Assessment of Risk Factors Associated with Diphtheria Outbreaks in Different Areas of Pakistan, September-November 2022: A Case Control Study

Vaccine preventable diseases
Respiratory Diseases

Background: Diphtheria caused by Corynebacterium diphtheriae is re-emerging as a public health issue in low-middle income countries. During 2022, Diphtheria outbreaks were reported from different areas of Pakistan. A case-control study was conducted using data of cases confirmed in Public Health Laboratories at NIH-Pakistan. The objective was to assess risk factors associated with cases and recommendations for control.

Methods: A case-control study was conducted. Case defined as “any person whose sample was positive for isolation of Corynebacterium spp. and for its toxin production, with toxigenicity confirmed by the phenotypic Elek test at NIH between September to November 2022.” For each case, two age, sex and area matched control were taken. Data collected on pre-tested questionnaire. Frequencies, and attack rates calculated. Risk factors analyzed by computing odds ratios at 95%CI and p-value <0.05.

Results: Total 21 cases were confirmed from different areas of KP, Balochistan, Punjab and Sindh. Mean age was 8.5 years (SD: +5), and male-to-female ratio was 1.3:1. The overall attack rate was 01/million, CFR was 4.7%, while most affected age group was 6-10 years with an attack rate of 3/million. Most affected area was district Killa Saifullah in Balochistan with an attack rate of 3/million. Among cases, 17(81%) presented with febrile condition while 16(76%) had pseudo membrane and 20(95%) recovered. Total 12(57%) cases were un-vaccinated. Sharing of utensils (OR:16.9, CI: 3.2-88.7), contact with case (OR:7.0, CI: 1.2-40), illiteracy of parents (OR:4.7, CI: 1.5-15.1), and un-vaccinated status (OR:3.5, CI: 1.2-10.2) were significantly associated with the disease.

Conclusions: This study revealed that children were mostly affected. Sharing utensils, contact with patient and illiteracy of parents were probable risk factors associated with the disease. It is recommended to sensitize the masses regarding the protective effect of vaccination on diphtheria transmission. DPT booster doses to children in the later stage of childhood are recommended.