Design of a data set of qPCR primers for the early region of Human Papillomavirus oncogenic types 16 and 18.

High-Risk Human Papillomavirus (HR-HPV) types 16 and 18 are estimated to be responsible for 72.4% of all HPV-related cancers worldwide in both men and women, including cervical, anal, penile, vulval, vaginal and head and neck cancers [1]. Important efforts worldwide have devoted to the study of these genotypes, throughout epidemiology and basic science approaches. Of particular interest are the genes from the early region (E), coding non-structural proteins. Early genes E1 and E2 products are involved in replication and transcription regulation, while E6 and E7 proteins are recognised for their oncogenic potential. In this data report, we described a set of primers based on reference sequences from HPV16 and HPV18 designed to cover the early region of these oncogenic genotypes. The design was based on multiple sequences alignment to identify the less conserved regions along the open reading frames (ORFs) E6, E7, E1 and E2. The design allows a highly stringent real time PCR essay ranged from 123 to 598 bp overlapping products for HPV16 (12 products in total) and from 183 to 526 bp for HPV18 (11 products in total), both spanning the early genomic region. The high annealing temperatures (Ta) and regions selected for primer bind were intended for genotypic specificity, without compromising the qPCR amplification efficiency (≥ 90%). Evaluation of qPCR conditions for primer set was performed using DNA standards as controls, generated from the HPV16 and 18 genomes clones. This provides relevant information for further multiple quantitative real-time PCR analysis (qPCR), using the SYBR green chemistry, which is is more affordable than generating multiple fluorescently labeled probes.

Human Papillomavirus Genotypes Infecting the Anal Canal and Cervix in HIV+ Men and Women, Anal Cytology, and Risk Factors for Anal Infection.

The incidence of anal intraepithelial neoplasias associated with HPV is rising worldwide. In the general population, this pathology is rare, but individuals living with HIV/AIDS are at a significantly higher risk. We aimed to study HPV infection and performed cytological screening to study the epidemiological and behavioral determinants in a group of men and women living with HIV from a region in Mexico with high HIV incidence. This was a cross-sectional study including adults living with HIV/AIDS performed in Merida (Mexico). We invited patients of public HIV/STD clinics and those affiliated with social organizations of people living with HIV to participate in the study. Participants responded to an instrument to assess their risky behaviors and clinical history. Swabs from the anal canal and cervix and anal cytology specimens were obtained by medical staff from women and by self-sampling from men. For the 200 participants, 169 men and 31 women, anal HPV PCR tests resulted in 59.8% positivity (62.6% of men and 45.2% of women), and 17 genotypes were identified. The most frequent high-risk (HR) types for the anal canal were: HPV33 (35.3%), HPV58 (20.6%), HPV66 (18.6%), HPV45 (17.6%), and HPV16 (14.7%). Multiple genotypes were found in over 80% of the participants. Receptive anal intercourse in the previous 12 months, inconsistent condom use, and detectable HIV titers (≥50 cc/mL) were associated with HPV infection (p < 0.05). Cytology (smears and liquid-based) identified that 34.6% of the participants had low-grade squamous intraepithelial lesions (LSILs), and 3.5% had high-grade squamous intraepithelial lesions (HSILs). Neither HPV nor lesions were associated with low CD4+ counts (<200 cells/mm3, p > 0.05). Of the women, 60% were infected in the cervix and 45% in the anal canal, with an agreement of at least one genotype in 90%. The HR-HPV types associated with HSILs were HPV66, 33, 52, 51, 45, 18, and 68.

Human IgG antibody responses to severe acute respiratory syndrome coronavirus 2 viral antigens receptor-binding domain, spike, and nucleocapsid, in vaccinated adults from Merida, Mexico.

