Prevalence of HPV infection in hypopharyngeal and laryngeal squamous cell carcinoma at Thailand's largest tertiary referral center.

BACKGROUND: Following the well-established relationship between human papillomavirus (HPV) and cervical carcinoma, the carcinogenicity of this virus has also been confirmed in subsets of head and neck carcinoma (HNCA), but mainly in the oropharynx. Other subsites of HNCA with less known association to HPV have never been studied in Thailand. Accordingly, the aim of this study was to investigate the prevalence of HPV DNA in hypopharyngeal and laryngeal squamous cell carcinoma in Thai population. METHODS: This cross-sectional study included hypopharyngeal and laryngeal squamous cell carcinoma patients diagnosed and treated at the Department of Otorhinolaryngology, Siriraj Hospital during the September 2011-December 2013 study period. Presence of HPV genome was confirmed by polymerase chain reaction from pathologically-confirmed fresh specimens. Demographic data and risk factors of HPV infection were evaluated. RESULTS: Eighty patients were included, and 95% of those were male. Only one patient was noted with positive HPV-62 serotype. Most patients consumed tobacco and/or alcohol. Five patients had no risk factors for cancer development. Risk of HPV infection was evaluated by self-reporting questionnaire. The mean age of sexual debut was 20.17 years. Forty-eight patients had multiple sexual partners. Sixteen and seven patients had history of sexually transmitted disease infection and habitual oral sex contact, respectively. CONCLUSION: There was no oncogenic HPV DNA detected within pathologic specimens of laryngeal and hypopharyngeal cancers in this study. Compared to rates reported from developed countries, the prevalence of HPV-related HNCA in Thailand is very low.

Duration of neutralizing antibody persisting in Thai individuals after childhood vaccination against smallpox.

BACKGROUND: Although smallpox was completely eliminated by 1980, it remains possible that variola virus could be intentionally released in an act of bioterrorism. Thus, several studies have been performed to detect antibody levels after smallpox vaccination of the current population in various countries to indicate the duration of maintenance of immunological memory. Our study endeavored to investigate the level of neutralizing (Nt) antibody responses of Thai individuals who had been immunized with smallpox vaccine during childhood. METHODS: The plaque reduction neutralization test (PRNT) was used to study vaccinia Nt antibody responses in sera of individuals ranging in age from 35-4, 45-54, 55-64, 65-74, 75-84 and > 84 years old, referred to as groups 1-6, respectively. Each group included 200 sera: 100 male sera and 100 female sera. RESULTS: An incubation time of 15 hours for sera and vaccinia virus was confirmed to be the optimal incubation period for PRNT. Positive Nt antibody titers (≥32) were detected in 135 (11.25%) of 1,200 sera: 81 (6.75%) male sera and 54 (4.5%) female sera. There were 4 (2%), 11 (5.5%), 19 (9.5%), 16 (8%), 33 (16.5%), and 52 (26%) positive sera in groups 1-6, respectively. Interestingly, the oldest individual with positive Nt antibody was a 98-year-old female. Two males aged 96 and 91 years old had the highest Nt antibody titers. CONCLUSIONS: Our data suggests that the vaccinia-specific Nt antibody response in the current Thai population could be maintained for more than 90 years after vaccination. However, the majority of the Thai population aged ≥35-74 years old is still highly susceptible to infection.

Human Papillomavirus Infection in Oral Cavity and Oropharyngeal Cancers: Are They the Same Story?

Background: Nowadays, human papillomavirus (HPV) infection becomes the main risk factor for head and neck cancer development. In Thailand, the related role of this viral infection to head and neck cancer is still unknown and not well established. Objective: To identify different characteristics of oral cavity and oropharyngeal cancer, and to determine the HPV-associated prevalence of these two tumor types in Thailand, which is unlike the Western countries. Material and Method: Between 2010 and 2012, a cross-sectional study was performed in 23 oral cavity and 23 oropharyngeal cancer patients. HPV genome was studied in all of them from pathological confirmed fresh specimens. Risks of HPV infection were collected using self-reported questionnaire. Results: The prevalence of HPV-related oropharyngeal cancer was significantly noted in 26.09% (p = 0.009), while no demonstrable HPV-associated prevalence in oral cavity cancer. In addition, the routes of HPV infection were not identifiable. Conclusion: Oral cavity and oropharygeal cancers are not only anatomically distinct, but also greatly differed in their characteristics and pathophysiology. The percentage of HPV-related tumors in Thailand is considerably low when compared to the Western countries. However, the impact on treatment modification cannot yet be universally applied.

