Hantavirus in humans: a review of clinical aspects and management

Hantavirus infections are part of the broad group of viral haemorrhagic fevers. They are also recognised as a distinct model of an emergent zoonotic infection with a global distribution. Many factors influence their epidemiology and transmission, such as climate, environment, social development, ecology of rodent hosts, and human behaviour in endemic regions. Transmission to humans occurs by exposure to infected rodents in endemic areas; however, Andes hantavirus is unique in that it can be transmitted from person to person. As hantaviruses target endothelial cells, they can affect diverse organ systems; increased vascular permeability is central to pathogenesis. The main clinical syndromes associated with hantaviruses are haemorrhagic fever with renal syndrome (HFRS), which is endemic in Europe and Asia, and hantavirus cardiopulmonary syndrome (HCPS), which is endemic in the Americas. HCPS and HFRS are separate clinical entities, but they share several features and have many overlapping symptoms, signs, and pathogenic alterations. For HCPS in particular, clinical outcomes are highly associated with early clinical suspicion, access to rapid diagnostic testing or algorithms for presumptive diagnosis, and prompt transfer to a facility with critical care units. No specific effective antiviral treatment is available.

First wave of SARS-CoV-2 in Santiago Chile: Seroprevalence, asymptomatic infection and infection fatality rate

BACKGROUND

The first wave of SARS-CoV-2 infection in Chile occurred during the cold season reaching a peak by the end of June 2020, with 80 % of the cases concentrated in its capital, Santiago. The main objective of this study was to estimate the attack rate during this first wave of SARS-CoV-2 in a large, densely populated city with more than seven million inhabitants. Since the number of confirmed cases provides biased information due to individuals' potential self-selection, mostly related to asymptomatic patients and testing access, we measured antibodies against SARS-CoV-2 to assess infection prevalence during the first wave in the city, as well as estimate asymptomatic cases, and infection fatality ratio. To our knowledge this is one of the few population-based cross-sectional serosurvey during the first wave in a highly affected emerging country. The challenges of pandemic response in urban settings in a capital city like Santiago, with heterogeneous subpopulations and high mobility through public transportation, highlight the necessity of more accurate information regarding the first waves of new emerging diseases.

METHODS

From April 24 to June 21, 2020, 1326 individuals were sampled from a long-standing panel of household representatives of Santiago. Immunochromatographic assays were used to detect IgM and IgG antibody isotypes.

RESULTS

Seroprevalence reached 6.79 % (95 %CI 5.58 %-8.26 %) in the first 107 days of the pandemic, without significant differences among sex and age groups; this figure indicates an attack rate 2.8 times higher than the one calculated with registered cases. It also changes the fatality rate estimates, from a 2.33 % case fatality rate reported by MOH to an estimated crude 1.00 % (CI95 % 0.97-1.03) infection fatality rate (adjusted for test performance 1.66 % [CI95 % 1.61-1.71]). Most seropositive were symptomatic (81,1 %).

CONCLUSIONS

Despite the high number of cases registered, mortality rates, and the stress produced over the health system, the vast majority of the people remained susceptible to potential new epidemic waves. We contribute to the understanding of the initial spread of emerging epidemic threats. Consequently, our results provide better information to design early strategies that counterattack new health challenges in urban contexts.

Proteinuria in Hantavirus Cardiopulmonary Syndrome: A Frequent Finding Linked To Mortality

OBJECTIVES

To determine the relative frequency and prognosis value of proteinuria in hantavirus cardiopulmonary syndrome (HCPS) due to Andes virus.

METHODS

This observational analytical study prospectively obtained data from patients admitted to 12 health centers in nine Chilean cities between 2001 and 2018. Only patients with confirmed Andes virus HCPS and laboratory characterization that included qualitative proteinuria determination at admission were considered.

RESULTS

The database involved 175 patients, 95 of them had a measurement of urine protein at the time of hospital admission. They were mainly male (71%) and the median age was 35 [22-47] years. Median duration of the febrile prodromal time was 5 [4-7] days. Hospital length of stay and hospital mortality rate were 10 [7-14] days and 21.1%, respectively. Seventy-three patients (77%) were identified with proteinuria at admission, which was associated with increased mortality rate (26% versus 5%, p=0.036) and the relative risk was 1.3 [1.1-1.6], p=0.002.

CONCLUSIONS

Proteinuria is a frequent finding in patients with HCPS, which is associated with a higher mortality rate.

Targeted high volume hemofiltration could avoid extracorporeal membrane oxygenation in some patients with severe Hantavirus cardiopulmonary syndrome

Background

Hantavirus cardiopulmonary syndrome (HCPS) has a high lethality. Severe cases may be rescued by venoarterial extracorporeal membrane oxygenation (VA ECMO), alongside substantial complications. High volume hemofiltration (HVHF) is a depurative technique that provides homeostatic balance allowing hemodynamic stabilization in some critically ill patients.

Methods

We implemented HVHF before VA ECMO consideration in the last five severe HCPS patients requiring mechanical ventilation and vasoactive drugs admitted to our intensive care unit. Patients were considered HVHF‐responders if VA ECMO was avoided and HVHF‐nonresponders if VA ECMO support was needed despite HVHF. A targeted‐HVHF strategy compounded by aggressive hyperoncotic albumin, sodium bicarbonate, and calcium supplementation plus ultrafiltration to avoid fluid overload was implemented on three patients.

Results

Patients had maximum serum lactate of 8.8 (8.7–12.8) mmol/L and a lowest cardiac index of 1.8 (1.8–1.9) L/min/m². The first two required VA ECMO. They were connected later to HVHF, displayed progressive tachycardia and declining stroke volume. The opposite was true for HVHF‐responders who received targeted‐HVHF. All patients survived, but one of the VA ECMO patients suffered a vascular complication.

Conclusion

HVHF may contribute to support severe HCPS patients avoiding the need for VA ECMO in some. Early connection and targeted‐HVHF may increase the chance of success.

