Epidemiologic and Ecologic Investigations of Monkeypox, Likouala Department, Republic of the Congo, 2017

Abstract

Monkeypox, caused by a zoonotic orthopoxvirus, is endemic in Central and West Africa. Monkeypox has been sporadically reported in the Republic of the Congo. During March 22-April 5, 2017, we investigated 43 suspected human monkeypox cases. We interviewed suspected case-patients and collected dried blood strips and vesicular and crust specimens (active lesions), which we tested for orthopoxvirus antibodies by ELISA and monkeypox virus and varicella zoster virus DNA by PCR. An ecologic investigation was conducted around Manfouété, and specimens from 105 small mammals were tested for anti-orthopoxvirus antibodies or DNA. Among the suspected human cases, 22 met the confirmed, probable, and possible case definitions. Only 18 patients had available dried blood strips; 100% were IgG positive, and 88.9% (16/18) were IgM positive. Among animals, only specimens from Cricetomys giant pouched rats showed presence of orthopoxvirus antibodies, adding evidence to this species' involvement in the transmission and maintenance of monkeypox virus in nature.

Keywords: Republic of the Congo; ecology; epidemiology; monkeypox; orthopoxvirus; viruses; zoonoses.

Figure 1

Locations of monkeypox outbreaks and case classifications, Likouala Department, Republic of Congo, 2017. Numbers in circles indicate total number of cases in each area (all case classifications). Inset shows location of study area within Republic of Congo.

Figure 2

Transmission chain: pattern of virus transmission hypothesized to have occurred during monkeypox outbreak in Impfondo, Likouala Department, Republic of Congo, 2017. Case-patients are arranged according to date of symptom onset. Solid lines indicate probable lines of person-to-person transmission and dashed lines depict undetermined (hypothesized) transmission events. The number of days between onsets (case interval) is approximated by length of lines. Case-patients illustrated are siblings belonging to the same household.

Figure 3

Bayesian majority rules consensus tree comparing sequences obtained from Cricetomys specimens collected in Likouala Department, Republic of the Congo, 2017 (boldface), with sequences from Olayemi et al. (31). Vertical black bars distinguish clades representing Cricetomys giant pouched rat species proposed by Olayemi et al. Tree was constructed on the basis of 2 independent runs, 5 million generations each, based on a 409-bp fragment of the cytochrome B gene. Bayesian posterior probabilities for each node are shown. Scale bar indicates nucleotide substitutions per site.