Simultaneous discrimination and detection of influenza A(H1N1)pdm09 and seasonal influenza A viruses using a rapid immunogold biosensor.

A rapid immunogold biosensor for the simultaneous discrimination of influenza A(H1N1)pdm09 and seasonal influenza A viruses was developed successfully. Monoclonal antibodies (mAbs) that were specific for the hemagglutinin protein of the A(H1N1)pdm09 virus were produced, and the best mAb pairs were selected. Using an mAb that was specific for the influenza A nucleoprotein, a rapid immunogold biosensor for the discrimination and detection of A(H1N1)pdm09/seasonal influenza viruses was developed. When tested with 72 virus isolates, the system achieved 100 % detection of the A(H1N1)pdm09 virus without cross-reactivity against seasonal influenza A (H1, H3 subtypes) and B viruses, parainfluenza viruses, respiratory syncytial viruses, and adenoviruses. The detection limits for A(H1N1)pdm09 and seasonal strains were 5 × 10(2)-7.5 × 10(3) and 1 × 10(3)-7.5 × 10(5) TCID50/mL, respectively. When tested with 49 clinical specimens, the specificity was high (100 %). The sensitivity for the detection of A(H1N1)pdm09 and seasonal strains was 90 % and 100 %, respectively, which correlated with the results of real-time reverse transcription polymerase chain reaction as a reference method. The ability of the system to detect and discriminate the A(H1N1)pdm09 strain from the seasonal strains suggests that this method may be beneficial for investigation of outbreaks and diagnostic applications. Furthermore, this method might be a useful platform for developing a rapid diagnostic system for the simultaneous discrimination of other influenza virus subtypes during future outbreaks.

Serological response of patients with influenza A (H1N1) pdm09-associated pneumonia: an observational study.

BACKGROUND: Little is known about the dynamics or magnitude of antibody response in patients with influenza A (H1N1) pdm09-associated pneumonia. We described and compared the antibody response to influenza A (H1N1) pdm09 in patients with and without pneumonia. METHODS: We collected serum samples and determined antibody titers by the hemagglutination inhibition (HI) and microneutralization (mNT) assays from patients with RT-PCR confirmed influenza A (H1N1) pdm09 virus at baseline, 1, 2 and 6 months after onset of illness. RESULTS: Fifty-nine patients were enrolled, 45 (76.3%) were between 15 and 60 years of age, 49 (83.1%) were hospitalized and 25 (42.4%) had complications with pneumonia. Ninety-four percent of patients had HI titers ≥ 1: 40 and 90% had mNT titers ≥ 1: 160 at 2 months after illness. Geometric mean titers (GMT) of HI and mNT increased significantly (p<0.001) between baseline and months 1 or 2, then declined significantly (p<0.001) at month 6 by the HI assay, but dropped to an insignificant level (p=0.24) by the mNT assay. The mNT-GMT was at least twice as high as corresponding HI antibodies over a 6 month period. The GMT of HI and mNT in those with pneumonia (1 mo) peaked earlier than that of those without pneumonia (2 mo). When adjusted by age and gender, those with pneumonia had a higher HI-GMT than those without pneumonia at 1 month (264 vs. 117, p=0.007), 2 months (212 vs. 159, p=0.013), and 6 months (160 vs. 82, p=0.018). CONCLUSIONS: The patients recovered from influenza A (H1N1) pdm09-associated pneumonia, clearly developed an earlier and more robust antibody response until 6 months after onset of illness. The results in our study are useful to determine an appropriate donor and timing to obtain convalescent plasma for adjunctive treatment of seriously ill patients with pandemic H1N1 influenza.

