Children play in a water fountain next to Olympic rings at Madureira Park in Rio de Janeiro in July 2015. (Silvia Izquierdo/AP)

This post has been updated.

More than 100 prominent physicians, bioethicists and scientists from around the world posted a letter Friday urging World Health Organization Director-General Margaret Chan to exert pressure on Olympic authorities to move the Olympics from Rio de Janeiro or delay the Games because of public health concerns over the Zika virus.

Brazil, which is hosting the Olympics and the Paralympics, is at the epicenter of the rapidly evolving mosquito-borne epidemic.

The letter is signed by 150 individuals from more than a dozen countries, including Brazil, Japan, Israel, Russia, Sweden, South Africa and the United States. It calls on the WHO to convene an independent group to advise it and the International Olympic Committee, and for authorities to reconsider the decision to hold the Games in Rio.

"We are doing it to ask for an open, transparent discussion of the risks of holding the Olympics as planned in Brazil," said Arthur Caplan, a bioethicist at New York University and one of the letter's four authors, in an email explaining the reasoning behind the letter.

The group of scientists is not seeking "general assurance" from the WHO, Caplan said. Instead, they want "a frank discussion among independent experts," he said.

"If Rio is going to happen, the world deserves a full discussion of why and at what potential risks and liabilities," Caplan said.


Many of the graves in the Villa Palmeras cemetery in San Juan, Puerto Rico, seen Feb. 22, feature flower urns that hold rainwater, providing the perfect breeding ground for the mosquito that can carry dengue, chikungunya and Zika viruses. (Allison Shelley for The Washington Post)

The other authors are Lee Igel, an associate professor at New York University; Amir Attaran, a biologist and law professor at the University of Ottawa; and Christopher Gaffney, a senior research fellow at the University of Zurich who studies the impact of major sporting events on urban populations.

Each author has published articles in recent weeks and months calling for the Games to be postponed because of Zika.

In the open letter posted Friday on Twitter and Facebook, the authors said evidence shows that Brazil’s Zika strain has more serious medical consequences than researchers previously knew, that Rio de Janeiro is one of the hardest-hit areas of the epidemic, and that Rio’s mosquito-killing efforts are not meeting expectations.

Zika infections during pregnancy can cause serious fetal brain abnormalities, including microcephaly, which is characterized by abnormally small heads and severe developmental problems. The virus has also been linked to neurological disorders in adults. Zika is primarily transmitted through mosquitoes but can also spread through sexual contact.

In the most recent letter, the authors say that Rio’s public health system is so “severely weakened” as to make a last-minute push against the mosquito that transmits Zika impossible. Citing government data, the letter notes the increasing number of cases of dengue, a related virus spread by the same mosquitoes, that is considered a proxy for Zika.

In the specific neighborhood of the Olympic Park, Barra da Tijuca, there have been more dengue cases in the first quarter of 2016 than in all of 2015, the letter said.

“It is therefore imperative that WHO conducts a fresh, evidence-based assessment of Zika and the Games, and its recommendations for travelers,” the letter said. “Given the public health and ethical consequences, not doing so is irresponsible.”

The IOC insists that the Games will go forward as planned. Earlier this month, the WHO urged athletes and travelers planning to attend the competitions to take measures to protect against infection, but it did not call for the Olympics, which start Aug. 5, or the Paralympics, which begin Sept. 7, to be canceled or postponed.

Late Friday, the WHO said that based on its current assessment, "cancelling or changing the location of the 2016 Olympics will not significantly alter the international spread of Zika virus." It noted that Brazil is one of almost 60 countries and territories which have reported continuing spread of Zika by mosquitoes.

"People continue to travel between these countries and territories for a variety of reasons," the statement said. The best way to reduce risk of disease is to follow public health travel advice, the WHO said.

"There is no public health justification for postponing or cancelling the games," the WHO said. U.S. Olympic Committee officials have said the decision to attend the Games is up to individual athletes.

The authors say the estimated 500,000 foreign tourists from all over the world who are expected to attend the Games represent an unnecessary risk because they could potentially get infected and return home to places where the virus can become endemic.