Several vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been approved for controlling the coronavirus disease 2019 (COVID-19) pandemic worldwide. Antibody response is essential to understand the immune response to different viral targets after vaccination with different vaccine platforms. Thus, the main aim of this study was to describe how vaccination with two distinct SARS-CoV-2 vaccine preparations elicit IgG antibody specific responses against two antigenically relevant SARS-CoV-2 viral proteins: the receptor-binding domain (RBD) and the full-length spike (S). To do so, SARS-CoV-2 protein specific in-house enzyme-linked immunosorbent assays (ELISAs) were standardized and tested against serum samples collected from 89 adults, recipients of either a single-dose of the Spike-encoding mRNA-based Pfizer/BioNTech (Pf-BNT) (70%, 62/89) or the Spike-encoding-Adenovirus-5-based CanSino Biologics Inc. (CSBIO) (30%, 27/89) in Merida, Mexico. Overall, we identified an IgG seroconversion rate of 88% (68/78) in all vaccinees after more than 25 days post-vaccination (dpv). Anti-RBD IgG-specific responses ranged from 90% (46/51) in the Pf-BNT vaccine at 25 dpv to 74% (20/27) in the CSBIO vaccine at 42 dpv. Compared to the S, the RBD IgG reactivity was significantly higher in both Pf-BNT (p < 0.004) and CSBIO (p < 0.003) vaccinees. Interestingly, in more than 50% of vaccine recipients, with no history of COVID-19 infection, antibodies against the nucleocapsid (N) protein were detected. Thus, participants were grouped either as naïve or pre-exposed vaccinees. Seroconversion rates after 25 and more dpv varies between 100% in Pf-BNT (22/22) and 75% (9/12) in CSBIO pre-exposed vaccinees, and 89% (26/29) and 73% (11/15) in Pf-BNT and CSBIO naïve vaccine recipients, respectively. In summary, observed seroconversion rates varied depending on the type of vaccine, previous infection with SARS-CoV-2, and the target viral antigen. Our results indicate that both vaccine preparations can induce detectable levels of IgG against the RBD or Spike in both naïve and SARS-CoV-2 pre-exposed vaccinees. Our study provides valuable and novel information about the serodiagnosis and the antibody response to vaccines in Mexico.

Infección por citomegalovirus humano en neonatos de un hospital público de Mérida, Yucatán / Human cytomegalovirus infection in neonates from a public hospital in Mérida, Yucatán

Resumen Introducción: El citomegalovirus humano es reconocido como la causa más común de infección viral congénita, la cual puede darse como resultado de infección primaria, reinfección o reactivación en la mujer embarazada; además, puede ocasionar retraso en el desarrollo neuronal y pérdida auditiva sensoneural en el neonato. Objetivo: Identificar la infección por citomegalovirus humano en neonatos por PCR en tiempo real (PCR-TR) y cultivo celular. Método: Estudio observacional, longitudinal y retrospectivo con muestras de hisopado oral provenientes de 362 neonatos nacidos en un periodo de 10 meses en un hospital público de Mérida, Yucatán. Se realizó PCR-TR para la detección de citomegalovirus humano. Se obtuvo cultivo celular primario de fibroblastos a partir de tejido de prepucio humano para recuperar el virus. Se siguieron solo los casos positivos. Resultados: Se encontró 0.86 % de infección por citomegalovirus humano por PCR-TR. No se recuperó el virus en cultivo. En las visitas de seguimiento, la salud sensorial y el neurodesarrollo fueron adecuados. Conclusión: La prevalencia de infección por citomegalovirus humano en neonatos fue similar a la de reportes mundiales y solo pudo evidenciarse por PCR. La infección asintomática detectada entre las 12 a 24 horas del nacimiento no tuvo consecuencias a largo plazo.

Abstract Introduction: Human cytomegalovirus (HCMV) is recognized as the most common cause of congenital viral infection, which can occur as a result of primary infection, reinfection or infection reactivation in the pregnant woman and be the cause of delay in neuronal development and sensorineural hearing loss in the neonate. Objective: To identify CMVH infection in newborns by real-time polymerase chain reaction (RT-PCR) and cell culture. Method: Observational, cross-sectional, retrospective study with oral swab samples from 362 neonates born within a 10-month period in a public hospital of Mérida, Yucatán. RT-PCR was carried out for the detection of HCMV. Fibroblast primary cell culture was obtained from human foreskin tissue to isolate the virus. Only positive cases were followed. Results: A prevalence of HCMV infection of 0.86 % was found by RT-PCR. No virus was isolated with cell culture. In the follow-up visits, sensory health and neurodevelopment were adequate. Conclusion: The prevalence of HCMV infection is similar to that of worldwide reports, and only was detected by RT-PCR. Asymptomatic infection detected 12-14 h after birth had no long-term health consequences.

Prevalence of anal infection due to high-risk human papillomavirus and analysis of E2 gene integrity among women with cervical abnormalities.