Antiherpetic Effects of Gynura procumbens.

The ethanol extract of Gynura procumbens showed virucidal and antireplicative actions against herpes simplex virus HSV-1 and HSV-2. It was further chromatographed on MCI gel CHP20P column giving the extract fractions F1 (water), F2 (water-methanol) F3 (methanol), and F4 (ethyl acetate). All but F1 had virucidal action against both viral types. We reported here the active compounds from F2 and F3. The antiherpetic compounds of F2 was a mixture of dicaffeoylquinic acids with virucidal and antireplicative actions against HSV-2 (IC50 96.0 and 61.0 µ g/mL, resp.) Virucidal compounds of F3 were a mixture of ß -sitosterol and stigmasterol (IC50 250.0 µ g/mL against HSV-1), a mixture of ß -sitosteryl and stigmasteryl glucosides (IC50 50.0 µ g/mL against HSV-2) and 1, 2-bis-dodecanoyl-3- α -D-glucopyranosyl-sn-glycerol (IC50 of 40.0 µ g/mL against HSV-2). Herbal products containing 1 and 2% of standardized ethanol extract were prepared. Double-blind randomized controlled clinical trial of the products was performed in patients with recurrent herpes labialis. Results showed that the number of patients, whose lesions healed within 7 days and the average healing time of both groups differed insignificantly. Viral culture on D7 indicated a decrease of infected patients from 48.7% to 7.69% in treated group whereas in placebo group the infected patients decreased from 31.25% to 20.00%. The viral reduction in treated group indicated the benefit of the product. Insignificant result might arise from a low number of participated patients and insufficient concentration of plant extract in herbal product.

Application of ImageJ program to the enumeration of Orientia tsutsugamushi organisms cultured in vitro.

The ImageJ program was applied to the enumeration of Orientia tsutsugamushi organisms in cell culture using indirect immunofluorescence assay (IFA). The highest correlation (r=0.984) was observed between manual counting methods and the ImageJ program (MaxEntropy threshold algorithm). This software-based methodology is cheaper, more standardised and better reproducible than a manual-based approach.

HIV-1 neutralization by monoclonal antibody against conserved region 2 and patterns of epitope exposure on the surface of native viruses.

BACKGROUND: Conserved neutralizing epitopes are considered to be a key role for eliciting broadly neutralizing antibody (NAb). Previously, two conserved neutralizing epitopes of HIV-1 CRF01_AE envelope were identified at amino acid 93-112 of the C1 (C1E) and at 218-239 of the C2 (C2E) regions. To access the potency of antibody directed against conserved epitopes, a monoclonal antibody (MAb) specific to the C2E region was developed and characterized. METHODS: The immunogenicity of two epitopes was examined by immunizing BALB/c mice with the matching synthetic peptides. One MAb, C2EB5, directed against peptide C2E, was generated by conventional methods, while C1E1 and C1E2 peptides induced slight antibody response in mice. The neutralizing activity of MAb C2EB5 was examined using a peripheral blood mononuclear cell (PBMC) based method and various HIV-1 subtypes including A, B, C, D, and CRF01_AE; C2EB5 was compared with other known neutralizing MAbs (4E10, 447-52D) and with sCD4. The exposure of the C2 epitope on native virus was investigated using virus capture by these MAbs. RESULTS: The MAb C2EB5 demonstrated cross-neutralization against various HIV-1 subtypes. The overall potency of MAb C2EB5 against 5 subtypes was ranked in the following order: subtype C> CRF01_AE> subtype D> subtype A> subtype B. The epitope exposure for MAb C2EB5 was also correlated with the neutralization properties of each subtype. CONCLUSION: This study demonstrates the cross-clade neutralizing activity of a MAb directed against an epitope located in the C2 region of the HIV-1 env and highlights differences in the exposure of antigenic epitopes on the surface of various HIV-1 subtypes. The epitope for this newly identified neutralizing MAb made against a subtype CRF01_AE peptide is particularly exposed in subtype C viral isolates.

Structure and function of HIV-1 CRF01_AE envelope proteins from blood and genital fluid isolates.

