Urinary tract infection in male general practice patients: uropathogens and antibiotic susceptibility.

OBJECTIVES: To evaluate uropathogens and their antibiotic susceptibility in male general practitioner (GP) patients presenting with an uncomplicated urinary tract infection (UTI). MATERIAL AND METHODS: A population-based study was conducted among males, 18 years and older, general practice patients, who had symptoms indicative of an uncomplicated UTI. A UTI was defined as >/=10(3) colony-forming units/mL (CFU/mL). The etiology of the infection, antimicrobial susceptibility, and treatment strategies used by the GP were determined. RESULTS: Escherichia coli was most frequently isolated (48%), followed by other enterobacteriaceae (24%) and enterococci (9%). The etiology of infection was age-dependent; E. coli was more frequently isolated in younger patients and Pseudomonas aeruginosa in the elderly. The overall susceptibility rates were low for amoxicillin (63%) and trimethoprim (70%), and high for fluoroquinolones (91%) and amoxicillin-clavulanic acid (90%), which is similar to susceptibility rates in females with UTIs from the same population. Antibiotics were prescribed to 59% of the males with symptoms of UTI. Fluoroquinolones were given to 33% of the patients and trimethoprim-sulfamethoxazole to 24%. No difference in antibiotic prescription, nor in duration of therapy, was found between the different age groups. CONCLUSIONS: In the male presenting with complaints of an acute uncomplicated UTI at the GP, E. coli, followed by other Gram-negative bacteria were the most frequently isolated uropathogens. Susceptibility rates in uncomplicated male and female UTIs were similar, indicating that data from UTI susceptibility studies in females from the same geographic region can be useful in the choice of empirical therapy in males.

Evaluation of the nitrite and leukocyte esterase activity tests for the diagnosis of acute symptomatic urinary tract infection in men.

For 422 male patients with symptoms indicative of a urinary tract infection, nitrite and leukocyte esterase activity dipstick test results were compared with results of culture of urine samples. The positive predictive value of a positive nitrite test result was 96%. Addition of results of the leukocyte esterase test did not improve the diagnostic accuracy of the nitrite test.

Urinary tract infections in general practice patients: diagnostic tests versus bacteriological culture.

OBJECTIVES: Urinary tract infections (UTIs) are common bacterial infections encountered in general practice. For the optimal treatment the general practitioner (GP) should rely on the results of diagnostic tests and recent antimicrobial susceptibility of uropathogens. PATIENTS AND METHODS: In total 1993 female patients (11-70 years) with complaints of an acute uncomplicated UTI were included. The performance characteristics of the diagnostic tests used were determined and compared with the antibiotic prescription rate. The antibiotic therapy (agent and duration), the uropathogens and the antibiotic susceptibility of Escherichia coli were determined for each age group. RESULTS: The positive predictive value (PPV) (96%) and the specificity (94%) of the nitrite test were high for all samples. A negative nitrite with a positive leucocyte-esterase (LE) test showed a high PPV (79%) and sensitivity (82%). When both nitrite and LE tests were negative approximately 50% of the samples were culture positive. Of the patients, 94% of those with a positive nitrite test and 71% of those with a negative nitrite and positive LE test were prescribed antibiotics, mostly nitrofurantoin and trimethoprim. Nitrofurantoin prescriptions decreased and those of fluoroquinolones increased with increasing age. Nitrofurantoin was equally prescribed for 3-7 days in all patients. Trimethoprim was mostly prescribed for 3 days in patients aged 21-50 years and for 5 days in the other patients. E. coli, the uropathogen mostly isolated, decreased in frequency with increasing age. Proteus mirabilis was found more in the oldest patients and Staphylococcus saprophyticus in the younger patients. The antimicrobial susceptibility of E. coli was not age related. The lowest percentages were found for amoxicillin (67%) and trimethoprim (77%). Fluoroquinolone resistance was emerging in the older patients. CONCLUSIONS: For female patients with symptoms of an acute uncomplicated UTI a positive nitrite test or a negative nitrite test with a positive LE test confirmed UTI whereas a negative nitrite together with a negative LE test did not rule out infection. For empirical treatment GPs should take into account the changing aetiology with increasing age. Prudent use of antibiotics in general and more specifically fluoroquinolones remains recommended. As trimethoprim resistance reached 20% it might be advisable to no longer use it as therapy of first choice for acute uncomplicated UTIs in The Netherlands.

Antibiotic treatment and resistance of unselected uropathogens in the elderly.