BACKGROUND: High-risk human papillomaviruses (HR-HPV) infection has been associated with 90% of anal cancer cases. Women with abnormal cytology are a high-risk group to develop anal neoplasia. The aim of this study is to describe the prevalence and epidemiology of HR-HPV 16, 18, 45, and 58 anal infections in women with cervical abnormalities, as well as to assess E2 gene integrity. METHODS: A cross-sectional study was performed on 311 cervical and 311 anal samples from patients with abnormal cytology in two colposcopy clinics in Yucatan, Mexico. A specific PCR for oncogenes was performed in order to identify HVP 16, 18, 45 and 58. Real time PCR was used to amplify the whole HPV 16, 18, and 58 E2 gene to verify its integrity in anal samples. RESULTS: High risk HPV 16, 18, 58, and/or 45 were found in 41.47% (129/311) of cervical samples, and in 30.8% (96/331) of anal samples, with 18% (57/311) of the patients being positive in both samples. The same genotypes in both anatomical sites were observed in 11.25% (35/311). The E2 gene was disrupted in 82% of all tested samples. The frequency of genome disruption viral integration in anal samples by genotype was: HPV 58 (97.2%); HPV 16 (72.4%), and HPV 18 (0%). CONCLUSION: Women with cervical disease have HR-HPV anal infections, and most of them have the E2 gene disrupted, which represents a risk to develop anal cancer.

Human papillomavirus and Chlamydia trachomatis infection in gyneco-obstetric outpatients from a mexican hospital.

CONTEXT: Human papillomavirus (HPV) and Chlamydia trachomatis are the most frequent sexually transmitted infections, usually asymptomatic. Persistent infection with high-risk HPV types and other cofactors such as the concomitant infection with C. trachomatis can represent a higher risk to develop cervical lesions; therefore, screening with sensitive methods could aid to identify women at risk. AIMS: The aim is to determine the prevalence and concurrence of both infections, detected with in-house molecular methods, and to identify the risk factors associated to the infections in Mexican women. SUBJECTS AND METHODS: This was a cross-sectional study including gynaecological-obstetrical medical outpatients from a Social Security Hospital in Southeast Mexico. After informed consent, cervicovaginal samples were collected and tested for HPV and C. trachomatis using polymerase chain reaction (PCR). HPV positives were further tested for high-risk HPV16, 18, 58 and low-risk 11 using real-time PCR. All methods employed were in-house. Data analyses included odds ratios (OR), Chi-square and linear regressions. RESULTS: Women included were 233, aging 15-49 (mean 30 years), 52.8% were pregnant. For HPV and C. trachomatis testing, 230 samples were adequate, resulting in 48 (20.9%) and 15 (6.5%) positives, respectively; 4 (1.7%) were positive to both. The most frequent genotype identified was HPV58 (25% of typified samples). C. trachomatis positives were 73% asymptomatic, none had pelvic inflammatory disease or infertility histories. The only variable associated to HPV infection was the history of previous sexually transmitted disease (OR = 3.69,P= 0.0019). CONCLUSIONS: More than 25% of the population was infected with either agent. We successfully used in-house molecular methodologies for diagnosis and typing, showing HPV and C. trachomatis prevalence consistent to previous reports. Concomitant infections were found, HPV high-risk types were involved in half of these cases, representing a higher risk.

Genetic Variability in E6 and E7 Oncogenes from Human Papillomavirus Type 58 in Mexican Women.

BACKGROUND/AIMS: The study aimed to describe human papillomavirus (HPV) 58 genetic variability in E6 and E7 oncogenes from women in southeast Mexico and their phylogenetic relationships with the sequences from other geographical regions. METHODS: The E6-E7 region was amplified by nested PCR, and sequenced for identification of polymorphisms, phylogenetic trees construction, and haplotype and fixation tests. RESULTS: HPV58 positive samples were obtained from a repository, 54 were amplified, 47 sequences for the E6 gene, and 51 sequences for the E7 gene were obtained. Fifteen new E6 mutations were found; the most frequent were G279T (G57V; 29.78%), T249G (F47C; 34.04%), and A270G (Y54C; 34.04%), and previously reported c307t (63.82%). For E7, 17 known mutations were found, the most frequent were C632T (T20I), 35.30%, G760A (G63S), 35.30%, and t744g 74.50%. No significant association with the severity of the lesions was found. The polytomy in the E6 tree did not allow proposing phylogenetic relationship, and E7 tree presented defined branches. All sequences were presumably A lineage, most closely related to A1 and/or A3 sublineage. HPV58 variants are not specific for a geographical area. Population and fixation analyses suggest a possible Asian origin of HPV58 from Yucatan. The most frequent E7 haplotype in Yucatan groups with other populations of the world. CONCLUSION: The genetic variability of HPV58 from Mexico was described for the first time. E7 was more conserved than E6. New mutants present exclusively in Yucatan were identified.