Comparison of VSV Pseudovirus and Focus Reduction Neutralization Assays for Measurement of Anti-Andes orthohantavirus Neutralizing Antibodies in Patient Samples

Andes orthohantavirus (ANDV) is the etiologic agent of hantavirus cardiopulmonary syndrome (HCPS), which has a case fatality rate around 35%, with no effective treatment or vaccine available. ANDV neutralizing antibody (NAb) measurements are important for the evaluation of the immune response following infection, vaccination, or passive administration of investigational monoclonal or polyclonal antibodies. The standard assay for NAb measurement is a focus reduction neutralization test (FRNT) featuring live ANDV and must be completed under biosafety level (BSL)-3 conditions. In this study, we compared neutralization assays featuring infectious ANDV or vesicular stomatitis virus (VSV) pseudovirions decorated with ANDV glycoproteins for their ability to measure anti-ANDV NAbs from patient samples. Our studies demonstrate that VSV pseudovirions effectively measure NAb from clinical samples and have greater sensitivity compared to FRNT with live ANDV. Importantly, the pseudovirus assay requires less labor and sample materials and can be conducted at BSL-2.

Hemodynamic and Pulmonary Permeability Characterization of Hantavirus Cardiopulmonary Syndrome by Transpulmonary Thermodilution

Hantavirus cardiopulmonary syndrome (HCPS) is characterized by capillary leak, pulmonary edema (PE), and shock, which leads to death in up to 40% of patients. Treatment is supportive, including mechanical ventilation (MV) and extracorporeal membrane oxygenation (ECMO). Hemodynamic monitoring is critical to titrate therapy and to decide ECMO support. Transpulmonary thermodilution (TPTD) provides hemodynamic and PE data that have not been systematically used to understand HCPS pathophysiology. We identified 11 HCPS patients monitored with TPTD: eight on MV, three required ECMO. We analyzed 133 measurements to describe the hemodynamic pattern and its association with PE. The main findings were reduced stroke volume, global ejection fraction (GEF), and preload parameters associated with increased extravascular lung water and pulmonary vascular permeability compatible with hypovolemia, myocardial dysfunction, and increased permeability PE. Lung water correlated positively with heart rate (HR, r = 0.20) and negatively with mean arterial pressure (r = −0.27) and GEF (r = −0.36), suggesting that PE is linked to hemodynamic impairment. Pulmonary vascular permeability correlated positively with HR (r = 0.31) and negatively with cardiac index (r = −0.49), end-diastolic volume (r = −0.48), and GEF (r = −0.40), suggesting that capillary leak contributes to hypovolemia and systolic dysfunction. In conclusion, TPTD data suggest that in HCPS patients, increased permeability leads to PE, hypovolemia, and circulatory impairment.

A 19 Year Analysis of Small Mammals Associated with Human Hantavirus Cases in Chile

Small mammals present in areas where hantavirus cardiopulmonary syndrome (HCPS) cases had occurred in central and southern Chile were captured and analyzed to evaluate the abundance of rodents and seroprevalence rates of antibodies to Andes orthohantavirus (ANDV). Sampling areas ranged from the Coquimbo to Aysén regions (30–45° S approx.) regions. Ninety-two sites in peridomestic and countryside areas were evaluated in 19 years of sampling. An antibody against ANDV was detected by strip immunoassay in 58 of 1847 specimens captured using Sherman traps. Of the eleven species of rodents sampled, Abrothrix olivacea, Oligoryzomys longicaudatus and Abrothrix hirta were the most frequently trapped. O. longicaudatus had the highest seropositivity rate, and by logistic regression analysis, O. longicaudatus of at least 60 g had 80% or higher probability to be seropositive. Sex, age and wounds were significantly related to seropositivity only for O. longicaudatus. Across administrative regions, the highest seropositivity was found in the El Maule region (34.8–36.2° S), and the highest number of HCPS cases was registered in the Aysén region. Our results highlight the importance of long term and geographically extended studies, particularly for highly fluctuating pathogens and their reservoirs, to understand the implications of the dynamics and transmission of zoonotic diseases in human populations.

Platelet Count in Patients with Mild Disease at Admission is Associated with Progression to Severe Hantavirus Cardiopulmonary Syndrome

Background: Hantavirus cardiopulmonary syndrome (HCPS) has a mortality up to 35–40% and its treatment is mainly supportive. A variable to predict progression from mild to severe disease is unavailable. This study was performed in patients with documented infection by Andes orthohantavirus, and the aim was to find a simple variable to predict progression to moderate/severe HCPS in patients with mild disease at admission. Methods: We performed a retrospective analysis of 175 patients between 2001 and 2018. Patients were categorized into mild, moderate, and severe disease according to organ failure and advanced support need at hospital admission (e.g., mechanical ventilation, vasopressors). Progression to moderate/severe disease was defined accordingly. Clinical and laboratory variables associated with progression were explored. Results: Forty patients with mild disease were identified; 14 of them progressed to moderate/severe disease. Only platelet count was different between those who progressed versus those that did not (37 (34–58) vs. 83 (64–177) K/mm³, p < 0.001). A ROC curve analysis showed an AUC = 0.889 (0.78–1.0) p < 0.001, with a platelet count greater than 115K /mm³ ruling out progression to moderate/severe disease. Conclusions: In patients with mild disease at presentation, platelet count could help to define priority of evacuation to tertiary care centers.

