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Poxvirus dilemmas.

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Contraindications↗

Human monkeypox: a study of 2,510 contacts of 214 patients.

A study of 2,510 contacts of 214 patients with human monkeypox was conducted in Zaire from 1980 to 1984. Among the contacts of 130 primary cases of human monkeypox, a further 22 co-primary and 62 secondary cases were detected, and an additional fourteen people who had no evidence of clinical disease had positive serological results. A majority of the clinical and subclinical cases of monkeypox occurred in children less than 10 years of age. Immunity in vaccinated persons now appears to be waning because 16 overt cases occurred in contacts who had been vaccinated. The overall attack rate for contacts without a vaccination scar (7.2%) differed significantly from the attack rate for those who had been vaccinated in the past (0.9%). The attack rate for household contacts was significantly higher than that for other contacts, among both unvaccinated (four times higher) and vaccinated (seven times higher) household contacts. Many unvaccinated contacts living in the same household as the index case under conditions of maximum exposure, however, escaped not only the disease but also infection.

Adolescent↗

Human monkeypox: clinical features of 282 patients.

We present the clinical features and course of 282 patients with human monkeypox in Zaire during 1980-1985. The ages of the patients ranged from one month to 69 years; 90% were less than 15 years of age. The clinical picture was similar to that of the ordinary and modified forms of smallpox. Lymphadenopathy, occurring in the early stage of the illness, was the most important sign differentiating human monkeypox from smallpox and chickenpox. The symptoms, signs, and the course of the disease in patients who had been vaccinated against smallpox differed significantly from those in unvaccinated subjects. Pleomorphism and "cropping" similar to that in chickenpox occurred in 31% of vaccinated and 18% of unvaccinated patients. The prognosis depended largely on the presence of severe complications. No deaths occurred among vaccinated patients. In unvaccinated patients the crude case-fatality rate was 11% but was higher among the youngest children (15%).

Adolescent↗

Four generations of probable person-to-person transmission of human monkeypox.

This paper examines an outbreak of five cases of human monkeypox which occurred in children belonging to two families living in the West Kasai region of Zaire during May-July 1983. Epidemiologic investigations suggest that the first case was infected from an animal source, possibly a monkey, and that each of the other four cases was infected from a previous human case. Three of these cases of presumed person-to-person transmission occurred in close household contacts. The other case infection occurred either by casual contact within the hospital compound, or possibly because of infection due to use of the same syringe for injections. Human monkeypox is the most important orthopoxvirus infection in the post-smallpox eradication period. The disease is a zoonosis and person-to-person transmission is rather difficult. Thus, this episode is a rare event and special analysis of the circumstances is discussed. However, it supports the necessity to carry out surveillance and research on this disease as recently reported by Arita et al.

Animals↗

Re-emergence of monkeypox in Africa: a review of the past six years.

Human monkeypox was first identified in 1970 in the Democratic Republic of the Congo. Extensive studies of this zoonotic infection in the 1970s and 1980s indicated a largely sporadic disease with a minority of cases resulting from person-to-person transmission, rarely beyond two generations. In August 1996, an unusually large outbreak of human monkeypox was reported, and cases continued through 1997 with peak incidence in August 1996, March 1997 and August 1997. Preliminary results from the field investigations in 1997 suggest a new epidemiological pattern where a majority of secondary cases result from person-to-person transmission, and a clinically milder disease. But there is preliminary laboratory evidence of a simultaneous outbreak of varicella in the same geographic region which will undoubtedly modify these preliminary results. Since smallpox was eradicated and vaccinia vaccination terminated in this region, the population of susceptible individuals has grown. The use of vaccination to protect the population at risk, however, must take into account HIV prevalence and the risk of generalized vaccinia when using vaccinia vaccine in populations where HIV is known to be present.

Africa↗

Early epidemiologic and genomic insights from Sierra Leone's first mpox cases, 2025.

