the National Institute of Health's Clinical Center after the agency announced a breakthrough in sickle cell anemia research in Bethesda, U.S. March 11, 2019. Holmes has shown significant recovery from the disease after participating in Tisdale's clinical trial. REUTERS/Erin Scott 

Lynndrick Holmes, 29, walks with Dr. John Tisdale through the National Institute of Health's Clinical Center after the agency announced a breakthrough in sickle cell anemia research in Bethesda, U.S. March 11, 2019. Holmes has shown significant recovery from the disease after participating in Tisdale's clinical trial. REUTERS/Erin Scott 

Lynndrick Holmes, 29, discusses his recovery from sickle cell anemia after participating in Dr. John Tisdale's clinical trial at the National Institute of Health's Clinical Center in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

Lynndrick Holmes, 29, discusses his recovery from sickle cell anemia after participating in Dr. John Tisdale's clinical trial at the National Institute of Health's Clinical Center in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

Lynndrick Holmes, 29, discusses his recovery from sickle cell anemia after participating in Dr. John Tisdale's clinical trial at the National Institute of Health's Clinical Center in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

A researcher works in Dr. John Tisdale's lab at the National Institutes of Health after the agency announced a breakthrough in sickle cell anemia research in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

Dr. John Tisdale speaks with a researcher in his lab at the National Institutes of Health after the agency announced a breakthrough in sickle cell anemia research in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

Dr. John Tisdale speaks with one of his a lab assistants at the National Institutes of Health after the agency announced a breakthrough in sickle cell anemia research in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

Dr. John Tisdale discusses his work for the National Institute of Health's breakthrough in sickle cell anemia research during an interview in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

Dr. John Tisdale discusses his work for the National Institute of Health's breakthrough in sickle cell anemia research during an interview in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

Dr. John Tisdale discusses his work for the National Institute of Health's breakthrough in sickle cell anemia research during an interview in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

National Institutes of Health Director Francis Collins discusses his agency's breakthrough in sickle cell anemia research during an interview in Washington, U.S. March 11, 2019. REUTERS/Erin Scott 

National Institutes of Health Director Francis Collins discusses his agency's breakthrough in sickle cell anemia research during an interview in Washington, U.S. March 11, 2019. REUTERS/Erin Scott 

National Institutes of Health Director Francis Collins poses for a portrait after his agency announced a breakthrough in sickle cell anemia research in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

National Institutes of Health Director Francis Collins poses for a portrait after his agency announced a breakthrough in sickle cell anemia research in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

National Institutes of Health Director Francis Collins poses for a portrait after his agency announced a breakthrough in sickle cell anemia research in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

National Institutes of Health Director Francis Collins poses for a portrait after his agency announced a breakthrough in sickle cell anemia research in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

National Institutes of Health Director Francis Collins discusses his agency's breakthrough in sickle cell anemia research during an interview in Bethesda, U.S. March 11, 2019. REUTERS/Erin Scott 

Advocate Children's Hospital staff members Katelyn Anderson (L), Ann Marie Anzalone (2nd L) and Kevynne Chawle (R) help Sophia Trujillo with a nebulizer treatment at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo gets a nebulizer treatment at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo has blood drawn from the mediport in her chest at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo has her temperature taken while nurse Ann Marie Anzalone helps her with her boots at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo (L) prepares to have blood drawn during her regular treatment at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo plays a game with Katelyn Anderson while getting a nebulizer treatment at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Irish, Spanish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo adjusts her headband as she has her mediport checked while waiting to check in at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo (L) is examined by Dr. Caitlin Agrawal (C) as she plays a game with Kevynne Chawle at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo has blood drawn from her mediport at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young TPX IMAGES OF THE DAY

