New study estimates monkeypox incubation, birth times and R0

The first monkeypox infection (MPX) that led to the current global outbreak was identified in Europe in early May 2022. To date, more than 59,000 MPX cases have been reported worldwide.

Stady: Early estimates of monkeypox incubation period, generation time, and breeding number, Italy, May-June 2022. Image Credit: Cryptographer /


Soon after the initial MPX case was identified in Europe, the European Center for Disease Prevention and Control and the World Health Organization (WHO) requested their member states to accurately report both suspected and confirmed MPX cases. Throughout this outbreak, most cases of MPX were diagnosed among men who have sex with men (MSM).

After the initial outbreak reports in Italy, the Italian Ministry of Health recommended several preventive measures to control the spread of the MPX virus. This included implementing quarantine measures, limiting contact and exposure to health care workers, monitoring for symptoms, and contact tracing.

new emerging infectious diseases A periodical study discusses the characteristics of the first 255 confirmed cases of reverse transcription polymerase chain reaction (RT-PCR)-confirmed MPX cases in Italy in 2022.

about studying

The current study included only MPX cases that were confirmed by RT-PCR. In addition to MPX status, the researchers also obtained information about various patient characteristics such as gender, age, presence of rash or other symptoms, first date of symptom onset, travel abroad, and route of exposure.

The incubation period was established for 30 cases with known dates and periods of symptomatic exposure. Generational time was determined using 16 contagious and contagious pairs identified through contact tracing efforts. The net reproduction number was calculated using the generation time.


Only two of the 255 cases of MPX in the current study were identified in men, with 95% of MPX cases identified in MSM. The average age of the study participants was 37 years old.

Of the 184 cases for which additional information was available, 139 reported a rash in the anal or genital area. Moreover, 151 out of 222 cases of fever were recorded.

Of the 228 cases in which travel information was available, 37% reported previous travel abroad. Of these individuals, 25 reported having recently traveled to the Canary Islands, while one had traveled to West Africa.

The mean incubation period was 9.1 days, while the obstetric time was 12.5 days. Furthermore, the net number of copies reached 2.43 during the first week of June and then decreased after June 12, 2022.

The results of the current study provide important information regarding the early stages of the current MPX outbreak in Italy. These notes also explain how long symptoms should be monitored, infected people should be isolated, and contact tracing should be done. In addition, the net reproduction number is also a valid criterion for monitoring the progressive spread of the disease.


The relatively small size of the current study limits the generalizability of these results. Furthermore, selection bias with respect to infection-infectious pairs and recall bias with respect to exposure dates were also evident. An additional limitation of the current study is that “super propagation” events may inflate the observed reproduction number.

Journal reference:

  • Joseta, J, Mamon, A, Ferraro, F, et al. (2022). Early estimates of monkeypox incubation period, generation time, and breeding number, Italy, May-June 2022. emerging infectious diseases. doi: 10.3201/eid2810.221126.