The Zika virus has spread to more than 20 countries, including the U.S., causing the World Health Organization (W.H.O.) on Monday to declare the disease and its suspected link to birth defects an international public health emergency.

From a crisis communications standpoint, the W.H.O’s response demonstrates that the organization has learned some valuable PR lessons from the Ebola outbreak in 2014, when W.H.O also declared a public health emergency but was criticized for being too slow to respond.

Perhaps most the most important takeaway is that when you’re dealing with a potentially epic crisis concerning people’s lives you need use to harness all the institutional and/or corporate muscle you can muster to educate the medical community, the public and the media and try and contain the damage.

The W.H.O has estimated that four million people could be infected with the Zika virus by the end of the year.

International health officials suspect a link between a major Zika outbreak in Brazil and increased reports of a serious birth defect in babies born to infected mothers there. The birth defect, called microcephaly, causes babies to be born with unusually small heads and, in the vast majority of cases, damaged brains, reports said.

At a news conference in Geneva, Dr. Margaret Chan, the director general of the W.H.O, said the emergency designation would allow the health agency to coordinate the many efforts to get desperately needed answers, according to the New York Times.

The Times said that Dr. Chan acknowledged that the understanding of the connection between the Zika virus and microcephaly was hazy and said that the uncertainty placed “a heavy burden” on pregnant women and their families throughout the Americas. An investigation into the connection is underway.

Dr. Chan’s comment on the possible connection between Zika and microcephaly is another important lesson for brand managers and PR pros who are responsible for crisis management: Don’t hesitate to share any information related to how the crisis started—but cannot yet be verified—and will help to communicate how people should deal with the crisis and/or take any preventative measures to mitigate any damage. It also shows that W.H.O. wants to be transparent in its communications.

However, the W.H.O said pregnant women can travel to the affected region. That may cause some blowback, what with Dr. Friedan, director of the Centers for Disease Control and Prevention (CDC) telling Fox News that the “bottom line for people  around the U.S. is, if you’re pregnant don’t go to a place that has a Zika outbreak.”

The onus is on the W.H.O to communicate why it decided not to seek a travel ban among pregnant women to the affected countries. That raises another crucial element of crisis communications.

You can get out in front of the crisis and, through multiple media channels and online platforms, educate your shareholders about the problem and assuage any concerns.

But if one of multiple crisis decisions goes awry and draws the ire among even a few of your stakeholders, the entire exercise may be considered a failure.

Hypervigilance on your decision-making during a crisis—and following those decisions to a logical conclusion—is paramount in PR and marketing communications.