A population-based study was conducted among women over the age of 70 years with complaints of uncomplicated urinary tract infections (UTIs). The positive predictive value of the nitrite test alone or in combination with the leukocyte esterase test ranged between 83% and 99%. The nitrofurantoin prescription rate decreased whereas fluoroquinolone and amoxicillin/clavulanic acid prescriptions increased with increasing age. The aetiology of infection was age-dependent. Escherichia coli was the most commonly isolated uropathogen, followed by Proteus mirabilis and Klebsiella pneumoniae. For these uropathogens, the lowest susceptibility percentages were found for amoxicillin, trimethoprim and co-trimoxazole. As trimethoprim susceptibility reached approximately 75%, it may be advisable not to use this as a first-choice agent in the treatment of uncomplicated UTIs in the elderly.

[The influenza season 2004/'05 in the Netherlands with the largest epidemic of the last 5 years caused by the virus variant A/California and the composition of the vaccine for the season 2005/'06]. / Het influenzaseizoen 2004/'05 in Nederland met de grootste epidemie van de laatste 5 jaar, door virusvariant A/California, en de vaccinsamenstelling voor het seizoen 2005/'06.

In the Netherlands, the influenza epidemic of the 2004/'05 season started late. The background value of 3 cases of an influenza-like illness per 10,000 inhabitants per week was exceeded from week 1 until week 14 of 2005. The magnitude of the epidemic was the largest of the last 5 years, namely 104 per 10,000 inhabitants. As usual, the epidemic was caused mainly by influenza-A viruses of subtype H3N2 and to a lesser degree by A/H1N1 and B viruses. The H3N2-virus isolates belonged to the newly emerged variant A/California/7/04, which deviated slightly from the vaccine strain used for the 2004/'05 season. The influenza-B and H1N1 viruses matched the corresponding vaccine viruses well. For the 2005/'06 season, the World Health Organization has recommended the following vaccine composition: A/California/7/04 (H3N2), A/New Caledonia/20/99 (HiNI), and B/Shanghai/361/02.

Erythromycin resistance in the commensal throat flora of patients visiting the general practitioner: a reservoir for resistance genes for potential pathogenic bacteria.

The prevalence and mechanism of erythromycin resistance in commensal throat streptococci was determined from October 2000 until December 2002 as part of an ongoing study of the NIVEL in general practice patients (N=678). Resistance prevalence for 1mg/L and 16 mg/L erythromycin was 57% and 20%, respectively. The percentage of total commensal flora resistant within each patient ranged from 1% to 100% (median, 1%). mefA was predominantly found among isolates on the 1mg/L plates, and ermB was found in 64% of the isolates on the 16 mg/L plates. Erythromycin resistance was transferred from a commensal isolate to Streptococcus pneumoniae with a frequency of 1 x 10(-9). Commensal streptococci of general practice patients in The Netherlands form a large reservoir of transferable erythromycin resistance (genes) for potential pathogenic microorganisms.

[The 2003/2004 influenza season in the Netherlands with a limited epidemic of the virus variant A/Fujian, and the vaccine composition for the 2004/2005 season]. / Het influenzaseizoen 2003/'04 in Nederland met een beperkte epidemie door de virusvariant A/Fujian, en de vaccinsamenstelling voor het seizoen 2004/'05.

In contrast to the three previous influenza seasons, the influenza epidemic of the 2003/2004 season started early in week 49 of 2003. The epidemic was predominantly caused by influenza-A viruses of the H3N2 subtype. All isolated influenza-A viruses were antigenically related to influenza virus A/Fujian/411/02, which was already detected in the influenza season 2002/2003 and that deviated from the vaccine-reference strain A/Moscow/10/99 to a certain extent. The magnitude of the epidemic was limited despite the fact that it was caused by influenza-A H3N2-virus-drift variants. Immunity caused by natural infection with influenza viruses during previous seasons or vaccination has possibly provided sufficient cross protection against these new H3N2-drift variant. No influenza-A viruses of the H1N1 or H1N2 subtypes were detected in the influenza season 2003/2004. Only a small number of influenza-B viruses were isolated, which all belonged to the B/Yamagata/16/88 lineage, which was temporarily replaced by the B/Victoria2/87 lineage in the previous influenza season. On the basis of epidemiological and serological data the World Health Organization has recommended the following vaccine composition for the 2004/2005 influenza season: A/Fujian/411/02 (H3N2), A/New Caledonia/20/99 (H1N1) and B/Shanghai/361/02.

Are influenza surveillance data useful for mapping presentations?