Analysis of E2 gene integrity in HPV16 and HPV58 viruses isolated from women with cervical pathology.

Integration of human papillomavirus (HPV) DNA into human cells accompanied by the disruption of the viral genome has been described as a prerequisite for cancer development. This study aimed to investigate E2 gene integrity of HPV16 and HPV58 viruses isolated from infected women with cervical lesions. Forty-two HPV16- and 31 HPV58-positive samples were analysed. E2 integrity was assumed when all fragments covering the E2 gene were amplified with specific polymerase chain reaction primers. Overall, in 59% of the samples, at least one fragment was not amplified in HPV16- (57%) and HPV58-positive samples (61%). Samples from high-grade squamous intraepithelial lesions had the highest frequency of E2 gene disruptions (73%), followed by samples from low-grade squamous intraepithelial lesions (63%) and, finally, samples from invasive cervical cancer (35%). Association between the integrity status of the E2 gene, and lesion grade was assessed by the chi-squared test applied to the combined set of viruses (p = 0.6555) or to populations of the same virus type (HPV58, p = 0.3101; HPV16, p = 0.3024). In conclusion, in this study, no association was found between the presence of E2 gene disruptions and the grade of cervical lesions caused by HPV16 and HPV58.

Epidemiology of oral HPV in the oral mucosa in women without signs of oral disease from Yucatan, Mexico.

High-risk human papillomaviruses (HR-HPV) are considered necessary for the development of cervical cancer. Furthermore, there is no doubt that some types of oral squamous cell carcinoma are associated with HR-HPV. The epidemiology of oral HPV infections in healthy subjects remains unclear due to a lack of knowledge. The objective of this study was to investigate the epidemiology of human papillomavirus infections of the oral mucosa without pathology. A cross-sectional study was performed; samples from 390 women seeking prenatal care, Pap smears, family planning or gynecological diseases were studied. Oral cells were collected by direct swab sampling. Information regarding sociodemographic status, sexual behavior, infectious diseases, contraceptive history and tobacco and alcohol consumption were obtained through direct interviews. HPV and genotypes were detected by type-specific polymerase chain reaction. Our results revealed that 14% of the women studied had an oral HPV infection. Women ≤ 20 years of age had the highest HPV prevalence (24.5%). In total, seven genotypes were identified, including the high-risk genotypes 16, 18, 58 and 59 and the low-risk genotypes 6, 81 and 13, the latter of which is a type exclusive to oral mucosa. Sexual behavior was not associated with the presence of genital HPV types in the oral mucosa. Genital HPV types were present in the oral mucosa of women without associated clinical manifestations; however, sexual behavior was not associated with infection, and therefore others routes of transmission should be explored.

Amino acid substitution D222N from fatal influenza infection affects receptor-binding properties of the influenza A(H1N1)pdm09 virus.

We have analyzed the receptor binding profile of A(H1N1)pdm09 recombinant influenza viruses containing the amino acid substitution D222N which has been associated with a fatal case of infection. This mutation was investigated in conjunction with a secondary mutation, S185N. Using human tracheobronchial epithelial cells (HTBE), we found that single mutation D222N affects the binding and replication of the virus during initial stages of infection, with limited but preferred tropism to non-ciliated cells expressing α2,6-SA. However, in conjunction with the S185N change, the (D222N, S185N) virus shows a remarkable increase in binding and replication efficiency, with tropism for both ciliated and non-ciliated cells. Glycan microarray analysis demonstrated correlation between the binding profile and the cell tropism observed in the HTBE cells. These findings suggest that viruses with D222N required compensatory mutations such as S185N to maintain viral fitness, and in combination, affect the pathogenicity of the virus and the clinical outcome.

Epidemiology of oral HPV in the oral mucosa in women without signs of oral disease from Yucatan, Mexico