Molecular method for the detection of Andes hantavirus infection: validation for clinical diagnostics

Hantavirus cardiopulmonary syndrome is a severe disease caused by exposure to New World hantaviruses. Early diagnosis is difficult due to the lack of specific initial symptoms. Antihantavirus antibodies are usually negative until late in the febrile prodrome or the beginning of cardiopulmonary phase, while Andes hantavirus (ANDV) RNA genome can be detected before symptoms onset. We analyzed the effectiveness of quantitative reverse transcription polymerase chain reaction (RT-qPCR) as a diagnostic tool detecting ANDV-Sout genome in peripheral blood cells from 78 confirmed hantavirus patients and 166 negative controls. Our results indicate that RT-qPCR had a low detection limit (~10 copies), with a specificity of 100% and a sensitivity of 94.9%. This suggests the potential for establishing RT-qPCR as the assay of choice for early diagnosis, promoting early effective care of patients, and improving other important aspects of ANDV infection management, such as compliance of biosafety recommendations for health personnel in order to avoid nosocomial transmission.

Person-to-person household and nosocomial transmission of andes hantavirus, Southern Chile, 2011

Four persons became ill after exposure to a patient infected with the virus; 2 cases involved hospital transmission.

Andes hantavirus (ANDV) causes hantavirus cardiopulmonary syndrome in Chile and is the only hantavirus for which person-to-person transmission has been proven. We describe an outbreak of 5 human cases of ANDV infection in which symptoms developed in 2 household contacts and 2 health care workers after exposure to the index case-patient. Results of an epidemiologic investigation and sequence analysis of the virus isolates support person-to-person transmission of ANDV for the 4 secondary case-patients, including nosocomial transmission for the 2 health care workers. Health care personnel who have direct contact with ANDV case-patients or their body fluids should take precautions to prevent transmission of the virus. In addition, because the incubation period of ANDV after environmental exposure is longer than that for person-to-person exposure, all persons exposed to a confirmed ANDV case-patient or with possible environmental exposure to the virus should be monitored for 42 days for clinical symptoms.

High-dose intravenous methylprednisolone for hantavirus cardiopulmonary syndrome in Chile: a double-blind, randomized controlled clinical trial

BACKGROUND

Andes virus (ANDV)-related hantavirus cardiopulmonary syndrome (HCPS) has a 35% case fatality rate in Chile and no specific treatment. In an immunomodulatory approach, we evaluated the efficacy of intravenous methylprednisolone for HCPS treatment, through a parallel-group, placebo-controlled clinical trial.

METHODS

Patients aged >2 years, with confirmed or suspected HCPS in cardiopulmonary stage, admitted to any of 13 study sites in Chile, were randomized by study center in blocks of 4 with a 1:1 allocation and assigned through sequentially numbered envelopes to receive placebo or methylprednisolone 16 mg/kg/day (≤1000 mg) for 3 days. All personnel remained blinded except the local pharmacist. Infection was confirmed by immunoglobulin M antibodies or ANDV RNA in blood. The composite primary endpoint was death, partial pressure of arterial oxygen/fraction of inspired oxygen ratio ≤55, cardiac index ≤2.2, or ventricular tachycardia or fibrillation within 28 days. Safety endpoints included the number of serious adverse events (SAEs) and quantification of viral RNA in blood. Analysis was by intention to treat.

RESULTS

Infection was confirmed in 60 of 66 (91%) enrollees. Fifteen of 30 placebo-treated patients and 11 of 30 methylprednisolone-treated patients progressed to the primary endpoint (P = .43). We observed no significant difference in mortality between treatment groups (P = .41). There was a trend toward more severe disease in placebo recipients at entry. More subjects in the placebo group experienced SAEs (P = .02). There were no SAEs clearly related to methylprednisolone administration, and methylprednisolone did not increase viral load.

CONCLUSIONS

Although methylprednisolone appears to be safe, it did not provide significant clinical benefit to patients. Our results do not support the use of methylprednisolone for HCPS.

CLINICAL TRIALS REGISTRATION

NCT00128180.

Indirect immunofluorescence assay for the simultaneous detection of antibodies against clinically important old and new world hantaviruses

In order to detect serum antibodies against clinically important Old and New World hantaviruses simultaneously, multiparametric indirect immunofluorescence assays (IFAs) based on biochip mosaics were developed. Each of the mosaic substrates consisted of cells infected with one of the virus types Hantaan (HTNV), Puumala (PUUV), Seoul (SEOV), Saaremaa (SAAV), Dobrava (DOBV), Sin Nombre (SNV) or Andes (ANDV). For assay evaluation, serum IgG and IgM antibodies were analyzed using 184 laboratory-confirmed hantavirus-positive sera collected at six diagnostic centers from patients actively or previously infected with the following hantavirus serotypes: PUUV (Finland, n=97); SEOV (China, n=5); DOBV (Romania, n=7); SNV (Canada, n=23); ANDV (Argentina and Chile, n=52). The control panel comprised 89 sera from healthy blood donors. According to the reference tests, all 184 patient samples were seropositive for hantavirus-specific IgG (n=177; 96%) and/or IgM (n=131; 72%), while all control samples were tested negative. In the multiparametric IFA applied in this study, 183 (99%) of the patient sera were IgG and 131 (71%) IgM positive (accordance with the reference tests: IgG, 96%; IgM, 93%). Overall IFA sensitivity for combined IgG and IgM analysis amounted to 100% for all serotypes, except for SNV (96%). Of the 89 control sera, 2 (2%) showed IgG reactivity against the HTNV substrate, but not against any other hantavirus. Due to the high cross-reactivity of hantaviral nucleocapsid proteins, endpoint titrations were conducted, allowing serotype determination in >90% of PUUV- and ANDV-infected patients. Thus, multiparametric IFA enables highly sensitive and specific serological diagnosis of hantavirus infections and can be used to differentiate PUUV and ANDV infection from infections with Murinae-borne hantaviruses (e.g. DOBV and SEOV).

Pandemic influenza A (H1N1) 2009 with neurological manifestations, a case series

Please cite this paper as: Noriega et al. (2010) Pandemic influenza a (H1N1) 2009 with neurological manifestations, a case series. Influenza and Other Respiratory Viruses 4(3), 117–120.

Objectives  Describe a series of atypical presentations of pandemic influenza A (H1N1) 2009.

Methods  Description of case series using hospital records.