Geographical information system (GIS) based on mappings of influenza data are rare (http://www.b3e.jussieu.fr.80/sentiweb/fr) and influenza data are commonly aggregated for rather large areas (http://www.eiss.org, http://oms2b3e.jussieu.fr/FluNet). The most limiting factors for the use of morbidity-data from practices in GIS-based mappings are differences which are not related to morbidity. These differences may be due to consultation behaviour, interpretation of the case definition, age distribution of patients and other reasons. In order to reduce the impact of these non-morbidity related differences on the interpretation, the data of many practices are usually pooled and consequently rather large areas are presented. Extracting and harmonising the signals for increased morbidity from practices is a presupposition for mapping with a sufficient geographical resolution. The possibility to harmonise by reducing those confounding differences on a practice level is investigated. Different harmonisation methods were applied to data from Germany where acute respiratory infections (ARI) per consultations are registered and from The Netherlands were influenza like illnesses (ILI) per population are registered. The harmonisation of the indices between countries was achieved by scaling them in relation to the level of the index representative for the peak activity during a usual influenza epidemic. The Kriging method is applied as a means of spatial prediction for the influenza data. The preliminary results are discussed with respect to resulting mappings.

[The 2002/2003 influenza season in the Netherlands and the vaccine composition for the 2003/2004 season]. / Het influenzaseizoen 2002/'03 in Nederland en de vaccinsamenstelling voor het seizoen 2003/'04.

As in the 2000/2001 and 2001/2002 seasons, the influenza epidemic in the 2002/2003 season started late (week 7 of 2003) and was only moderate in size. Influenza A (H3N2) and B viruses were detected in equal numbers among patients of general practitioners and these two viruses were therefore equally responsible for the epidemic. However, H3N2 viruses dominated isolates taken from hospitals. In haemagglutination-inhibition (HI) assays most of the H3N2 viruses proved highly reactive with antiserum to the vaccine-reference strain A/Moscow/10/99. This was also true for a number of isolates, including those obtained from nursing home residents, closely related to the reference strain A/Finland/170/03. However, an estimated 4% of the H3N2 isolates belonged to the variant A/Fujian/411/02 from China, which constituted the majority of the H3N2 viruses isolated in Europe in the later phase of the season. This variant reacted poorly with antiserum to A/Moscow/10/99. In H1 tests all influenza A(H1N1)-virus isolates and all B-virus isolates were closelyrelated to the corresponding vaccine-reference strains. Taking this data into consideration, the World Health Organization has advised the same vaccine composition for the 2003/2004 season as for the 2002/2003 season, namely: A/Moscow/10/99 (H3N2), A/New Caledonia/20/99 (H1N1) and B/Hong Kong/330/01. There is the possibility of a mismatch occurring between the H3N2-vaccine strain and the circulating H3N2 viruses in the coming influenza season. In March and April 2003 there was an outbreak of influenza-A (H7N7) fowl plague in the Netherlands. A special monitoring survey revealed that 91 people who had handled infected poultry became infected with the H7N7 virus. One of these later died as a result of this. None of the avian and human H7N7-virus isolates examined contained human or porcine influenza-A virus genes.

[The 2001/2002 influenza season and the vaccine composition for the 2002/2003 season]. / Het influenzaseizoen 2001/'02 en de vaccinsamenstelling voor het seizoen 2002/'03.

The epidemic in the influenza season 2001/2002 was of moderate activity just like in 2000/2001. The influenza epidemic started in week 2 of 2002 when the clinical influenza activity reported by the general practitioner network of the Netherlands Institute of Primary Health Care (NIVEL) increased. This was caused by influenza A viruses of the H3N2 subtype in particular. All influenza A viruses of this subtype were closely related to the vaccine strain for this subtype, A/Moscow/10/99. Influenza B viruses and influenza A/H1 viruses isolated this season had surprising features. The influenza B viruses originated from two lineages. Viruses of the B/Yamagata/16/88 lineage have been circulating for more than twelve years. The vaccine reference strain B/Sichuan/379/99 belongs to this lineage. The B/Victoria/2/87 lineage reappeared again after an absence in Europe of more than ten years and accounted for 50% of the influenza B viruses that were isolated in the Netherlands. Therefore the vaccine will have provided only partial protection against influenza B. The only influenza A/H1 virus that was isolated appeared to be of a new subtype H1N2. The H1 hemagglutinin of this virus was closely related to that of the vaccine strain A/New Caledonia/20/99. The N2 neuraminidase originated from recent human influenza A/H3N2 viruses. Therefore the vaccine probably provided good protection against the new H1N2 subtype. Based in part on these data, the World Health Organization has advised that the vaccines for the season 2002/2003 should contain the following or comparable influenza-virus strains: A/Moscow/10/99 (H3N2), A/New Caledonia/20/99 (H1N1) and B/Hong Kong/330/01, the latter being an influenza B virus of the B/Victoria/2/87 lineage.