The recombinant envelope protein (gp120) of the human immunodeficiency virus type 1 (HIV-1) CRF01_AE env gene isolated from the corresponding blood (rgp120-F36PC) and genital fluid (rgp120-F36VC) specimens obtained from HIV infected individuals was successfully produced in both prokaryote and eukaryote cells. The yields of HIV-1 recombinant envelope proteins rgp120-F36PC and rgp120-F36VC produced in E. coli and in mammalian cells were 1.0 and 1.2, and 0.3 and 0.5 mg/ml, respectively. Antibody responses in mice immunized with rgp120-F36VC protein were not significantly higher than those with rgp120-F36PC protein. The level of antibody response in mice immunized with V3 deleted recombinant gp120 proteins from rgp120-F36VC and rgp120-F36PC was not significantly different from wild type rgp120 proteins. beta-strands at the tip of the V3 loop of the HIV-1 envelope protein were predicted for the wild type genital fluid isolate but not for the wild type blood isolate. The replication capacity of both F36PC and F36VC was quite efficient. The infectivity assay of the epithelial cell line for pNL4-3/gp120F36VC was better than for pNL4-3/gp120F36PC. The extra beta-strands in the V3 loop may be involved in cell tropism.

Asthma, bronchial hyper-responsiveness and Chlamydophila (Chlamydia) pneumonia infection in adult Thai population.

BACKGROUND: The associations between Chlamydophila (Chlamydia) pneumonia infection and chronic asthma or bronchial hyper-responsiveness (BHR) have been inconclusive. OBJECTIVE: We aimed to determine the association between C. pneumonia infection and asthma as well as BHR in the adult Thai population. MATERIAL AND METHOD: This nested case-control study retrieved the data from a nation-wide Respiratory Health Survey (2001-02) in the adult population (age 20-44 year) in Thailand. Each subject underwent questionnaire interview, spirometry, bronchoprovocative test, skin prick test for common aeroallergens and venous blood collection. Subjects with BHR (n = 79) including those with asthma (n = 52), were randomly selected as cases. Subjects without BHR or asthma were also randomly selected as the control (n = 137). We used the stored serums for the C. pneumonia serologic assay including IgA, IgG and IgM by microimmunofluorescence (MIF) technique. RESULTS: There is no significant relationship between chronic Chlamydia infection (IgG > or = 1:512 and IgA > or = 1:40) and BHR or asthma. Higher IgM was found in subjects with BHR when compared with the control group (p = 0.04). The IgM titer > or = 1:10 was associated with BHR with borderline significance (odds ratio 1.98; 95% CI 0.98-4.00; p = 0.05). Logistic regression analysis revealed no evidence of confounding effects for age, sex and atopy. However mite allergy seems to be an effect modifier of the relationship between the recent Chlamydia infection and BHR. CONCLUSION: The present study does not support the hypothesis about the association between persistent C. pneumonia infection and chronic asthma. However the recent infection may be related with bronchial hyper-responsiveness particularly in those without allergy to house dust mite.

The prevalence and persistence of human parvovirus B19 infection in thalassemic patients.

Human parvovirus B19 infection was studied in 60 thalassemic patients in Thailand. Seroprevalence, persistence of parvovirus B19 and their genotypes were identified in blood samples. Prevalence of anti-parvovirus B19 IgG and DNA found in thalassemic patients were 38% and 13%, respectively. Anti-parvovirus B19 IgM could be detected in 4% of these positive anti-parvovirus B19 IgG patients. The seroprevalence and parvovirus B19 DNA in patients with a history of blood transfusion were not significantly higher than those without such a history (44% vs. 34% and 20% vs. 9%, respectively). Phylogenetic analysis of NS1 nucleotide sequences of three parvovirus B19 samples revealed that they were parvovirus B19 genotype 1. They showed low genetic diversity from prototype (Au) strain. We concluded that acute and chronic persistent parvovirus B19 infection were found in the thalassemic Thai patients. Chronic persistence of parvovirus B19 infection might play important clinical role in thalassemic patients because of the high prevalence of parvovirus B19 DNA. Blood transfusion had no significant influence to increase the prevalence of parvovirus B19 infection in thalassemic patients.