Results  Six patients aged 1 to 65 years with confirmed pandemic influenza A (H1N1) 2009 infection presented with neurological complications within 2 to 5 days after the first signs of influenza‐like illness. All six were admitted with seizures or altered mental status. No abnormalities were found in brain scans or cerebral spinal fluid studies of any of the six. All were discharged without sequelae within days of admission.

Conclusions  This is only the second report of pandemic influenza presenting with neurological manifestations. Clinicians caring for patients when pandemic influenza is prevalent in their communities should maintain a high level of awareness of the potential atypical presentations with which this disease can appear.

Diagnosis and treatment of new world hantavirus infections

PURPOSE OF REVIEW

The purpose of this review is to summarize the current knowledge regarding the diagnosis and treatment of indigenous new world hantavirus infections.

RECENT FINDINGS

Recent studies have defined the incubation period of new world hantavirus infections, provided additional evidence for person-to-person transmission of Andes virus, described a rapid method for the presumptive diagnosis of infection in the cardiopulmonary phase through a review of the peripheral smear, and suggested that intravenous ribavirin is probably not effective for the treatment of new world hantavirus infections when started in the cardiopulmonary phase.

SUMMARY

Presumptive diagnosis may be made by a review of the peripheral blood smear after the onset of the cardiopulmonary phase. Critical care management includes the avoidance of fluid overload, pressors to maintain cardiac output, and the use of extracorporeal membrane oxygenation in the most severe cases, but treatment with intravenous ribavirin is probably not effective.

Incubation period of hantavirus cardiopulmonary syndrome

The potential incubation period from exposure to onset of symptoms was 7–39 days (median 18 days) in 20 patients with a defined period of exposure to Andes virus in a high-risk area. This period was 14–32 days (median 18 days) in 11 patients with exposure for <48 hours.

Serological assays for the detection of human andes hantavirus infections based on its yeast-expressed nucleocapsid protein

BACKGROUND

The objective of the study was to develop and evaluate IgM and IgG ELISAs and an IgG Western blot test for the serological detection of human infections with Andes virus (ANDV), the major cause of hantavirus cardiopulmonary syndrome (HCPS) in South America.

METHODS

The entire nucleocapsid (N) protein-encoding sequence of ANDV (strain AH-1) was cloned and expressed in the yeast Saccharomyces cerevisiae. The polyhistidine-tagged recombinant N (rN) protein of ANDV was purified by nickel-chelation chromatography and characterized by its reactivity with different N-specific monoclonal antibodies. To detect an antibody response directed against ANDV in humans, indirect IgM and IgG ELISAs and an IgG Western blot test based on ANDV rN antigen were developed. The evaluation of the tests was performed using a negative serum panel and 63 blinded sera from Argentina and Chile, containing acute-phase and convalescent sera from HCPS patients.

RESULTS

The specificities and sensitivities for the IgM and IgG ELISAs were demonstrated to be very high. The IgG ELISA data were confirmed by the IgG Western blot assay based on the same rN antigen. Almost all anti-ANDV-positive sera reacted to higher endpoint titers with N protein of ANDV than with those of Sin Nombre, Laguna Negra or Puumala virus. The cross-reactivity of anti-ANDV-N IgG-positive sera to rN proteins of other hantaviruses was found to be increased with time after the onset of HCPS.

CONCLUSION

The high sensitivity of the novel assays should facilitate early diagnosis of ANDV infections and might contribute to a successful treatment of HCPS patients.

[Presence of Bartonella henselae in cats: natural reservoir quantification and human exposition risk of this zoonoses in Chile]

BACKGROUND

The availability of a serologic test for cat scratch disease in humans has allowed the diagnosis of an increasing number of cases of this disease in Chile.

AIM

To perform a serological survey for Bartonella henselae among cats in Chile.

MATERIAL AND METHODS

Blood samples from 187 cats living in three Chilean cities were obtained. IgG antibodies against Bartonella henselae were measured using indirect immunofluorescence. Blood cultures were done in 60 samples. The presence of Bartonella henselae in positive cultures was confirmed by restriction fragment length polymorphism polymerase chain reaction (RFLP-PCR).

RESULTS

The general prevalence of IgG antibodies against Bartonella henselae was 85.6%. No differences in this prevalence were found among cats younger or older than 1 year, or those infested or not infested with fleas. However domestic cats had a lower prevalence when compared with stray cats (73 and 90% respectively, p <0.01). Bartonella henselae was isolated in 41% of blood cultures. All the isolated were confirmed as Bartonella henselae by RFLP-PCR.

CONCLUSIONS

This study found an important reservoir of Bartonella henselae in Chilean cats and therefore a high risk of exposure in humans who have contact with them.

Peridomestic small mammals associated with confirmed cases of human hantavirus disease in southcentral Chile

Cases of human hantavirus disease have been reported in Chile since 1995, most of them in people living in rural and periurban areas. We conducted a peridomestic study of small mammals to evaluate the relationships between the presence of rodents with antibodies to Andes virus confirmed human cases of hantavirus pulmonary syndrome in southcentral Chile. The results of 20 sampled sites, which involved the capture of 272 mice over an 18-month period, showed the occurrence of 10 small mammal species, of which Oligoryzomys longicaudatus was the only seropositive species for hantavirus, with an intra-specific serologic rate of 10.4%.