Unexplained severe chronic pain in general practice.

The aim of this study was to estimate the prevalence of unexplained severe chronic pain (USCP) in general practice and to report medical as well as psychological descriptions of patients suffering from this condition.A total of 45 GPs in 35 different practices included patients throughout the year 1996. Patients were included according to the following criteria: between 18 and 75 years of age; pain which had lasted at least 6 months; pain is the most prominent aspect in the clinical presentation; pain is serious enough to justify clinical attention; pain has led to obvious discomfort and disability in daily life for at least for 1 month. Medical aspects were measured with the IASP taxonomy while psychological aspects were derived from the MPI. The overall prevalence of USCP was 7.91 per 1000 enlisted patients. Estimates ranged between 1.87 in the youngest age group and 13.50 in the 55-59 age category. The lower back and lower limbs were most frequently affected and 31% of the patients had pain in more than three major body sites. Pain was most frequently associated by the musculoskeletal system and most often (nearly) continuous. Mean severity of current pain was 3.7 on a scale from 0 (indicating no pain) to 6 (indicating a lot of pain). Mean rating of 'average pain in the last week' was 4.1. Regarding the psychosocial and behavioural aspects of pain, 27% of the patients could be described as perceiving severe pain while gaining social support for it. Fourteen per cent felt in the category 'pain combined with affective and relational distress' and 10% was classified as 'coping well with pain intensities lower than those of the other groups'. The other half of the patients were on average or not classifiable on these aspects. Unexplained severe chronic pain lasting more than 6 months had on overall prevalence of 7.91 per 1000 enlisted patients, ranging from 1.87 in the youngest to 13.50 in the oldest patients in these 35 general practices in The Netherlands. Our prevalence estimate of USCP is low compared to other studies on chronic pain. Probably for three reasons: Firstly, our study was confined to unexplained pain and not all chronic pain. Secondly, our inclusion criteria focused the attention of very severe chronic pain patients, and thirdly, we have defined 'chronic' as more than 6 months, while others have been using shorter time spans.

Sensor, a population-based cohort study on gastroenteritis in the Netherlands: incidence and etiology.

A prospective population-based cohort study with a nested case-control study was conducted to estimate the incidence of gastroenteritis and the associated pathogens in the general Dutch population. Follow-up of two consecutive cohorts was performed by weekly reporting cards from December 1998 to December 1999. Cases and controls in the case-control study supplied a questionnaire and stool samples. The standardized gastroenteritis incidence was 283 per 1,000 person-years. The incidence rose with increasing level of education and was higher for persons with a history of diarrhea and for young children. Bacterial pathogens accounted for 5% of cases, bacterial toxins for 9%, parasites for 6%, and viral pathogens for 21%, with Norwalk-like virus (NLV) as the leading pathogen in 11% of cases. The gastroenteritis incidence was higher than that reported for England, but lower than for the United States. In community cases, viral pathogens are the leading cause of gastroenteritis, with NLV being the number one cause of illness in all age groups but one. In many countries, preventive measures are implemented to decrease bacterial infections. However, additional prevention of viral infections, especially NLV, might significantly decrease the number of gastroenteritis cases in the community.

[2000/01 influenza season and the vaccine composition for the season 2001/'02]. / Het influenzaseizoen 2000/'01 en de vaccinsamenstelling voor het seizoen 2001/'02.

In the 2000/01 season, the size of the influenza epidemic in the Netherlands was exceptionally small. Since the start of the Continuous Morbidity Registration of the Netherlands Institute of Primary Health Care (NIVEL) in 1970, the peak incidence of influenza-like illnesses has never been so low. The aetiology of the epidemic was also unusual. Most remarkable was the relatively extensive circulation of subtype H1N1 and the low activity of subtype H3N2. The epidemic started in week 1 of 2001 and ended in week 8. The antigenic properties of the influenza A (H1N1) viruses closely resembled those of the vaccine strain A/New Caledonia/20/99. This new variant of subtype H1N1 was first isolated in Asia in 1995 and was only (sporadically) detected in the Netherlands in the 1999/2000 season. Phylogenetic analysis showed that these viruses represent a new line of subtype H1N1. Following the influenza-activity caused by H1N1 viruses in the 2000/01 season, a small number of B and H3N2 viruses were also isolated up to week 19. Antigenically, these viruses were identical to those obtained in the previous years. On the basis of the antigenetic analyses presented, it can be concluded that the vaccine provided good protection against the circulating influenza viruses in the 2000/01 season. The World Health Organization recommends that influenza vaccines intended for use in the 2001/02 season of the northern hemisphere should contain the following, or antigenically similar, strains: A/Moscow/10/99 (H3N2), A/New Caledonia/20/99 (H1N1), and B/Sichuan/379/99.