"Should that happen to poor, as-yet unaffected places (e.g., most of South Asia and Africa) the suffering can be great," the authors wrote. "It is unethical to run the risk, just for Games that could proceed anyway, if postponed and/or moved."

U.S. health officials also disagree with the authors' assessment.

In an interview this week, Tom Frieden, the director of the Centers for Disease Control and Prevention, said, “We don’t see from a public health standpoint any reason to cancel the Olympics."

"There’s been some claims that if the Olympics happen, it’s going to disseminate the virus everywhere, it’s going to amplify it," Frieden said. "Well, we looked at the numbers. The Olympics account for less than one quarter of 1 percent of all travel to Zika-affected areas."

Frieden has said the risk to Olympians is "very, very low." About 100 athletes, coaches and staff of the U.S. Olympic delegation are already being monitored for the virus as they begin to go to Brazil; up to 1,000 are expected to be monitored as the Olympics and Paralympics begin.

He said it was "unfortunate" that Major League Baseball recently decided to scrap a two-game series in Puerto Rico and move it to Miami amid concerns over the Zika virus.

CDC and health officials across the globe have advised women who are pregnant to avoid traveling to regions where Zika is prevalent, and they have advised women who are trying to become pregnant, and their male partners, to use condoms or abstain from sex during their stay and for months after returning home.

The CDC is also conducting a risk assessment for each of the approximately 180 countries with athlete delegations. More than 10,500 athletes are expected at the Olympics and about 4,350 are likely to be at the Paralympics. Analysts are looking at the expected number of athletes and travelers likely to go to Brazil, the susceptibility of those countries to epidemic diseases, and the potential for how added travel might accelerate the spread of Zika.

But in Friday's letter, the authors say the many uncertainties about Zika "currently make it impossible for mathematical models to predict the epidemic’s course accurately."

Here's a full list of the 150 people who signed the letter, in alphabetical order, and represent individuals, not their institutions:

1. Professor Akira Akabayashi, Department of Biomedical Ethics, School of Public Health, the University of Tokyo Faculty of Medicine, Tokyo

2. Professor Paul S. Appelbaum, director, Division of Law, Ethics & Psychiatry, Department of Psychiatry, Columbia University, New York

3. Professor Kwame Anthony Appiah, Department of Philosophy, NYU Law, New York University, New York

4. Professor Thalia Arawi, founding director, Salim El-Hoss Bioethics & Professionalism Program, Faculty of Medicine, American University of Beirut, Beirut

5. Professor Amir Attaran, School of Epidemiology, Public Health and Community Medicine and Faculty of Law, University of Ottawa, Canada

6. Stephanie Augustine, researcher, Department of Maternal Fetal Medicine, North Shore University Hospital, Manhasset, N.Y.

7. Professor Robert Baker, Bioethics Program of Clarkson University & the Icahn School of Medicine at Mount Sinai, Schenectady, N.Y.

8. Alison Bateman-House, Division of Medical Ethics, Department of Population Health, New York University School of Medicine, New York

9. Professor Frances Batzer, Department of Obstetrics & Gynecology, Thomas Jefferson University, Philadelphia

10. Professor Angelica M. Baylon, external relations director, Maritime Academy of Asia, Kamaya Point, Philippines

11. Professor Solly Benatar, founding director, University of Cape Town Bioethics Center, Department of Medicine, University of Cape Town, Cape Town, South Africa

12. Professor Cecilia Benoit, Center for Addictions Research of British Columbia, Department of Sociology, University of Victoria, Victoria, Canada

13. Edward J. Bergman, Department of Medical Ethics and Health Policy, Perelman School of Medicine, University of Pennsylvania, Philadelphia

14. Professor Kenneth Berkowitz, Department of Population Health and Department of Medicine, School of Medicine, New York University, New York

15. Professor Ivy Lynn Bourgeault, Canadian Institutes of Health Research chair in gender, work and health human resources, Telfer School of Management, University of Ottawa, Ottawa

16. Professor Marie A. Bragg, Department of Population Health, New York University School of Medicine, New York

17. Berit Bringedal, senior researcher, Institute for Studies of the Medical Profession, Oslo

18. Professor Amy Brown, Maria Fareri Children’s Hospital at Westchester Medical Center, Department of Pediatrics, New York Medical College, Valhalla, N.Y.