Age-specific prevalence of antibodies to hepatitis A in Santiago, Chile: risk factors and shift in age of infection among children and young adults

Transition from high to lower endemicity of hepatitis A virus (HAV) infection may portend increased public health burden with the shift of infection to older ages and increasing morbidity and mortality. This report describes age-specific prevalence of antibodies to HAV (anti-HAV) among children and young adults in Santiago, Chile, compared with previous prevalence data and assesses factors predictive for anti-HAV. In 1998, a serosurvey was performed in Metropolitan Santiago, designed to enroll a representative, age-stratified population on the basis of area of residence. A total of 784 individuals (age range, 1-24 years) were enrolled. Anti-HAV prevalence by year of life was as follows: ages 1 to 4, 12.5%; 5 to 9, 26.2%; 10 to 14, 43.4%; 15 to 19, 57.4%; 20 to 24, 73.9%. Adjusting for age, factors associated (inversely) with anti-HAV included residential areas of higher socioeconomic status (SES), parental education, and household characteristics of potable water, municipal sewage system, and the presence of a toilet or refrigerator in the house. In logistic regression analysis, only maternal years of education and residence in areas of higher SES remained independently associated with anti-HAV. Excluding those from higher SES areas, comparison of the age-specific anti-HAV prevalence data from previous studies of similar methodology in areas of lower SES revealed consistent decreases across all age groups; the age-standardized prevalence for this age range (1-24 years) dropped from 53.7% in 1990 to 40.6% in 1998. In light of the growing pool of susceptible individuals at older ages, with HAV continuing to circulate in the communities, evaluation of the feasibility of vaccination programs would be judicious.

Seroprevalence of parvovirus B19 in urban Chilean children and young adults, 1990 and 1996

An immunofluorescence test for detecting parvovirus B19 IgG was developed by infecting insect cells with recombinant baculovirus expressing the capsid protein VPI. The test was used to study the prevalence of antibodies in 725 healthy children and young adults living in Santiago, Chile. In total, 248 sera were taken in 1990 and 477 in 1996. The seroprevalence was low in children less than 5 years old (3% in 1990 and 21% in 1996). It rose during school age to a prevalence around 50%, reaching 60% in young adults. No differences were found between genders. There was a statistically significant higher seroprevalence in the low socioeconomic status group in 1990 samples, but this was not observed in 1996. The higher prevalence observed in children less than 5 years of age in 1996 compared with 1990 could be explained by the occurrence of intervening epidemics of parvovirus B19 infection.

Vaccination against hepatitis A in children aged 12 to 24 months [corrected]

BACKGROUND

Current hepatitis A vaccines are either licensed for children >2 years of age, as in the U.S. or Chile, or >1 year of age, as in Europe and other parts of the world. Recent recommendations for immunization against hepatitis A have included routine vaccination of children in areas or regions of higher endemicity. However, data on hepatitis A vaccination in toddlers aged between 1 and 2 years are scarce.

METHODS

This open clinical study investigated the reactogenicity and immunogenicity of two doses (0, 6-month schedule) of an inactivated hepatitis A vaccine (Havrix pediatric, Glaxco SmithKline Biologicals, Rixensart, Belgium) in 120 seronegative children aged 12-24 months.

RESULTS

Pain at the injection site and irritability were the most frequently reported local and general symptoms, respectively. No serious adverse events related to the study vaccine were reported. One month after the first dose, all but one subject had antibodies against hepatitis A with a GMT of 159 mIU/mL. After the booster dose, all had antibodies with a GMT of 2,939 mIU/mL.

CONCLUSIONS

Our data show that the inactivated hepatitis A vaccine was well tolerated by these toddlers and that the vaccine elicits a good immune response.

Regional lymphadenopathy in cat-scratch disease: ultrasonographic findings

BACKGROUND

Cat-scratch disease (CSD) is considered to be an emerging disease worldwide and is caused by Bartonella henselae, a gram-negative bacterium introduced by a scratch or bite of a cat. The most common clinical manifestation is regional lymphadenopathy, but clinical recognition may be difficult, as atypical manifestations may occur. The diagnosis is confirmed with serologic testing and histology is rarely needed. This paper is based on our experience with the use of ultrasonography in the diagnosis of CSD.

OBJECTIVE

The aim of this study was to describe the sonographic and color Doppler appearances of regional lymphadenopathy in CSD, as this has not widely reported in the literature.

MATERIALS AND METHODS

Forty-seven patients (average 9.4 years) were included who all had serologically and/or histologically proven CSD and had been studied using US early in the clinical course. All had a positive history of exposure to cats and exhibited regional lymphadenopathy.

RESULTS

US showed large hypoechoic adenopathy with some transmission enhancement and high vascularization on color-flow Doppler imaging. In 30 patients, abdominal US was also performed and splenic and/or hepatic granulomata were found in 10.

CONCLUSIONS

In our experience, sonography and especially color-Doppler and power-Doppler sonography was helpful in the diagnosis of CSD. We believe it should be used in the initial study of children with regional lymphadenopathy, and serologic testing should be performed when CSD is suspected.

Time course of antibody response to tetanus toxoid and pneumococcal capsular polysaccharides in patients infected with HIV

The temporal course of the humoral immune response to T-cell-dependent and T-cell-independent type 2 antigens was evaluated in HIV-infected patients. In all, 26 seropositive patients were vaccinated with tetanus toxoid and 23-valent pneumococcal vaccines; total IgG and IgG1 antibodies to tetanus toxoid (Ttox) and total IgG and IgG2 antibodies against 23 Streptococcus pneumoniae capsular antigens (PPS) were measured at baseline, 2 months, and 12 months after vaccination. For the Ttox, baseline levels of IgG1 (Ttox-IgG1) increased from 11.0 to 19.5 mg/L at 2 months postimmunization. Overall only 6 patients (23%) showed a significant response. At 12 months postvaccination, Ttox-IgG and T-tox-IgG1 were significantly lower than baseline levels (Ttox IgG basal; 11.0 mg/L, 12 months; 0.8 mg/L, Ttox IgG1 baseline; 13.1 mg/L, Ttox IgG1 12 months; 2.4 mg/L) and in 10 patients, antibodies that fell below protective levels (0.6 mg/L). In contrast with PPS, a significant response was observed at 2 and 12 months (PPS-IgG basal; 35.9 U/ml, 2 months; 151.4 U/ml, 12 months; 59.7 U/ml; PPS-IgG2 baseline 20.3 U/ml, 2 months; 113.2 U/ml, 12 months; 51.9 U/ml). Overall, 19 patients (76%) showed an immune response to pneumococcal polysaccharides antigens. Immunization with the Ttox T-cell-dependent antigen fails to elicit a significant immune response and may induce inhibition of antibody production in HIV-infected patients. In contrast, immunization with a T-cell-independent type 2 antigen can cause the pneumococcal polysaccharides to induce significant immune response in a high proportion of HIV-infected patients.

