Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), reiterated on Friday that cutting off flights from China early on during what has become a worldwide pandemic was key to slowing the spread of the Chinese coronavirus in the United States.

President Donald Trump restricted entry to the United States from China beginning January 31 and imposed bans on individuals who had traveled from a third country, but recently visited or transited through China. The pandemic began in central Wuhan, a major Chinese transport hub, in mid-November, but the Communist Party did not reveal the existence of the outbreak until January, silencing doctors and others spreading health information online.

As the pandemic expanded, Trump also imposed restrictions of flights from Europe and recently limited travel across the north and southern American borders.

The World Health Organization (WHO), following Trump’s initial move to ground flights from China, urged countries not to close their borders to foreigners traveling from China, out of concern it would harm Chinese trade.

Referring to the ban on Chinese flights at the White House press conference on Friday, Dr. Fauci, the United States’ top infectious disease expert, said, “The two pillars, the two elements of our capability to contain the infection and the surge of infections in this country rely on two things: keeping infections from coming from without in. We’ve been very successful in doing that with China and with Europe.”

Fauci had endorsed the policy the day before. In an interview Thursday with NBC News, Dr. Fauci said cutting off air travel from China was “right” and has “gone a long way” in slowing the spread of the Chinese coronavirus in the United States:

[O]ne of the things we did right was very early cut off travel from China to the United States. Because outside of China, where it originated, the countries in the world that have it are through travel, either directly from China or indirectly from someone who went someplace and then came to that particular country. Our shutting off travel from China and, more recently, travel from Europe, has gone a long way to not seeding very, very intensively the virus in our country.

A recent CNN report said that, in conversations behind closed doors, Fauci has also suggested grounding domestic flights to help contain the spread of the virus.

The WHO has consistently rejected the proposal that limiting travel can contain an outbreak. Last year, as the Ebola outbreak in Democratic Republic of Congo (DRC) expanded across the Rwandan and Ugandan borders, the WHO “strongly advise[d] against the closure of borders or implementation of any restrictions on travel and trade,” arguing that “such measures push the movement of people and goods to informal border crossings that are not monitored, thus increasing the chances of the spread of disease.” Unlike coronaviruses, the Ebola virus, named after the eponymous African river, spreads through contact with blood and bodily fluids of an infected person and is not believed to be airborne or especially contagious.

The WHO has repeatedly offered similar advice during the current pandemic. On February 3 – nearly two weeks after the Chinese Communist Party made the existence of the novel coronavirus public on January 20 – WHO chief Tedros Adhanom Ghebreyesus referred to cutting off flights from China as extreme, telling the WHO Executive Board at a meeting in Geneva, “There is no reason for measures that unnecessarily interfere with international travel and trade.”

Last week, WHO official Dr. Bruce Aylward similarly discouraged restrictions on travel.

“What we found, as a general principle – not a general principle, a pretty robust principle – is that it doesn’t help to restrict movement,” Aylward advised. “What you’re really interested in is: Where is the virus? The viruses in the cases, the viruses in their close contacts.”