High-risk human papillomaviruses (HR-HPV) are considered necessary for the development of cervical cancer. Furthermore, there is no doubt that some types of oral squamous cell carcinoma are associated with HR-HPV. The epidemiology of oral HPV infections in healthy subjects remains unclear due to a lack of knowledge. The objective of this study was to investigate the epidemiology of human papillomavirus infections of the oral mucosa without pathology. A cross-sectional study was performed; samples from 390 women seeking prenatal care, Pap smears, family planning or gynecological diseases were studied. Oral cells were collected by direct swab sampling. Information regarding sociodemographic status, sexual behavior, infectious diseases, contraceptive history and tobacco and alcohol consumption were obtained through direct interviews. HPV and genotypes were detected by type-specific polymerase chain reaction. Our results revealed that 14% of the women studied had an oral HPV infection. Women ≤ 20 years of age had the highest HPV prevalence (24.5%). In total, seven genotypes were identified, including the high-risk genotypes 16, 18, 58 and 59 and the low-risk genotypes 6, 81 and 13, the latter of which is a type exclusive to oral mucosa. Sexual behavior was not associated with the presence of genital HPV types in the oral mucosa. Genital HPV types were present in the oral mucosa of women without associated clinical manifestations; however, sexual behavior was not associated with infection, and therefore others routes of transmission should be explored.

Human papillomavirus infection and spontaneous abortion: a case-control study performed in Mexico.

OBJECTIVE: To investigate if HPV cervical infection is associated with spontaneous abortion in a Mexican population. STUDY DESIGN: Case control study including 281 women from two Social Security Hospitals in Merida, Mexico. Cases were women with spontaneous abortion attending for curettage, and controls were pregnant women at term who attended for delivery. HPV molecular detection and typing of HPV 16, 18, 58 and 6/11 was performed on cervical samples, and TORCH serology IgM tests (against T. gondii, CMV, HSV) were performed on cases. Data were analyzed using Chi square, odds ratio and linear regression tests. RESULTS: HPV global prevalence was 19.8% (24.4% in cases and 15.2% in controls). HPV types 16 and 58 were the most frequently detected in both groups. Multiple HPV types concurrent infection were found in 31.4% of typified samples. Amongst cases 27.3% of HPV positive women reported at least one previous pregnancy loss; compared to 17.43% amongst HPV negative women. Nevertheless, HPV was not significantly associated with spontaneous or to repetitive abortion. Cases were 60.2% positive to any TORCH agent, although it was not significantly associated to referred miscarriage history. Spontaneous abortion was associated to a previous pregnancy loss and to women's age older than 35 years old. HPV infection was significantly associated to alcohol intake before pregnancy and to multiple sexual partners. CONCLUSION: HPV cervical infection was not associated with spontaneous abortion. HPV in spontaneous abortion and other adverse pregnancy outcomes merits further study.

Factors associated with cervical cancer screening amongst women of reproductive age from Yucatan, Mexico.

This study aimed to analyse the participation of women of reproductive age in a cancer screening program, and survey reasons for non-screening in a region from Mexico with high cervical cancer mortality. A total of 281 obstetric patients from a previous HPV study in a social security hospital during 2008-2009 were included. Reasons for not participating in the screening were directly asked. HPV positive patients were invited to participate in an informative workshop, and they filled in a knowledge questionnaire. The women ranged in age from 14-47 years; 123 (43.8%) had never participated in screening, of which 97 (78.9%) had their first sexual intercourse 2 to 10 years ago, resulting in 25% HPV positive. Screening history was strongly associated with 2 or more gestations (OR= 10.07, p=0.00) and older age (OR=6.69 p=0.00). When 197 women were contacted and interviewed, reasons referred for non-screening were ignorance, lack of interest or time, recent sexual onset, shame and fear. More than 50% of the workshop participants showed knowledge of HPV, while 38.9% and 25% knew about Pap smear and cervical cancer. A high percentage of women of reproductive age have never had a Pap smear. Promoting the screening program in medical facilities seems to be important in this population. New approaches to inform vulnerable individuals on the benefits of screening need to be implemented, especially for young women.

Human papillomavirus 13 in a Mexican Mayan community with multifocal epithelial hyperplasia: could saliva be involved in household transmission?

Multifocal epithelial hyperplasia (MEH) is a disease of the oral mucosa. Human papillomaviruses 13 and 32 have been detected in these lesions. We describe the epidemiology and clinical characteristics of patients with MEH in a rural community in the Mayan area of Mexico with 53 cases and 54 controls. Clinical and epidemiological data were collected through a direct interview. Oral cell samples were collected with a cytobrush. Subjects collected their own saliva sample in a sterile bottle. All samples were tested for HPV 13 and 32 by polymerase chain reaction using specific primers. Of the 53 patients and 54 healthy subjects, 56% were < 12 years old, 25% were males and 75% females. Evolution of the lesions was between two months and 17 years. The lesions affected lips, jugal mucosa, and tongue, 96% had multiple lesions. From 53 patients, fifty samples of oral cells and 31 samples of saliva were analyzed. HPV 13 was detected in 100% oral cell and 100% saliva samples studied. 16 healthy subjects were HVP 13 positive. A highly significant association of HPV 13 infection and MEH was found, as determined by chi square test (p = 0.00) Household transmission of HPV 13 may happen through saliva and the shared use of contaminated objects.

