Acute hemorrhagic conjunctivitis epidemic in Colon, Republic of Panama

Dynamic modelling of strategies for the control of acute haemorrhagic conjunctivitis outbreaks in schools in Changsha, China (2004–2015)

Outbreaks of acute haemorrhagic conjunctivitis (AHC) – a rapidly progressing and highly contagious infection – often occur in schools during summer and autumn. We used dynamic modelling to evaluate the efficacy of interventions to control AHC outbreaks in schools. A susceptible-infected-recovered (SIR) model was built to simulate AHC outbreaks in Chinese schools, with isolation or school closure added into the model. We used outbreak data from the period 2004–2015 in our models to estimate the effective reproduction number and assess the efficacy of interventions. The median effective reproduction number (uncontrolled) of AHC outbreaks was 7·00 (range 1·77–25·87). The median effective reproduction number (controlled) of AHC outbreaks was 0·16 (range 0·00–2·28). Intervention efficacy is affected by the timing of isolation; earlier isolation is associated with a lower morbidity peak and smaller total attack rate (TAR). School closures were not effective; TARs were almost 100% and did not change even when different school closure durations were adopted. Isolation and school closure as a combined intervention strategy was used to simulate outbreak control, but the efficacy was the same as isolation alone. An isolation programme could be an effective primary intervention during AHC outbreaks in schools. However, school closure is not recommended.

A modeling and experiment framework for the emergency management in AHC transmission

Emergency management is crucial to finding effective ways to minimize or even eliminate the damage of emergent events, but there still exists no quantified method to study the events by computation. Statistical algorithms, such as susceptible-infected-recovered (SIR) models on epidemic transmission, ignore many details, thus always influencing the spread of emergent events. In this paper, we first propose an agent-based modeling and experiment framework to model the real world with the emergent events. The model of the real world is called artificial society, which is composed of agent model, agent activity model, and environment model, and it employs finite state automata (FSA) as its modeling paradigm. An artificial campus, on which a series of experiments are done to analyze the key factors of the acute hemorrhagic conjunctivitis (AHC) transmission, is then constructed to illustrate how our method works on the emergency management. Intervention measures and optional configurations (such as the isolation period) of them for the emergency management are also given through the evaluations in these experiments.

Expression of enterovirus 70 capsid protein VP1 in Escherichia coli

The VP1 gene of enterovirus 70 (EV70) possesses a large number of Escherichia coli low-usage codons (11.0%) and a bacterial ribosome binding site complementary sequence (RBSCS) 5'-UGUCUCCUUUUC-3' flanking the codon 139. Plasmids containing EV70 cDNA encoding the full-length VP1 failed to express in E. coli (BL21(DE3), Rosetta 2(DE3) or Rosetta (DE3)pLysS). High expression (>8% of total protein) of recombinant VP1 (rVP1m) in E. coli required engineering of the encoding cDNA (conserved modification of the native cDNA) by simultaneous substitution of a rare-codon cluster located between codons 103 and 132, and replacement of the RBSCS-TCCTTT sequence. The rare-codon frequencies of the cDNAs encoding VP1 non-overlapping terminal fragments N138 (1-138 aa) and C170 (141-310 aa) are similar (10.9 and 11.2%, respectively). However, in E. coli, high expression of recombinant C170 (rC170) required no modification of the native cDNA whereas high expression of recombinant N138 (rN138m) required minimal synonymous substitution of the above rare-codon cluster. The rare-codon cluster of EV70 VP1 gene has five least-usage arginine codons (AGG/AGA) and three tandem rare-codon pairs (AGGAGG, CUAAGG, and AGACUA). Our results suggest that the rare-codon cluster (its rare codon arrangement per se and/or its related mRNA secondary structure(s)) and the RBSCS in EV70 VP1 gene, not the rare-codon frequency, constitute the key elements that suppress its expression in E. coli.

Systemic and ocular antibody responses to inactivated acute hemorrhagic conjunctivitis (AHC) virus; enterovirus 70 (EV70)

PURPOSE

Evaluate the immune response in rabbits injected with EV70, the agent of acute hemorrhagic conjunctivitis (AHC) and AHC associated neuropathy.

METHODS

Rabbits were injected intramuscularly with uv-light inactivated EV70 isolate J670/71. Neutralizing activity against EV70 was quantified in serum and tear samples and the immunoglobulin (Ig) classes of the neutralizing activity in serum identified by sucrose gradient ultra-centrifugation. Adjuvant muramyl dipeptide (MDP) was applied topically to assess the role of ocular inflammation on levels of neutralizing antibody, proteins and Ig in tears. The protective effects of human and rabbit sera and interferon-alpha (IFN-alpha) against EV70 were compared in human conjunctival and lens cells.

RESULTS

Sera collected at 6 and 13 d contained 19S IgM anti-EV70 neutralizing antibody, while serum collected 21 d post injection contained 19S IgM and 7S IgG anti-EV70 neutralizing antibody. Low titers of anti-EV70 activity (< or =30 U/ml) were detected in tears of seropositive rabbits. MDP induction of conjunctivitis in seropositive rabbits increased tear IgG concentration (3-fold) and anti-EV70 neutralizing antibody titers (> or =10-fold). The protective effect of the rabbit and human sera against EV70 infection in conjunctival, but not lens epithelial cells, was enhanced by the addition of IFN-alpha.