Specific antibody response of mice after immunization with COS-7 cell derived avian influenza virus (H5N1) recombinant proteins.

To develop avian influenza H5N1 recombinant protein, the hemagglutinin (HA), neuraminidase (NA), matrix (M), and non-structural (NS1) of avian influenza H5N1 isolates from Thailand were engineered to be expressed in prokaryotic (E. coli) and mammalian cell (COS-7) system. The plasmid pBAD-His and pSec-His were used as vectors for these inserted genes. Mice immunized with purified recombinant proteins at concentration 50-250 mug intramuscularly with Alum adjuvant at week 0, week 2, and week 3 showed a good immunogenicity measured by ELISA and neutralization assay. The HA and NS recombinant proteins produced in COS-7 cells can induce specific antibody titer detected by neutralization assay significantly higher than corresponding recombinant proteins produced in E. coli system. The antibody produced in immunized mice could neutralize heterologous avian influenza virus determined by micro-neutralization assay. This study shows that avian influenza virus H5N1 recombinant proteins produced in mammalian cell system were able to induce neutralizing antibody response.

Trends of HIV seropositivity at Siriraj Hospital: 13 year's observation from 1992-2004.

OBJECTIVE: The aim of the present report was to observe the trend of seroprevalence rates of HIV seropositivity for routine services at Siriraj Hospital for 13 years. MATERIAL AND METHOD: The prevalence rate of HIV seropositivity was analyzed in three groups of subjects: 1) patients who attended the hospital with HIV related diseases; 2) pregnant women at first visit to the antenatal care clinic; 3) emigrating workers who have applied for employment in foreign countries. RESULTS: Of the 13 year-observation, HIV seroprevalence rates in the groups of patients, pregnant women and emigrating workers was 10.6% (95%CI 8.9-12.3%), 2.0% (95%CI 1.8-2.2%) and 0.6% (95%CI 0.4-0.8%), respectively. CONCLUSION: The low prevalence of HIV seropositivity in the group of emigrating workers may be due to self selection, whereas the prevalence in pregnant women, which was rather consistent at about 2.0%, may represent the infection rate in the general population. The seroprevalence rate measured in the group of pregnant women demonstrates that Thailand should increase efforts to confine the spread of HIV infection in the community.

Prevalence and incidence of Chlamydia pneumoniae antibodies among the healthy elderly and patients with chronic obstructive pulmonary diseases.

Chlamydia pneumoniae is an obligatory intracellular bacteria which can cause both acute and chronic respiratory tract infection. The significance of chronic and recurrent respiratory infection may be of prime importance in chronic obstructive pulmonary diseases (COPD). The purpose of this study was to determine the prevalence and incidence of C. pneumoniae antibodies in elderly COPD patients compared to a healthy elderly control group. C. pneumoniae antibodies were detected by an enzyme-linked immunosorbent assay in serum samples obtained from 127 elderly COPD patients and a 131 healthy elderly control group. The results showed that the seroprevalence of C. pneumoniae infection as determined by the existence of specific IgG or IgA or IgM antibodies was 96.1% in the COPD patients and 75.6% in the control group (p < 0.01). The prevalence of individual C. pneumoniae IgG, IgA and IgM in elderly COPD vs healthy control was 85.8% vs 66.4%, 85.0% vs 51.1% and 3.9% vs 0%, respectively. The incidence or seroconversion rate of C. pneumoniae antibodies after one year follow-up was found to be 33% in the COPD patients and 67.9% in the control group. High prevalence and incidence of C. pneumoniae antibodies indicates that both acute and chronic C. pneumoniae infection play a role in elderly COPD patients. Therefore, antibiotics of choice for C. pneumoniae infection should probably be considered.

Adenovirus hemorrhagic cystitis in a stem cell transplant patient: the first reported case in Southeast Asia.