[Resistance of human immunodeficiency virus (HIV) to zidovudine. Genotypic analysis in strains isolated from Chilean patients]

BACKGROUND

Resistance of HIV to AZT is the result of mutations in the pol gene that codifies the enzyme reverse transcriptase.

AIM

To assess the resistance to antiretroviral drugs in Chilean patients infected with HIV.

MATERIAL AND METHODS

The presence of mutations was searched in 22 patients infected with HIV. The emergence or persistence of these mutations was studied in sequential samples of 19 patients. The presence of the mutation that confers resistance to didanosine (DDI) was studied in those subjects exposed to the drug. Polymerase chain reaction techniques were used to analyze mutations in codons 41, 70 and 215 of the pol gene (resistance to AZT) and the mutation in codon 71 (resistance to DDI).

RESULTS

On admission, none of the patients without previous exposure to AZT had drug resistance mutations. Seven of 12 patients (58.3%) that had received AZT had mutations in codon 215. In two, they were associated to a mutation in codon 41 and in two, a mutation in codon 70. After a mean follow up of 14 months, 13 of 15 patients (86%) that received AZT had viral strains genotypically resistant to the drug. In nine of these, the resistance was associated with disease progression. None of the 10 patients that received DDI had the mutation in codon 74 that confers resistance to the drug. However, in one of these patients, that never received AZT, a virus with a mutation in codon 215 was detected.

CONCLUSIONS

A high percentage of patients that have received monotherapy with AZT have genotypic resistance to the drug. This resistance is associated with clinical and immunological derangement in 70% of these subjects.

[Seroprevalence of cytomegalovirus and Toxoplasma gondii in healthy subjects under 30 years old in Santiago, Chile]

BACKGROUND

Infections by Cytomegalovirus and Toxoplasma gondii are endemic in Chile and only a low proportion of infected individuals have clinical manifestations.

AIM

To study the prevalence of infection by Cytomegalovirus and Toxoplasma gondii in Chile.

SUBJECTS AND METHODS

The prevalence of IgG antibodies against Cytomegalovirus and Toxoplasma gondii were studied in 560 subjects under 30 years old, using an ELISA technique. Age, socioeconomic level, breast feeding, assistance to nurseries and number of family members were considered as risk factors for these infections.

RESULTS

Infection by Cytomegalovirus had a global prevalence of 60%. It showed an epidemiological pattern of late acquisition in high socioeconomic levels and a pattern of early infection in medium and low socioeconomic levels. Eighty to 90% of sera were positive for the infection in adult subjects of the three socioeconomic levels. There was a positive correlation between the duration of breast feeding and the frequency of Cytomegalovirus infection. Infection by Toxoplasma gondii had a global prevalence of 24.6%. The rates of susceptible individuals were 80 and 50% in high and medium-low socioeconomic levels respectively.

CONCLUSIONS

The knowledge about the frequency of these infections in high risk populations such as women during their reproductive years and immunodepressed individuals, will allow the implementation of preventive measures.

Efficacy of a vancomycin solution to prevent bacteremia associated with an indwelling central venous catheter in neutropenic and non-neutropenic cancer patients

We evaluated the efficacy of a vancomycin solution in the prevention of bacteremia caused by vancomycin-sensitive organisms (VSO) in cancer patients with a tunneled central venous catheter (CVC). Eighty-three patients who had a single lumen CVC were randomized to use a heparin solution (25 U/ml) for daily catheter flush with (HepVan) or without (Hep) vancomycin, 25 mcg/ml. Febrile episodes were recorded, and central and peripheral blood cultures were drawn before beginning antibiotic therapy. Patients participated in follow-up to 16,677 catheter days (8,666 Hep and 8,011 HepVan), and 143 febrile episodes were recorded (82 Hep and 61 HepVan). Forty-four episodes of bacteremia occurred, 23 of them due to VSO (16 occurred in the Hep group and 7 in the HepVan group (P = 0.19). VSO bacteremia occurred in 14 neutropenic (absolute neutrophil count < 500 x 10(9)/l) episodes (7 Hep vs. 7 HepVan) and in 9 non-neutropenic episodes (9 Hep vs. O HepVan; P = 0.013). Vancomycin effectively prevented bacteremia by VSO in non-neutropenic patients, supporting the idea that intraluminal colonization of indwelling CVCs contributes to bacteremia only in these patients.

T84 cells in culture as a model for enteroaggregative Escherichia coli pathogenesis

Enteroaggregative Escherichia coli (EAEC) is an important cause of persistent diarrhea in many developing parts of the world, yet the pathogenetic mechanisms of EAEC diarrhea are unknown. Experiments with animal models suggest that EAEC strains damage the intestinal mucosa, and a putative cytotoxin has been described. To characterize the mucosal effects of EAEC, we studied strain 042, which we have shown to cause diarrhea in adult volunteers. Strain 042 was incubated in an in vitro organ culture model with biopsy-derived normal intestinal mucosa from pediatric patients. Strain 042 adhered strongly to samples of jejunal, ileal, and colonic mucosa. In addition, scanning electron microscopic examination of in vitro-infected intestinal biopsies revealed cytotoxic effects marked by exfoliation of mucosal epithelial cells. To develop an in vitro model to study these effects, we incubated 042 with polarized monolayers of the human intestinal epithelial cell lines Caco-2 and T84. Strain 042 adhered strongly to T84 cells but not to Caco-2 cells. T84 cells infected with 042 displayed marked toxic effects, most prominently in areas where bacteria were adhering. The apical membrane of damaged cells exhibited vesiculation and shedding of microvilli. The cytoplasm of affected cells displayed subnuclear vacuolization, and in some cases, nuclei of affected cells became separated from the surrounding cytoplasm. Severely affected cells ruptured, releasing their nuclei. Vacuolated remnant cells were seen throughout the monolayer. Strain 042 was not internalized by T84 cells. We concluded that EAEC strain 042 alters intestinal cell morphology, ultimately leading to cell death. Although the factor(s) required for this effect remains to be elucidated, T84 cells may serve as a valuable model in EAEC pathogenesis studies.