Sophia Trujillo covers her eyes while playing a game with nurses during a nebulizer treatment at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo plays with her doll while waiting for treatment at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015.Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo (L) has her mediport cleaned before having blood drawn for her regular treatment at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo (L) prepares to have blood drawn during treatment at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo is measured by Vicky Hernandez during her admittance check at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo prepares to have blood drawn from a mediport in her chest at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo (L) has blood drawn from a mediport in her chest as Katelyn Anderson (C) and Kevynne Chawle look on at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo speaks to Dr. Caitlin Agrawal during her treatment at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo (R) "high-fives" Katelyn Anderson while playing a game during a visit at Advocate Children's Hospital for regular treatment in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

Sophia Trujillo prepares to have blood drawn from her mediport in her chest at Advocate Children's Hospital in Park Ridge, Illinois, September 25, 2015. Trujillo has aplastic anemia and needs a bone marrow transplant but with her multi-racial background of Filipino, Spanish, Irish and Italian, the search for her match has been difficult. REUTERS/Jim Young

A telerobotic pitching machine controlled remotely by thirteen-year-old Nick LeGrande from around 1,800 miles (2896 km) away in Kansas City, Missouri prepares to deliver the ceremonial first pitch before an MLB American League baseball game between Oakland Athletics and New York Yankees at O.co Coliseum in Oakland, California June 12, 2013. LeGrande, who can no longer attend games due to severe aplastic anemia, a rare blood disorder, will use the same technology used by remote operations aboard the International Space Station to deliver the first robotic pitch in the history of Major League Baseball from a specially-constructed mini-baseball stadium build by Google. REUTERS/Stephen Lam (UNITED STATES - Tags: SPORT BASEBALL SCIENCE TECHNOLOGY) 

A nurse assists a man donating blood at a blood drive of the German red cross (DRK) in Berlin, June 6, 2011. German hospitals are struggling to cope with the flood of E.coli victims, as scientists remain puzzled by the deadly bug that has killed 22 and sickened 2,200 people across Europe. Hospitals in the northern port city of Hamburg, the epicentre of the outbreak that began three weeks ago,have been moving out patients with less serious illnesses to handle the surge of people stricken by the rare and virulent bacteria. REUTERS/Fabrizio Bensch (GERMANYPOLITICS - Tags: HEALTH) POLITICS) 

The scene of treatment of an Afghan boy supposedly suffering anemia is reflected in a visor of U.S. Army crew chief SFC Vinle Farrell from "Dustoff" team, C Company, 1-214 Aviation Regiment, 101st Combat Aviation Brigade aboard a medevac helicopter in Helmand province, Afghanistan, April 9, 2011. REUTERS/Denis Sinyakov (AFGHANISTAN - Tags: MILITARY HEALTH) 

U.S. Army crew chief SFC Vinle Farrell (L) and medic SGT Darrell Mckinstry from "Dustoff" team, C Company, 1-214 Aviation Regiment, 101st Combat Aviation Brigade try to keep alive an Afghan boy supposedly suffering anemia aboard a medevac helicopter on their way to a hospital in Camp Dwyer in Helmand province, Afghanistan, April 9, 2011. REUTERS/Denis Sinyakov (AFGHANISTAN - Tags: MILITARY HEALTH) 

U.S. Army medic SGT Darrell Mckinstry (R) from "Dustoff" team, C Company, 1-214 Aviation Regiment, 101st Combat Aviation Brigade tries to keep alive an Afghan boy supposedly suffering anemia as his father and crew chief SFC Vinle Farrell watch them aboard a medevac helicopter on their way to a hospital in Camp Dwyer in Helmand province, Afghanistan, April 9, 2011. REUTERS/Denis Sinyakov (AFGHANISTAN - Tags: MILITARY HEALTH) 

U.S. Army medic SGT Darrell Mckinstry (L) from "Dustoff" team, C Company, 1-214 Aviation Regiment, 101st Combat Aviation Brigade leads colleagues as they carry an Afghan boy supposedly suffering anemia to a medevac helicopter at Camp Bastion in Helmand province, Afghanistan, April 9, 2011. REUTERS/Denis Sinyakov (AFGHANISTAN - Tags: MILITARY HEALTH) 