INTRODUCTION: early characterization of outbreak cases supports rapid decisions. We conducted real-time analysis during the initial outbreak phase in mid-March 2025 of Sierra Leone's first 44 laboratory-confirmed Mpox cases (10th January to 5th March 2025) to generate epidemiologic and genomic intelligence for response. METHODS: we summarized surveillance data and sequenced 18 early cases with Oxford Nanopore. Firth-penalized logistic regression was employed to explore risk factors for severe disease. RESULTS: median age was 27 years (interquartile range 22 to 35); 68.2% were male. Most cases reported no recent international travel (95.5%). All cases presented with rash; fever occurred in 72.7%. Six cases (13.6%) met severe criteria; no deaths occurred (0 of 44; 95% confidence interval 0 to 8.0). Household secondary attack rate was 7.3% during the study window and 8.2% after completion of follow-up. Sequencing identified two co-circulating sub-lineages consistent with A.2.2 and B.1.6 and a strong APOBEC3 pattern (142 of 212 guanine-to-adenine in thymine-cytosine versus 70 of 212 cytosine-to-thymine in guanine-adenine; exact binomial p approximately 8.6x10-7; X2= 24.5, df = 1, p≈ 7.6x10-7). Root-to-tip analysis showed weak temporal signal (R2=0.31; date randomization p= 0.18), so we did not interpret clock estimates. CONCLUSION: real-time analysis during the initial outbreak phase showed community transmission, quantified household spread, documented two sub-lineages with an APOBEC3 signature, and generated severity hypotheses that immediately informed surveillance and vaccine prioritization. Findings require validation in larger cohorts.

Adult↗

Clinical, epidemiological, and genomic evidence on mpox in mainland China, 2022-2025: a scoping review.

BACKGROUND: Since 2022, mpox has expanded globally with sustained human-to-human transmission and increasing evidence of MPXV genomic diversification. In mainland China, mpox evidence has accumulated rapidly, but clinical, epidemiological, and genomic findings remain fragmented. METHODS: We conducted a scoping review of PubMed, CNKI, and WanFang databases up to March 2, 2026, and integrated literature-derived evidence with public MPXV sequences from GenBank, GenBase, and GISAID. Literature-derived data were used to map clinical-epidemiological characteristics, study-level genomic evidence, sequencing coverage, and reported lineage distribution. Curated public MPXV sequences were used for phylogenetic reconstruction, amino acid mutation profiling, and APOBEC-like substitution analysis. RESULTS: Fifty-eight studies were included: 32 addressed clinical or epidemiological evidence only, 25 addressed genomic evidence only, and one contributed to both domains. Fourteen hospital-based studies summarized 951 cases, showing that reported cases were concentrated among young adult men, with frequent MSM exposure (798/897, 89.0%; 95% CI 86.7-90.9%) and HIV co-infection (469/951, 49.3%; 95% CI 46.1-52.5%). Public sequence curation identified 231 unique mainland China MPXV sequences, of which 230 were used for phylogenetic and mutation analyses. Literature-based genomic evidence comprised 26 genomic studies, 37 study-level genomic records, and 31 reported-case units, including 414 sequenced cases among 530 reported cases (78.1%; 95% CI 74.4-81.4%). Clade IIb predominated among sequenced cases (412/414, 99.5%; 95% CI 98.3-99.9%), with C.1.1 and C.1 most frequently represented. Within the available dataset, public genomes represented multiple lineages and were unevenly distributed across regions and time. Mutation analysis revealed dispersed amino acid variation and a predominance of G>A and C>T transitions (73.0%). After collapsing recurrent substitutions to unique genomic sites, the proportion of G>A/C>T transitions decreased to 35.8% and further to 17.8% under a strict APOBEC3 motif definition, indicating that the observed mutation spectrum includes both shared lineage-associated substitutions and sequence-context-based APOBEC-like patterns. CONCLUSION: Available evidence indicates multi-lineage MPXV circulation and in mainland China, but interpretation remains constrained by uneven sequencing and lack of individual-level clinical-genomic linkage. Integrated genomic surveillance and standardized data linkage are needed to better characterize MPXV transmission and evolution.

APOBEC‑like substitutions↗

Human poxvirus disease after smallpox eradication.

A 5-year-old boy living in a small camp in the rural Ivory Coast had a disease resembling smallpox. This occurred 4 years after smallpox had been eradicated from the Ivory Coast and 1.5 years after the last case of smallpox was detected in West and Central Africa. Clinical, serological, and epidemiological evidence indicated this disease was probably monkeypox, a poxvirus of the variola/vaccina subgroup. A serologic survey of poxvirus antibodies in the wild animal population detected neutralizing antibodies in rodents, larger mammals, primates, and birds. The laboratory and ecological characteristics of poxviruses require further elucidation, especially those which have been found in animals near human monkeypox cases.

Adolescent↗