[Bartonella henselae infection in immunocompetent patients: cat scratch disease]

BACKGROUND

Cat scratch disease, whose etiologic agent is Bartonella henselae, is a benign disease in immunocompetent subjects, characterized by lymphadenopathy of prolonged course and occasional involvement of other organs such as liver, spleen, central nervous system, eye and lung. In immunocompromised patients, the infection is bacteremic and disseminated.

AIM

To report Chilean cases of cat scratch disease.

PATIENTS AND METHODS

Ten children (seven male, aged between 6 and 13 years old) with histologically or serologically confirmed cat scratch disease are reported.

RESULTS

Lymphadenopathy location was pre auricular in four cases, axillary in two, inguinal in two and epitrochlear in two. Three children had fever over 39 degrees C and two had a parinaud syndrome. Nine children had a history of cat scratch and one of a cat byte. Six had an erythrocyte sedimentation rate over 40. Lymph node ultrasound examination was a useful diagnostic tool. Two patients had splenic granulomas. Lymph node biopsies were obtained in four cases, showing a suppurative granulomatous lymphadenitis in all and a positive Warthin-Starry stain in two. Serology, done in patients without histological confirmation was positive with titles ranging from 1:64 to 1:8192. All patients had a satisfactory outcome with regression of lymphadenopathy.

CONCLUSIONS

Infections by Bartonella hemselae occur in the Chilean population and must be considered in the differential diagnosis of regional lymph node enlargement.

[Natural history of human immunodeficiency virus infection in a cohort of Chilean patients]

We characterized clinical manifestations and the risk to develop AIDS in a cohort of 32 patients infected with human immunodeficiency virus without AIDS A multivariate analysis was performed to determine association between the progression of infection and control variables (socioeconomic level, age, sex and sexual preferences) and causal variables (psycho-social changes, significant clinical events, stress scoring and sexual activity). The cumulative AIDS incidence, defined as a CD4 lymphocyte count below 200 cells/cm3 was 50% at 6.5 years and 82% at 8 years. Using clinical criteria to define AIDS, 50% developed the disease at 8 years of follow up. Among studied factors, only age (faster progression at higher age) and time of evolution were associated with progression in stages before AIDS, the most frequent diseases were acute diarrhea, sexual transmission diseases, oral candidiasis, sinusitis and varicella zoster infections. The reduction; of CD4 lymphocytes-below 200 cells/cm3 always preceded the symptoms of the disease. Two patients have remained more than eight years without clinical or immunological deterioration.

Structural studies of the O-antigenic polysaccharides of Escherichia coli O3 and the enteroaggregative Escherichia coli strain 17-2

The polysaccharide part of the lipopolysaccharide isolated from an enteroaggregative Escherichia coli isolated from a young child with diarrhoea in Santiago, Chile (strain 17-2), has been investigated. Sugar and methylation analyses of native and partially degraded polysaccharide together with 1H-NMR and 13C-NMR spectroscopies revealed that the polysaccharide is composed of pentasaccharide repeating units. The structure of the repeating unit of E. coli strain 17-2 O-polysaccharide is: [formula: see text] The structure of the O-polysaccharide from E. coli O3 was shown to be identical to that of E. coli strain 17-2 by sugar and methylation analyses and by 1H-NMR and 13C-NMR spectroscopies.

Seroprevalence of Helicobacter pylori in Chile: vegetables may serve as one route of transmission

Helicobacter pylori infection is very common in Chilean adults, but the age-related prevalence, risk factors for infection, and mode of transmission in Chilean children are unknown. An ELISA was used to test for H. pylori antibodies in 1815 Chileans < 35 years of age. Seropositivity was > 60% in lower socioeconomic groups. H. pylori seropositivity correlated with increased age, low socioeconomic status, and consumption of uncooked vegetables by use of a logistic regression analysis. Risk factors that reached marginal significance were consumption of uncooked shell-fish, female sex, and residence in Santiago. Although multiple modes of transmission for H. pylori undoubtedly exist, prior studies have suggested that contamination of irrigation water by raw sewage (and the subsequent contamination of vegetables that are eaten uncooked) is a key factor in the transmission of enteric pathogens in Chile; H. pylori may be transmitted by a similar route.

Structural studies of the O-antigenic polysaccharide of an enteroaggregative Escherichia coli strain

The polysaccharide part of the lipopolysaccharide obtained from an enteroaggregative Escherichia coli strain isolated from a young child with diarrhoea in Santiago, Chile (strain 73-1) was investigated. Sugar and methylation analyses of native and partially degraded polysaccharide together with 1H-NMR and 13C-NMR spectroscopy revealed that the polysaccharide is built of pentasaccharide repeating units. The structure of the repeating unit of E. coli strain 73-1 O-polysaccharide is (formula: see text)

Comparison of two assay methods for patterns of adherence to HEp-2 cells of Escherichia coli from patients with diarrhea