U.S. Army crew chief SFC Vinle Farrell (L) and medic SGT Darrell Mckinstry from "Dustoff" team, C Company, 1-214 Aviation Regiment, 101st Combat Aviation Brigade try to keep alive an Afghan boy supposedly suffering anemia aboard a medevac helicopter on their way to a hospital in Camp Dwyer in Helmand province, Afghanistan, April 9, 2011. REUTERS/Denis Sinyakov (AFGHANISTAN - Tags: MILITARY HEALTH) 

Ducati MotoGP rider Casey Stoner of Australia powers his bike during the second free practice for the German Grand Prix at the Sachsenring circuit, near the eastern German town of Hohenstein-Ernsthal, July 18, 2009. Stoner is suffering from mild anemia and gastritis but will race in Germany this weekend, the 2007 champion's Ducati team said on Tuesday. REUTERS/Thomas Peter (GERMANY SPORT MOTOR RACING IMAGES OF THE DAY) 

Ducati MotoGP rider Casey Stoner of Australia talks after the second free practice for the German Grand Prix at the Sachsenring circuit, near the eastern German town of Hohenstein-Ernsthal, July 18, 2009. Stoner is suffering from mild anemia and gastritis but will race in Germany this weekend, the 2007 champion's Ducati team said on Tuesday. REUTERS/Thomas Peter (GERMANY SPORT MOTOR RACING) 

Ducati MotoGP rider Casey Stoner of Australia talks after the second free practice for the German Grand Prix at the Sachsenring circuit, near the eastern German town of Hohenstein-Ernsthal, July 18, 2009. Stoner is suffering from mild anemia and gastritis but will race in Germany this weekend, the 2007 champion's Ducati team said on Tuesday. REUTERS/Thomas Peter (GERMANY SPORT MOTOR RACING) 

Ducati MotoGP rider Casey Stoner of Australia powers his bike during the second free practice for the German Grand Prix at the Sachsenring circuit, near the eastern German town of Hohenstein-Ernsthal, July 18, 2009. Stoner is suffering from mild anemia and gastritis but will race in Germany this weekend, the 2007 champion's Ducati team said on Tuesday. REUTERS/Thomas Peter (GERMANY SPORT MOTOR RACING IMAGES OF THE DAY) 

A farmer passes in front of the company Acuinova Chile, located in Puerto Chacabuco, which lies 1,625 km (1,010 miles) south of the capital Santiago February 28, 2009. A deadly fish virus and scarce credit have clobbered the salmon sector in Chile, the world's No. 2 producer, and the industry has shed 6,000 jobs since the infectious salmon anemia (ISA) emerged in 2007. Picture taken February 28, 2009. To match feature CHILE-SALMON/CRISIS REUTERS/Victor Ruiz Caballero (CHILE HEALTH BUSINESS ENVIRONMENT) 

Salmon carcasses are put into a bin filled with ice in a plant at Acuinova Chile, located in Puerto Chacabuco, which lies 1,625 km (1,010 miles) south of the capital Santiago February 28, 2009. A deadly fish virus and scarce credit have clobbered the salmon sector in Chile, the world's No. 2 producer, and the industry has shed 6,000 jobs since the infectious salmon anemia (ISA) emerged in 2007. Picture taken February 28, 2009. To match feature CHILE-SALMON/CRISIS REUTERS/Victor Ruiz Caballero (CHILE HEALTH BUSINESS ENVIRONMENT) 

Workers process farmed salmon in a plant at Acuinova Chile, located in Puerto Chacabuco, which lies 1,625 km (1,010 miles) south of the capital Santiago February 28, 2009. A deadly fish virus and scarce credit have clobbered the salmon sector in Chile, the world's No. 2 producer, and the industry has shed 6,000 jobs since the infectious salmon anemia (ISA) emerged in 2007. Picture taken February 28, 2009. To match feature CHILE-SALMON/CRISIS REUTERS/Victor Ruiz Caballero (CHILE HEALTH BUSINESS ENVIRONMENT) 