Adenovirus (AdV) infections are prevalent in bone marrow transplant patients, usually associated with significant morbidity and mortality. Hemorrhagic cystitis (HC) is a major complication mainly attributed to this virus. The authors report a case of AdV HC in a myelodysplastic patient undergoing peripheral blood stem cell transplantation. The diagnosis was confirmed by positive urine AdV antigen using indirect immunofluorescence assay. The patient gradually improved after adequate hydration, supportive treatment and reduced dose of cyclosporine, and was discharged on the ninth day of hospitalization. To the authors' knowledge, this is the first case of AdV HC in stem cell transplantation in Southeast Asia.

Prevalence of rabies virus and Hantaan virus infections in commensal rodents and shrews trapped in Bangkok.

Five hundred rodents and shrews (Rattus norvegicus: 458, Rattus rattus: 28, Rattus exulans: 5, Mus musculus: 4 and Suncus murine: 5) trapped from the fresh food markets around Bangkok area were investigated for rabies virus and Hantaan virus infections. No rabies viral antigens in the animals' brains were detected by direct immunofluorescence. On the other hand, antibodies to Hantaan virus were demonstrated in the sera of 7 (1.53%) R. norvegicus caught in various markets using a particle agglutination technique. Further determination of the viral genome in rat lung tissue was performed by reverse transcriptase-polymerase chain reaction (RT-PCR) and nested PCR, 3 (0.66%) out of 7 were positive. HindIII and HifI restriction enzyme analyses showed the pattern of the Hantaan virus genome in 2 samples and that of the Seoul virus genome in the other. The results of the present study suggest that rodents from Bangkok's fresh food markets did not carry rabies. Thus, getting rid of rabies in dogs or cats in the Bangkok area may be easier than anticipated because there are no sources of asymptomatic reservoirs. This may result in the low incidence of rabies patients observed in Bangkok. On the contrary, the presence of antibodies and the Hantaan virus genome and Seoul virus genome in R. norvegicus will definitely provide evidence for physicians to be aware of hemorrhagic fever with renal syndrome (HFRS) and other clinical settings of Hantaan/Seoul virus disease in patients with a history of having contact with rats or their excreta.

Seroprevalence of rickettsial infection in commensal rodents and shrews trapped in the Bangkok Metropolitan Area.

Murine typhus and scrub typhus are important human rickettsial diseases in Thailand. Small mammals, including many species of rodents and shrews, serve as the reservoir host of rickettsial diseases. Rickettsia typhi can be transmitted to humans by fleas causing murine typhus, while infection with Orientia tsutsugamushi causing scrub typhus in humans is transmitted by chiggers. The prevalence of rickettsial infection depends on the geographic area. The seroprevalence of antibody to R. typhi and O. tsutsugamushi was studied in commensal rodents and shrews trapped in markets in the Bangkok Metropolitan Area (BMA). R. typhi and O. tsutsugamushi antigen prepared in the yolk sac of embryonated eggs were used to determine the specific antibody in trapped animals' sera by using fluorescein isothiocyanate (FITC)-anti rat immunoglobulins as a second antibody. Antibody to R. typhi was found in 25 (5%) of 500 sera tested and no antibody to O. tsutsugamushi was detected. R. typhi antibody titer ranged from 40-1280 and was found in Rattus norvegicus (4.2%), Rattus rattus (0.4%), Rattus exulans (0.2%), and Mus musculus (0.2%) trapped in 8 of 47 markets in the BMA. R. typhi antibody was commonly found in R. norvegicus. The authors concluded that murine typhus is an important rickettsial disease and R. norvegicus is an important reservoir species of rodents found in markets of the BMA.

Shiga toxin- and enterotoxin-producing Escherichia coli isolated from subjects with bloody and nonbloody diarrhea in Bangkok, Thailand.