Receptor binding profiles of avian influenza virus hemagglutinin subtypes on human cells as a predictor of pandemic potential.

The host adaptation of influenza virus is partly dependent on the sialic acid (SA) isoform bound by the viral hemagglutinin (HA). Avian influenza viruses preferentially bind the α-2,3 SA and human influenza viruses the α-2,6 isoform. Each isoform is predominantly associated with different surface epithelial cell types of the human upper airway. Using recombinant HAs and human tracheal airway epithelial cells in vitro and ex vivo, we show that many avian HA subtypes do not adhere to this canonical view of SA specificity. The propensity of avian viruses to adapt to human receptors may thus be more widespread than previously supposed.

Detection of human influenza virus in Yucatan, Mexico.

OBJECTIVE: Influenza virus is the most common cause of Acute Respiratory Infections (ARI) world wide. In patients with chronic condition, infection by the influenza virus can cause complications such as pneumonia which may have fatal outcome. The aim of this work was to determine the frequency of human influenza virus in outpatients with influenza-like illness (ILI) and in those patients admitted to hospital with community acquired pneumonia (CAP) in Yucatan, Mexico (October 1998-July 1999). MATERIALS AND METHODS: Throat swabs were collected from ILI and CAP patients and processed to detect respiratory viruses. All clinical samples were tested for seven respiratory viruses using a rapid indirect immunofluorescence test (IFI). Clinical samples with positive results for influenza virus by IFI were inoculated into chick embryo eggs and/or MDCK cells for viral isolation. All influenza virus isolates were typed using the WHO influenza Kit 1998-1999. RESULTS: A total of 288 clinical samples were collected. Influenza virus type A was diagnosed in 29 clinical samples (10%), no other respiratory viruses were identified. Influenza virus was present with 8.9% (17 out of 189) in ILI patients, whereas with 12.12% (12 out of 99) in CAP patients. Influenza virus was detected from December to July. Six viral isolates were obtained and identified as influenza A (H3N2). CONCLUSION: Human influenza virus is certainly a cause of ARI and pneumonia in Yucatan, Mexico. The results showed that influenza virus contributes to at least 8.9% of the ARI, and more importantly to 12% of CAP patients. Positive cases were present in a different pattern to temperate zones where the peak of incidence occurs during autumn and winter.

¿Pueden los mosquitos transmitir el virus de la inmunodeficiencia humana? / Can mosquitoes transmit human immunodeficiency virus?

La transmisión del virus de la inmunodeficiencia humana (VIH) se conoce ocurre por contacto sexual, perinatalmente, y por exposición a sangre infectada o productos sanguíneos entre otros. Preguntarse si existe la posibilidad de transmisión del VIH por insectos hematófagos de personas infectadas a personas no infectadas ha sido y es un punto de intensa discusión. Las rutas clásicas de transmisión de patógenos por artrópodos chupadores de sangre son "mecánica" o "biológica". Ambas rutas son rechazadas, la última porque no existe replicación de retrovirus en el vector y su sobrevivencia en el artrópodo es muy limitada. La persistencia del VIH en un insecto o en sus partes bucales es uno de los numerosos factores necesarios para la transmisión mecánica en la naturaleza. El riesgo de transmisión del VIH por insectos parece ser extremadamente bajo o inexistente. En este artículo de revisión se exponen las razones y evidencias científicas que nos permiten concluir porque la transmisión del virus VIH por mosquitos no es posible.

Influenza: Historia de una enfermedad / Influenza: History of a disease

En los pasados 400 años, las epidemias de influenza han sido reportadas en muchos países. Las epidemias desde siglo XVI en Inglaterra y la del siglo XVIII en USA, son reconocidas como influenza, aun con la ausencia del conocimiento preciso del agente causal. La pandemia de influenza de 1918 fue la más grande en la histoira actual, causando 20 millones de muertes en todo el mundo. En los tiempos modernos desde 1957 y 1968 las pandemias de influenza han matado cerca de un millón de personas. Mientras que la relación entre el cambio antigénico y epidemia es algo complejo, involucrando numerosos factores atribuibles al huésped y a los virus. Los cambios "drift" y giros "shift" antigénicos, son los marcadores que mejor se pueden identificar con potencial pandémico