Re-emergence of chikungunya in the Republic of the Congo in 2019 associated with a possible vector-host switch.

In January 2019, an outbreak of chikungunya virus fever was reported in a rural region near Pointe-Noire, Republic of the Congo. Molecular and phylogenetic analysis of this new CHIKV strain demonstrated the presence of the A226V substitution and a surprisingly close relation with Aedes aegypti-associated Central Africa chikungunya strains. These results, combined with the preponderance of Aedes albopictus in the outbreak area, suggest a recent vector-host switch facilitated by the emergence and spread of the A226V mutation from a related CHIKV strain previously circulating in Aedes aegypti. The proximity of this outbreak to the large city of Pointe-Noire alerts us to a possibly devastating future outbreak in the absence of measures limiting the proliferation of Ae. albopictus mosquitoes.

Robustness against serum neutralization of a poliovirus type 1 from a lethal epidemic of poliomyelitis in the Republic of Congo in 2010.

In 2010, a large outbreak of poliomyelitis with unusual 47% lethality occurred in Pointe Noire, Republic of Congo. Vaccine-mediated immunity against the outbreak virus was never investigated. A wild poliovirus 1 (WPV1) isolated from a fatal case (termed PV1-RC2010) showed a previously unknown combination of amino acid exchanges in critical antigenic site 2 (AgS2, VP1 capsid protein positions 221SAAL → 221PADL). These exchanges were also detected in an additional 11 WPV1 strains from fatal cases. PV1-RC2010 escaped neutralization by three different mAbs relevant for AgS2. Virus neutralization was tested in sera from fatal cases, who died before supplementary immunization (n = 24), Gabonese recipients of recent oral polio vaccination (n = 12), routinely vaccinated German medical students (n = 34), and German outpatients tested for antipoliovirus immunity (n = 17) on Vero, human rhabdomyosarcoma, and human epidermoid carcinoma 2 cells. Fatal poliomyelitis cases gave laboratory evidence of previous trivalent vaccination. Neutralizing antibody titers against PV1-RC2010 were significantly lower than those against the vaccine strain Sabin-1, two genetically distinct WPV1s isolated in 1965 and 2010 and two genetically distinct vaccine-derived PV strains. Of German vaccinees tested according to World Health Organization protocols, 15-29% were unprotected according to their neutralization titers (<1:8 serum dilution), even though all were protected against Sabin-1. Phylogenetic analysis of the WPV1 outbreak strains suggested a recent introduction of virus progenitors from Asia with formation of separate Angolan and Congolese lineages. Only the latter carried both critical AgS2 mutations. Antigenetically variant PVs may become relevant during the final phase of poliomyelitis eradication in populations with predominantly vaccine-derived immunity. Sustained vaccination coverage and clinical and environmental surveillance will be necessary.

Novel serotypes 105 and 116 are members of distinct subgroups of human enterovirus C.

The full coding sequences of two novel human enterovirus (HEV)-C serotypes 105 and 116, sampled in the Republic of the Congo in 2010 and in Russia in 2011, were identified in this study. Enterovirus (EV)-105 was closest to EV-104 in the 5' NTR and to EV-109 in the coding genome region. It had the same unconventional 5' NTR as EV-104 and EV-109. The non-cytopathogenic EV-116 was phylogenetically close to coxsackievirus (CV)-A1, CV-A19 and CV-A22, which also cannot be propagated in routinely used cell cultures. There were signs of recombination within this subgroup of HEV-C; however, recombination with conventional HEV-C was restricted, implying partial reproductive isolation. As there is also evidence of different permissive replication systems and distinct genetic properties of these subgroups, they may represent subspecies of the HEV-C species or different stages of speciation.