CONCLUSIONS

Immunization with uv-light inactivated EV70 elicits a classical humoral immune response in rabbits. The protective activity of serum in EV70-infected human conjunctival cells, but not lens cells, was increased by IFN-alpha. Adjuvant MDP-induced conjunctivitis, increased blood-conjunctival barrier (BCB) permeability and anti-EV70 neutralizing activity in tear of seropositive rabbits. The results suggest immunization with inactivated EV70 could provide systemic as well as ocular protection during natural EV70 infection.

Community-wide outbreak of enteroviral illness caused by echovirus 30: a cross-sectional survey and a case-control study

BACKGROUND

In June, 1997, 21 children from a single community in Germany were hospitalized with aseptic meningitis. An epidemiologic investigation was conducted to determine the extent of the outbreak and risk factors for illness.

METHOD

The extent of the outbreak was assessed with a cross-sectional survey of every 10th child listed in the town register among the 2240 town children < 16 years old. A case-control study determined risk factors for illness. Sixty-two cases were identified through the cross-sectional survey from hospitalized persons and from persons seen by local physicians. Controls were 114 asymptomatic persons identified from the cross-sectional survey.

RESULTS

The overall attack rate was 16%, with the highest attack rates (24%) among the 6- to 8-year olds. Onsets occurred during a 37-day period. Among the 2240 town children <16 years of age, an estimated 353 met the case definition for enteroviral illness, 168 visited a doctor and 21 were hospitalized. Data from the case-control study indicated that contact with an ill household member [odds ratio (OR) = 6.3; 95% confidence interval (CI) 2.6 to 15.5], day-care attendance (OR = 2.6; 95% CI 1.1 to 6.2) and playground use, either two to three times per week (OR = 3.7; 95% CI 1.3 to 10.2) or daily (OR = 4.3; 95% CI 1.6 to 11.3), were risk factors for illness.

CONCLUSION

Echovirus 30 caused substantial morbidity during this community outbreak caused by person-to-person spread. Household contacts, day-care centers and playgrounds were prominent risk factors for transmission.

Enterovírus-70 na região metropolitana de São Paulo, Brasil, de 1984 a 1987: aspectos da infecção em períodos epidêmico e endêmico

São apresentados os resultados de estudos sobre o comportamento do Enterovírus-70 (EV-70) na região metropolitana de São Paulo desde sua provável introdução no verão de 1984, determinando extensa epidemia de conjuntivite hemorrágica aguda (C.H.A.), até o final de 1987 abrangendo período em que este agravo foi pouco notado. Na fase epidêmica ocorrida no primeiro trimestre de 1984 foram estudados 291 indivíduos divididos em três grupos denominados A, B e C, o primeiro formado por pessoas atingidas pela C.H.A. e os outros dois por indivíduos não atingidos por este agravo mas que, respectivamente, referiam contato domiciliar com casos de C.H.A. e os que não referiam o citado contato. A demonstração de anticorpos se fez pela técnica de imunofluorescência indireta (IFI) para detectar IgM específico para EV-70 e pela prova de neutralização em cultura de células BHK-21. Verificou-se que 56,7%, 33,3% e 20,6% dos indivíduos pertencentes, respectivamente, aos grupos A, B e C apresentavam anticorpos específicos da classe IgM. No grupo A a faixa etária mais atingida foi a de 10 a 29 anos. No período que vai do fim da primeira e única epidemia até o final de 1987, identificaram-se três casos esporádicos de C.H.A. e 10 pacientes com afecção neurológica aguda associada à infecção recente pelo EV-70. Nove, destes 10 casos, apresentaram paralisia de nervos cranianos, todos evoluindo sem seqüelas clinicamente discerníveis. As formas assintomáticas e os casos esporádicos de C.H.A. e de afecções neurológicas mantiveram a circulação do EV-70 no período não epidêmico.

Spread of acute hemorrhagic conjunctivitis due to enterovirus-70: effect of air temperature and relative humidity on virus survival on fomites

Enterovirus 70 (EV-70) has caused at least two pandemics and several major epidemics of acute hemorrhagic conjunctivitis (AHC) in the past 18 years, with the largest number of cases occurring in the coastal areas of the tropics. The exact means of its spread are not known, but fomites and hands contaminated by them are the most likely vehicles. We, therefore, tested EV-70 survival under different environmental conditions using stainless steel disks (1 cm diameter). Each disk received 10 microliter of the virus in phosphate-buffered saline (PBS). The disks were held at various temperatures with the relative humidity (RH) at the low (20 +/- 5%), medium (50 +/- 5%), high (80 +/- 5%), or ultrahigh (95 +/- 5%) level. The virus was eluted from the disks with tryptose phosphate broth and the eluate assayed in LLC-MK2cells. Inactivation rates (Ki), expressed as hourly loss of virus plaque forming units (PFU) in log10, were then calculated. At 20 degrees C, virus survival was proportional to the RH level, with the highest virus survival at the ultrahigh RH; at this level nearly 5% of the input virus was detectable even after 24 hr. Virus inactivation rates were only slightly higher at the ultrahigh RH when the temperature was raised to 33 degrees C or 35 degrees C. However, at 80% RH, increasing the temperature from 20 degrees C to 33 degrees C resulted in a dramatic rise in virus inactivation. The finding that high levels of RH prolong EV-70 survival on fomites may help explain the epidemiology of AHC resulting from EV-70.