19. Professor Arthur L. Caplan, Division of Medical Ethics, New York University Langone Medical Center, New York

20. Rhyddhi Chakraborty, researcher, philosophical bioethics, global public health and social justice, American University of Sovereign Nations, United States.

21. Professor Theeraphap Chareonviriyaphap, Department of Entomology, Kasetsart University, Bangkok

22. Professor Cheryl Cline, Office of Bioethics, Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, Canada.

23. Catherine Constable, instructor, Department of Medicine, New York University Langone Medical Center, New York

24. Professor Glenn Cohen, Petrie-Flom Center for Health Law Policy, Biotechnology & Bioethics, Harvard Law School, Cambridge, Mass.

25. Professor Patrick Derr, chair, Department of Philosophy, Clark University, Worcester, Mass.

26. Professor Débora Diniz, faculty of Law, Universidade de Brasilia, and Bioethics Program, FIOCRUZ, Brasilia and Rio de Janeiro

27. Professor Ames Dhai, director, Steve Biko Center for Bioethics, faculty of Health Sciences, University of the Witwatersrand, Johannesburg

28. Hasan Erbay, MD, PhD, Department of Medical Ethics and History of Medicine, Afyon Kocatepe University Faculty of Medicine, Afyonkarahisar, Turkey

29. Professor Eric Feldman, Health Policy and Medical Ethics, University of Pennsylvania Law School, Philadelphia

30. Holly Fernandez-Lynch, executive director, Petrie-Flom Center for Health Law Policy, Biotechnology and Bioethics, Harvard University, Cambridge, Mass.

31. Professor Chris Feudtner, Department of Pediatrics and Department of Medical Ethics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia

32. Christopher Gaffney, Department of Geography, University of Zurich, Zurich

33. Professor William Gardner, Children’s Hospital of Eastern Ontario Research Institute, faculty of Medicine, University of Ottawa, Ottawa

34. Professor Robert P. George, McCormick professor of jurisprudence, Princeton University, Princeton, N.J.

35. Professor Grover Gilmore, dean, applied social sciences, Case Western Reserve University, Cleveland

36. Professor Moti Gorin, director, Jann Benson Ethics Center, Colorado State University, Fort Collins, Colo.

37. Professor Linda Granowetter, Department of Pediatrics, New York University Langone Medical Center, New York

38. Professor Abhik Gupta, PhD, professor and dean, School of Environmental Sciences, Assam (Central) University, Silchar, India

39. Professor Sally Guttmacher, College of Global Public Health, New York University, New York

40. Professor Negin Hajizadeh, Department of Medicine, Hofstra Northwell School of Medicine, Hofstra University, Hempstead, N.Y.

41. George Halvorson, retired chief executive, Kaiser Permanente, and chair, InterGroup Understanding, Sausalito, Calif.

42. Professor Deborah S. Hamm, Department of Psychiatry, Columbia University Medical Center, New York

43. Professor Alice Herb, Division of Humanities in Medicine at State University of New York, Downstate Medical Center, New York

44. Professor Søren Holm, Center for Social Ethics and Policy, School of Law, University of Manchester, United Kingdom

45. Professor Lee H. Igel, Tisch Institute for Sports Management, Media, and Business, New York University, New York

46. Professor Judy Illes, Canada research chair in neuroethics, Department of Medicine, University of British Columbia, Vancouver, Canada

47. Mahmood-uz- Jahan, MD, PhD, director, Bangladesh Medical Research Council, Dhaka, Bangladesh

48. Professor Dale Jamieson, chair, Department of Environmental Studies, New York University, New York

49. Professor Yeremias Jena, master of philosophy, master of science, professor of medical ethics at Atma Jaya School of Medicine, Atma Jaya Catholic University of Indonesia, Jakarta, Indonesia

50. Professor Steven Joffe, vice chair, Department of Medical Ethics and Health Policy, Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia

51. Professor Ken Johnson, School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, Canada

52. Professor Nora Jones, associate director, Center for Bioethics, Urban Health, and Policy, Lewis Katz School of Medicine, Temple University, Philadelphia

53. Professor Therese Jones, associate director, Center for Bioethics and Humanities, director, Arts and Humanities in Healthcare Program, University of Colorado Anschutz Medical Campus, Denver

54. Professor Matthias A. Karajannis, Division of Pediatric Hematology/Oncology, New York University Langone Medical Center, New York

55. Professor Douglas I. Katz, Department of Neurology, Boston University School of Medicine, Braintree, Mass.

56. Professor Ralph V. Katz, professor of epidemiology, Fellow of the American College of Epidemiology (FACE), and founding chair, Department of Epidemiology and Health Promotion, New York University, New York

57. Lisa Kearns, research associate, Division of Medical Ethics, New York University Langone Medical Center, New York

58. Professor Aaron Seth Kesselheim, Division of Pharmacoepidemiology & Pharmacoeconomics, Brigham and Women’s Hospital, Harvard Medical School, Harvard University, Boston

59. Abbas Kharabi, University of Malaya, Kuala Lumpur, Malaysia

60. Robert Klitzman, professor of psychiatry, director, Masters of Bioethics Program Columbia University, New York

61. Professor Craig Klugman, chair, Department of Health Sciences, DePaul University, Chicago

62. Professor Adam Kolber, Center for Health, Science, and Public Policy, Brooklyn Law School, Brooklyn, New York

63. Professor Craig Konnoth, senior fellow, Leonard Davis Institute of Health Economics, University of Pennsylvania Law School, Philadelphia

64. Professor Ralph A. Korpman, School of Medicine, Loma Linda University School of Medicine, Loma Linda, Calif.

65. Ronald L. Krall, Center for Bioethics and Health Law, University of Pittsburgh, Pittsburgh

66. Professor Sheldon Krimsky, Department of Urban and Environmental Policy & Planning, Department of Health and Community Medicine, Tufts University, Boston

67. Professor John Lantos, director of pediatric bioethics, Department of Pediatrics, University of Missouri at Kansas City School of Medicine, Kansas City, Mo.

68. Professor John Last, School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, Ottawa

69. Professor Stephen Latham, director, Interdisciplinary Center for Bioethics, Yale University, New Haven, Conn.

70. Thuy Le, Oxford University Clinical Research Unit, Oxford University, Ho Chi Minh City, Vietnam

71. Professor Arthur Leader, Department of Obstetrics and Gynecology, Faculty of Medicine, University of Ottawa, Ottawa

72. Leonard leBlanc, research fellow, Eubios Ethics Institute, Japan

73. Professor Trudo Lemmens, Scholl Chair in Health Law and Policy, Faculty of Law, University of Toronto, Toronto

74. Professor Betty Wolder Levin, School of Public Health and Health Policy, City University of New York, New York

75. Professor Bruce Levin, Department of Biostatistics, Mailman School of Public Health, Columbia University, New York

76. Professor Ariane Lewis, Department of Neurology and Department of Neurosurgery, New York University Langone Medical Center, New York

77. Ana Lita, director, Global Bioethics Initiative, New York

78. Professor Julian Little, director, School of Epidemiology, Public Health and Preventive Medicine, Faculty of Medicine, University of Ottawa, Ottawa

79. Professor Sergio Litewka, Institute for Bioethics and Health Policy, Miller School of Medicine, University of Miami, Miami

80. Professor Alex John London, director, Center for Ethics and Policy, Carnegie Mellon University, Pittsburgh

81. Darryl Macer, PhD, honorary degree, president, American University of Sovereign Nations, Arizona; director, Eubios Ethics Institute, Christchurch, New Zealand

82. Professor Tim Mackey, director, Global Health Policy Institute, Department of Anesthesiology and Public Health, University of California at San Diego, San Diego

83. Professor Ruth Macklin, Department of Epidemiology & Population Health, Albert Einstein College of Medicine, Yeshiva University, New York

84. Professor Cheryl Macpherson, Bioethics Department, St George’s University School of Medicine, True Blue, Grenada

85. Professor Brian Martin, director, graduate program in public health, Eastern Virginia Medical School, Old Dominion University, Norfolk, Va.

