Epidemic hysteria following the National School Deworming Day, Zamboanga Peninsula, Philippines, 2015


  • Johnette Agpoon Peñas Department of Health, Philippines
  • Vikki Carr de los Reyes Department of Health, Philippines
  • Ma. Nemia Sucaldito Department of Health, Philippines
  • Julius Erving Ballera Department of Health, Philippines
  • Herdie Hizon Department of Health, Philippines
  • Rio Magpantay Department of Health, Philippines
  • Vicente Belizario Jr Department of Health, Philippines
  • Kenneth Hartigan-Go Department of Health, Philippines




Introduction: In July 2015, the Philippines conducted a school-based mass drug administration using albendazole for soil-transmitted helminths infection. Reports of adverse events were subsequently made through the event-based surveillance system, mostly from the Zamboanga Peninsula on the island of Mindanao. A team from the Epidemiology Bureau investigated the reports of adverse events following mass drug administration (AEFMDA).

Methods: Five schools were identified for the investigation which comprised an unmatched case-control study, key informant interviews and laboratory examinations. AEFMDA cases were students who had sudden onset of abdominal pain, vomiting, diarrhoea, loss of consciousness, headache or dizziness within 24 hours after intake of deworming tablet; controls were healthy students who did not develop signs and symptoms after deworming.

Results: Most (85%) of the 7313 AEFMDA cases reported nationwide were from Zamboanga Peninsula. Most reports were made after rumours of deaths following deworming and of the use of expired drug were spread through the region. Many parents sent their children to hospital, even if asymptomatic. The case-control study found that being an AEFMDA case was associated with no history of previous deworming (odds ratio = 4.08, 95% confidence interval: 1.77–9.42).

Discussion: The investigation concluded that epidemic hysteria was the cause of the increased number of AEFMDA cases in the Zamboanga Peninsula. The false information, aggravated by social media, caused panic and an increase in reporting. Some cases had no history of deworming, and they may not have been aware that albendazole is safe and that side-effects are expected. Risk communication before, during and after future national deworming programmes are recommended to prevent unnecessary reporting of AEFMDA.

Author Biography

Johnette Agpoon Peñas, Department of Health, Philippines

Field Epidemiology Training Program Fellow, 

Epidemiology Bureau, Department of Health, Philippines


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How to Cite

Peñas, J. A., de los Reyes, V. C., Sucaldito, M. N., Ballera, J. E., Hizon, H., Magpantay, R., Belizario Jr, V., & Hartigan-Go, K. (2018). Epidemic hysteria following the National School Deworming Day, Zamboanga Peninsula, Philippines, 2015. Western Pacific Surveillance and Response, 9(4). https://doi.org/10.5365/wpsar.2017.8.1.009



Field Investigation Report