Salmon carcasses are seen in the line of work in a plant at Acuinova Chile, located in Puerto Chacabuco, which lies 1,625 km (1,010 miles) south of the capital Santiago February 28, 2009. A deadly fish virus and scarce credit have clobbered the salmon sector in Chile, the world's No. 2 producer, and the industry has shed 6,000 jobs since the infectious salmon anemia (ISA) emerged in 2007. Picture taken February 28, 2009. To match feature CHILE-SALMON/CRISIS REUTERS/Victor Ruiz Caballero (CHILE HEALTH BUSINESS ENVIRONMENT) 

Workers process farmed salmon in a plant at Acuinova Chile, located in Puerto Chacabuco, which lies 1,625 km (1,010 miles) south of the capital Santiago February 28, 2009. A deadly fish virus and scarce credit have clobbered the salmon sector in Chile, the world's No. 2 producer, and the industry has shed 6,000 jobs since the infectious salmon anemia (ISA) emerged in 2007. Picture taken February 28, 2009. To match feature CHILE-SALMON/CRISIS REUTERS/Victor Ruiz Caballero (CHILE HEALTH BUSINESS ENVIRONMENT) 

Workers process farmed salmon in a plant at Acuinova Chile, located in Puerto Chacabuco, which lies 1,625 km (1,010 miles) south of the capital Santiago February 28, 2009. A deadly fish virus and scarce credit have clobbered the salmon sector in Chile, the world's No. 2 producer, and the industry has shed 6,000 jobs since the infectious salmon anemia (ISA) emerged in 2007. Picture taken February 28, 2009. To match feature CHILE-SALMON/CRISIS REUTERS/Victor Ruiz Caballero (CHILE HEALTH BUSINESS ENVIRONMENT) 

Workers put pieces of salmon into a box to be sent to the world market at Acuinova Chile's plant located in Puerto Chacabuco, which lies 1,625 km (1,010 miles) south of the capital Santiago February 28, 2009. A deadly fish virus and scarce credit have clobbered the salmon sector in Chile, the world's No. 2 producer, and the industry has shed 6,000 jobs since the infectious salmon anemia (ISA) emerged in 2007. Picture taken February 28, 2009. To match feature CHILE-SALMON/CRISIS REUTERS/Victor Ruiz Caballero (CHILE ENVIRONMENT HEALTH BUSINESS) 

A cook at the Urkupina restaurant pours broth on a slab of bull's testicle as she serves the popular "caldo de cardan" soup, made of bull's penis and testicles, in El Alto on the outskirts of La Paz February 2, 2009. The soup, considered to be an energy booster and sought after by people suffering from anemia, hangovers and sexual impotency, costs less than $2 per dish and is generally sold in restaurants located near the slaughterhouses of Bolivian cities. Picture taken February 2. REUTERS/David Mercado (BOLIVIA) 

A cook at the Urkupina restaurant holds up a bull's penis and testicles, key ingredients in the popular "caldo de cardan" soup, in El Alto on the outskirts of La Paz February 2, 2009. The soup, considered to be an energy booster and sought after by people suffering from anemia, hangovers and sexual impotency, costs less than $2 per dish and is generally sold in restaurants located near the slaughterhouses in Bolivian cities. Picture taken February 2. REUTERS/David Mercado (BOLIVIA) 

A waiter at the Urkupina restaurant opens for business to sell the popular dish "caldo de cardan", made from boiled bull's penis and testicles, in El Alto on the outskirts of La Paz February 2, 2009. The soup, considered to be an energy booster and sought after by people suffering from anemia, hangovers and sexual impotency, costs less than $2 per dish and is generally sold in restaurants located near the slaughterhouses in Bolivian cities. Picture taken February 2. REUTERS/David Mercado (BOLIVIA)