86. Professor Thomas Mayo, Southern Methodist University Dedman School of Law, University of Texas Southwestern Medical School, Dallas

87. Michael Mawadri, emergency coordinator with Action for Development (AFOD) in South Sudan

88. Professor James McCartney (Reverend, Order of St. Augustine), Department of Philosophy, Villanova University, Villanova, Penn.

89. Professor John Merz, Department of Medical Ethics & Health Policy, Perelman School of Medicine at the University of Pennsylvania, Philadelphia

90. Alan Milstein, sports attorney, Sherman, Silverstein, Kohl, Rose & Podolsky, Moorestown, N.J.

91. Professor Christine Mitchell, executive director, Center for Bioethics, Harvard Medical School, Boston

92. Professor Jonathan D. Moreno, Department of Medical Ethics and Health Policy, Perelman School of Medicine, University of Pennsylvania, Philadelphia

93. Professor Martin Müller, Department of Geography, University of Zurich, Zurich

94. Professor Carin Muhr, Department of Medical Science, Uppsala University, Uppsala, Sweden.

95. Professor Anna Nolan, Department of Environmental Medicine , Department of Medicine, New York University Langone Medical Center, New York

96. Professor Stjepan Oreskovic, Andrija Stampar School of Public Health, University of Zagreb School of Medicine, Zagreb, Croatia

97. Professor Brendan Parent, Division of Medical Ethics, and co-director, NYU Sports and Society Program, New York University, New York

98. Professor Shamina Parvin Lasker, head of Department of Anatomy, Samorita Medical College; secretary general, Bangladesh Bioethics Society, Dhaka, Bangladesh

99. Professor Pasquale Patrizio, Division of Reproductive Endocrinology & Infertility, Yale School of Medicine, New Haven, Conn.

100. Professor Sean Philpott-Jones, Department of Bioethics, Clarkson University, Schenectady, N.Y.

101. Carolyn Plunkett, Division of Medical Ethics, New York University Langone Medical Center, New York

102. Professor Stephen G. Post, Department of Family, Population & Preventive Medicine, Stony Brook University School of Medicine, Stony Brook, N.Y.

103. Professor Kathleen Powderly, director, John Conley Division of Medical Ethics and Humanities, SUNY Downstate Medical Center, Brooklyn, N.Y.

104. Professor Duncan Purves, Environmental Studies and Bioethics, New York University, New York

105. Professor Vojin Rakic, founding director, Center for the Study of Bioethics, Head of the European Division of the UNESCO Chair in Bioethics, University of Belgrade, Serbia

106. Professor Vardit Ravitsky, School of Public Health, Université de Montréal, Montreal

107. Professor Avad Raz, Department of Sociology and Anthropology, Ben-Gurion University of the Negev, Be’er-Sheva, Israel

108. Professor Kathleen Reeves, eirector, Center for Bioethics, Urban Health, and Policy, Lewis Katz School of Medicine, Temple University, Philadelphia

109. Professor Donald R. Roberts, Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, Bethesda, Md.

110. Philip Rubin, retired principal assistant director, Office of Science and Technology Policy (OSTP), Executive Office of the President of the United States, New Haven, Conn.

111. Professor William Ruddick, founding director, Center for Bioethics, New York University, New York

112. Professor Maya Sabatello, Department of Psychiatry, Columbia University, New York

113. Mojgan Saleuhipour, faculty of Biomedicine, South Baylo University, Calif.

114. Professor Judit Sandor, director of the Center for Ethics and Law in Biomedicine, Central European University, Budapest

115. Professor Pamela L. Sankar, Department of Medical Ethics and Health Policy, Perelman School of Medicine, University of Pennsylvania, Philadelphia

116. Professor Arthur Schaefer, founding director, Center for Professional and Applied Ethics, University of Manitoba, Canada

117. Professor Udo Schuklenk, Ontario Research Chair in Bioethics, Department of Philosophy, Queen’s University, Kingston, Canada