To determine whether methodological differences in the HEp-2 adherence assay could explain conflicting results of field studies, 244 strains of Escherichia coli from Mexican children with diarrhea were tested for patterns of adherence by the method used at the Center for Vaccine Development, University of Maryland (CVD), and at the Center for Infectious Diseases, University of Texas Medical School and School of Public Health (UTH). The CVD assay differentiated three phenotypes of adherent E. coli, including localized, diffuse, or aggregative adherence (LA, DA, or AA, respectively). There was agreement on pattern of adherence in 241 of the 244 strains (98.8%) tested by the CVD method in both Baltimore and Houston, and AA+ was the most common phenotype (28.5% of isolates). Among these isolates, the UTH assay detected only two adherent phenotypes (LA and DA), since it did not distinguish the AA pattern. The LA+ strains detected by each assay were compared for positivity with the enteropathogenic E. coli adherence factor (EAF) gene probe. Of the 16 strains LA+ by the CVD method, 100% were EAF+; in contrast, only 11 of 22 strains LA+ by the UTH method were EAF+ (P = 0.00074). These results help explain why in pediatric field studies in Mexico where isolates were tested by the UTH method (J. J. Mathewson, R. A. Oberhelman, H. L. Dupont, F. J. de la Cabada, and E. V. Garibay, J. Clin. Microbiol. 25:1917-1919, 1987) LA+ strains often did not belong to enteropathogenic E. coli O serogroups and why the AA pattern was not observed; the opposite was found in studies of pediatric diarrhea in Chile in which the CVD assay was used (M. M. Levine, V. Prado, R. M. Robins-Browne, H. Lior, J. B. Kaper, S. Moseley, K. Gicquelais, J. P. Nataro, P. Vial, and B. Tall, J. Infect. Dis. 158:224-228, 1988). Since it appears that both assays identify E. coli strains associated with diarrheal illness, the genetic relationships among these strains should be examined in future studies.

Detection by immune electron microscopy of 27-nm viral particles associated with community-acquired diarrhea in children

The proportion of diarrheal illnesses of unknown origin that were associated with small round virus (SRV, 23-38 nm) particles among children less than 2 years old attending an outpatient clinic in Baltimore was determined. During a 9-month period, stool specimens from 188 patients with acute diarrhea and 108 healthy age-matched control children were examined for enteric bacterial pathogens, protozoa, enteric adenovirus, and rotavirus. An enteropathogen was identified in 75 patients (40%) and in 21 controls (20%). A random sample of specimens without an identifiable pathogen was then examined for SRV particles by immune electron microscopy (IEM) using commercial human gamma globulin. Viruses of 26-30 nm diameter that were not enteroviruses were detected in specimens from 9 (12.5%) of the 72 patients and 1 (1.8%) of the 53 control subjects (P less than .04). Of 6 patients with available acute and convalescent sera, 4 demonstrated a significant immune response when tested by IEM. All patients experienced a mild, self-limited (1-3 days) illness. These findings suggest that SRV may be endemic in the Baltimore community and may result in clinically significant diarrheal illnesses.

Characterization of enteroadherent-aggregative Escherichia coli, a putative agent of diarrheal disease

Escherichia coli that exhibit the aggregative pattern of adherence to HEp-2 cells (enteroadherent-aggregative E. coli [EA-AggEC]) have been epidemiologically incriminated as a cause of diarrhea. We undertook a preliminary microbiological and pathogenetic characterization of 42 isolates of this putative pathogen. The strains were negative by tests with DNA probes for enteropathogenic, enterotoxigenic, enteroinvasive, and enterohemorrhagic E. coli and, by serotype, did not fit these categories. Thirty-nine of 42 strains had a 55-65-megadalton plasmid; many shared DNA homology. With one representative strain, plasmid transfer was accompanied by transfer of smooth lipopolysaccharide, fimbriae expression, and the aggregative property. EA-AggEC caused characteristic lesions in rabbit and rat ileal loops. The intestinal lesions and (Shiga-like) limb paralysis and death in rabbits inoculated with live organisms suggest toxin involvement; assays for Shiga-like toxins were negative. These preliminary results support the contention that EA-AggEC may represent a distinct category of diarrheagenic E. coli.

Morphological studies on fimbriae expressed by Vibrio cholerae 01

Colonization of the small intestine is an essential step in the pathogenesis of Vibrio cholerae diarrhea. At least one type of fimbriae, known as TcpA are required for the colonization process. This paper reports electron microscopic evidence that V. cholerae strains can express at least two other fimbrial types. Classical strains express three types: TcpA fimbriae are 5-6 nm in diameter and form bundles of parallel undulating filaments up to 15 micron long; Type B are 3 nm wide and of wavy morphology, and Type C are rigid, isolated filaments 5-6 nm wide and 180-800 nm long. El Tor strains express fimbriae resembling Types B and C. Types B and C were also found on a tcpA- isogenic mutant of V. cholerae 395 N1, and are thus encoded by genetically distinct loci. TcpA fimbriae, but not Types B or C, were labeled with gold-conjugated anti-TcpA antibody. Four El Tor strains, including two environmental isolates that poorly colonize humans, expressed fimbriae resembling Types B and C, but did not express TcpA. Multiple types of fimbriae may represent colonization factors for surfaces present in the environment and in the human gut. Characterization of the role of fimbriae in immunogen presentation and immunity could facilitate the improvement of cholera vaccines.

Molecular epidemiology of rotavirus infection in a room for convalescing newborns

In a prospective study, all patients admitted to a unit for convalescing newborns on an infant-toddler ward between January and April 1985 were tested every other day for rotavirus (RV) excretion by using an enzyme-linked immunosorbent assay. RNA electrophoresis of the RV strains identified in this population were analyzed to determine whether specific strains of virus were associated with infections in newborns. RV strains infecting older, symptomatic children from the infant-toddler ward were used for comparison. Among the 39 patients enrolled in the study, RV was detected in the stools of 13 (33%), 11 (86%) of whom were asymptomatic. Three different electropherotypes were seen among the newborns who were RV positive; these electropherotypes were identical to those identified in older children with community-acquired diarrhea and nosocomial-acquired diarrhea who were hospitalized on the infant-toddler ward during the same study period. Each of the three strains was first identified in the general ward and subsequently detected in the room with newborns within three to six days. We failed to identify a particular strain that exclusively infected newborns.