A total of 314 stool samples collected from 92 subjects with bloody diarrhea, 119 subjects with non-bloody diarrhea and 103 normal subjects in Bangkok, Thailand, were investigated for the presence of Shiga toxin-producing Escherichia coli (STEC) and enterotoxin-producing E. coli (ETEC) by multiplex PCR assay. Virulence genes and cytotoxic effect to Vero cells of STEC were also determined. STEC (5 isolates) and ETEC (18 isolates) were detected in 3 and 14 subjects, respectively. Among subjects containing ETEC, only one person belonged to normal control group. The detected STEC included two isolates (serotypes O26:H(-) and O111:H(-)) of Shiga toxin type 1 (Stx1-only) STEC from a child with non-bloody diarrhea, two isolates (Stx1-Stx2 STEC and Stx1-only STEC) from an adult with bloody diarrhea, and one isolate of Stx1-Stx2v STEC (O157:H7) from normal child. Only Stx1-Stx2 STEC isolate was found to exhibit toxicity to Vero cells and carry hlyA gene. The intimin encoding gene locus eaeA was not detected in any isolate. These results indicate that most of STEC isolates in Thailand were low virulent.

Respiratory syncytial virus-associated lower respiratory tract infection in under-5-year-old children in a rural community of central Thailand, a population-based study.

The population-based cohort study on the epidemiology of respiratory syncytial virus (RSV)-associated lower respiratory tract infection (LRI) (RSV-LRI) was conducted in Takhli district from November 1998 to February 2001. The incidence of RSV-LRI was 12.6/1,000 child-year and 5.8/ 1,000 child-year during the first and second year, respectively. RSV accounted for 35.8 per cent of all LRI cases during the first year and significantly decreased to 17.5 per cent during the second year. Three-quarters of RSV-LRI occurred among children under 2 years old (76.6% during the first year and 62.2% during the second year). Most of RSV-LRI in both years occurred from July to October. Risk factor for morbidity of RSV infections were age less than or equal to 2 years (OR = 2.38, 95% CI = 1.22-4.67 p = 0.009) and sleeping with more than 3 persons in the patient's bedroom (OR = 2.92,95% CI = 1.42-6.00, p = 0.002). Most RSV-LRI (63.9%) were clinically diagnosed as having pneumonia. No RSV-LRI deaths were detected. During the first year, RSV subtype B was predominate, in contrast to the second year when subtype A was more predominate. Further research to determine the annual change in subtype of RSV-LRI and correlation of severity of disease with specific subtypes needs to conducted in order to prepare for the future introduction of a vaccine.

Acute viral lower respiratory infections in children in a rural community in Thailand.

The present study was conducted as a population based cohort in a rural community of Amphoe Takhli, Nakhon Sawan province for the determination of the prevalence of acute viral lower respiratory infection (ALRI) in pediatric cases under 5 years of age from November 1998 to February 2001. There were 472 ALRI episodes during the study period; and there were 5 cases who contracted ALRI twice. The etiologic agents were determined by indirect immunofluorescence (IIF) test using specific monoclonal antibodies for the staining of exfoliated cells in nasopharyngeal aspirate (NPA) samples. The slides of fixed cells were prepared by Takhli Hospital and posted in ambient temperature to the Virology Laboratory, Siriraj Hospital where they were stained and examined. Among 472 episodes of ALRI, 170 (36.0%) viral agents were found. Viral agents were associated with 41.4 per cent of all pneumonic cases. Respiratory syncytial virus (RSV) was the most common virus observed in the present study; and it was also the most common virus associated with pneumonia and bronchitis. RSV subgrouping was performed directly in NPA samples by IIF test using a panel of subgroup specific monoclonal antibodies. RSV subgroup B predominated over subgroup A in the first study year, and it was vice versa in the second year. Overall, more cases of subgroup B were found which was in contrast to what the authors had reported in the previous study. Prevalence of RSV was seasonal dependent, the epidemic was seen during the rainy season with peaks in August or September of each year. As the method of viral identification was limited to IIF only, therefore, fewer viruses were detected. Parainfluenza viruses were detected as the second most common viral agent, the viruses spread during early summer with peaks in February or March of each year. However, its association with croup could not be demonstrated which may be due to the insensitivity of IIF in the diagnosis of non-RSV infection. Nevertheless, in terms of feasibility to investigate the disease in a rural area, IIF is economic, convenient and rapid; and gives enough information for the nationwide plan of a health care development system.