118. Professor Evan Selinger, Department of Philosophy, Rochester Institute of Technology, Rochester, N.Y.

119. M. Selvanayagam, professor, dean of research and president of India Association of Bioethics, India

120. Professor Seema K. Shah, Department of Pediatrics, University of Washington School of Medicine, Seattle

121. Professor William S. Silvers, University of Colorado Denver School of Medicine, Denver

122. Professor Peter Singer, University Center for Human Values, Princeton University, Princeton, N.J.; and School of Historical and Philosophical Studies, University of Melbourne, Melbourne, Australia

123. Professor Maria Fiatarone Singh, chair of exercise and sport science, Faculty of Health Sciences, Sydney Medical School, University of Sydney, Australia

124. Professor Daniel Skinner, assistant professor of Health Policy, Department of Social Medicine, Ohio University, Dublin, Ohio

125. Raquel R. Smith, PhD, professor of clinical psychology, American University of Sovereign Nations, Arizona; FEMA Community Emergency Response Team instructor and manager

126. Professor Robert Smith, Department of Mathematics and Faculty of Medicine, University of Ottawa, Ottawa

127. Professor Jeremy Snyder, faculty of Health Science, Simon Fraser University, Burnaby, Canada

128. Professor Robert W. Snyder, Esq., attorney at law, professor of health-care management and finance, American University of Sovereign Nations School of Medicine, Arizona

129. Professor Martin Strosberg, Bioethics Program of Clarkson University & the Icahn School of Medicine at Mount Sinai, Schenectady, N.Y.

130. Professor Eileen Sullivan-Marx, dean, School of Nursing, New York University, New York

131. Professor Edwin van Teijlingen, Center for Midwifery, Maternal & Perinatal Health, Faculty of Health & Social Sciences, Bournemouth University, Bournemouth, U.K.

132. Professor Henk ten Have, director, Center for Healthcare Ethics, Duquesne University, Pittsburgh

133. Ananya Tritipthumrongchok, general manager, International Peace and Development Ethics Center, Kaeng Krachan, Thailand

134. Professor Duunjian Tsai, MD, PhD, professor, Taipei Medical University, Taiwan

135. Professor Connie Ulrich, Department of Biobehavioral Health Sciences, University of Pennsylvania School of Nursing, Philadelphia

136. Professor Erick Valdés, Universisad del Desarrollo, Chile

137. Professor Robert M. Veatch, Kennedy Institute of Ethics, Georgetown University, Washington, D.C.

138. Professor J. David Velleman, professor of philosophy and bioethics, New York University, New York

139. Ford Vox, Brain Injury Medicine, Shepherd Center, Atlanta

140. Gary I. Wadler, past chairman, World Anti-Doping Agency (WADA) Prohibited List Committee, recipient of the International Olympic Committee’s President’s Prize in 1993, Manhasset, N.Y.

141. Wendell Wallach, lecturer, Yale Interdisciplinary Center for Bioethics, New Haven, Conn.

142. Professor Vivian Welch, School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, Ottawa

143. Professor Bruce Wilcox, faculty of Public Health, Mahidol University, Bangkok

144. Professor Benjamin Wilfond, director, Treuman Katz Center for Pediatric Bioethics, Seattle Children’s Research Institute, Department of Pediatrics, University of Washington, Seattle

145. Professor Loren Wissner Greene, Department of Population Health and Bioethics, Department of Obstetrics and Gynecology, New York University Langone Medical Center, New York

146. Professor Wendy L. Wobeser, Division of Infectious Diseases, Queen’s University, Kingston, Canada

147. Professor Paul Root Wolpe, Asa Griggs Candler Professor of Bioethics, and director, Center for Ethics, Emory University, Atlanta

148. Professor Sanni Yaya, School of International Development and Global Studies, Faculty of Social Sciences, University of Ottawa, Ottawa

149. Professor Boris Yudin, Department of Humanitarian Expertise and Bioethics, Institute of Philosophy, Russian Academy of Sciences, Moscow

150. Diana Zuckerman, president, National Center for Health Research, Washington, D.C.

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