Gastroenteritis in sentinel general practices,The Netherlands.

From 1996 to 1999, the incidence of gastroenteritis in general practices and the role of a broad range of pathogens in the Netherlands were studied. All patients with gastroenteritis who had visited a general practitioner were reported. All patients who had visited a general practitioner for gastroenteritis (cases) and an equal number of patients visiting for nongastrointestinal symptoms (controls) were invited to participate in a case-control study. The incidence of gastroenteritis was 79.7 per 10,000 person years. Campylobacter was detected most frequently (10% of cases), followed by Giardia lamblia (5%), rotavirus (5%), Norwalk-like viruses (5%) and Salmonella (4%). Our study found that in the Netherlands (population 15.6 million), an estimated 128,000 persons each year consult their general practitioner for gastroenteritis, slightly less than in a comparable study in 1992 to 1993. A pathogen could be detected in almost 40% of patients (bacteria 16%, viruses 15%, parasites 8%).

Results of molecular detection of Mycoplasma pneumoniae among patients with acute respiratory infection and in their household contacts reveals children as human reservoirs.

During a 30-month prospective study in The Netherlands, the distribution of Mycoplasma pneumoniae and respiratory viruses among 1172 patients with acute respiratory infection (ARI) who were treated in the outpatient general practitioner setting was studied. M. pneumoniae, as detected by polymerase chain reaction analysis, was present in 39 (3.3%) patients. The infection rate was similar in all age groups. Nose and throat samples collected from 79 household contacts of M. pneumoniae-positive index patients revealed M. pneumoniae in 12 (15%) cases. The frequency of M. pneumoniae among household contacts of index patients treated with appropriate antibiotics and untreated index patients was similar. Nine of the 12 M. pneumoniae-positive household contacts were <16 years old (P=.02), and 4 (44%) of them did not develop ARI. Apparently, children are a relevant reservoir for M. pneumoniae.

A comparison of gastroenteritis in a general practice-based study and a community-based study.

We compared gastroenteritis cases that consulted a general practitioner (GP) with those who did not in a community-based study and also with those in a GP-based study. We aimed to identify factors associated with consultation, and with inclusion of cases by GPs, and secondly to study the effects on the frequency of detection of pathogens. Furthermore, we estimated the under-ascertainment by GPs. Both studies were performed in The Netherlands in the same population in an overlapping time-period. Overall, 5% of community cases consulted a GP. Cases who consulted suffered from more severe episodes than non-consulting cases. Inclusion of cases by GPs, instead of a study team, caused a selection of more severe cases with more chronic symptoms. When extrapolating data from GP-based studies, it should be taken into account that, in general practice, gastroenteritis due to bacteria and Giardia lamblia is a relatively large proportion of that in the community and gastroenteritis due to Norwalk-like viruses is a relatively small proportion. The incidence of gastroenteritis in general practices was estimated between 14 and 35 per 1000 person years.

Hormone replacement therapy: changes in frequency and type of prescription by Dutch GPs during the last decade of the millennium.

OBJECTIVE: The present study was conducted in order to determine the change of frequency and type of hormone replacement therapy (HRT) regimen newly prescribed by Dutch GPs. METHODS: A comparison was made of two data sets (multi-stage random samples) collected in 1987/88 and from 1995 to 1998 concerning women 40 years and older who were newly prescribed HRT. RESULTS: Compared with 1987/88, 50% more patients were newly prescribed HRT in 1998 (2.0 in 1987/88 and 3.0 in 1998 per 1000 registered women, P < 0.01). The age distribution remained about the same, with a peak between 50 and 54 years in each year of registration. Unopposed oestrogens (including plasters) were prescribed less frequently (1.3 per thousand in 1987/88 versus 0.7 per thousand in 1998, P < 0.001), and combinations of oestrogen and progestogen more frequently in 1998 (0. 2 per thousand in 1987/88 versus 1.8 per thousand in 1998, P < 0. 01). Sequential therapy was prescribed slightly more frequently than continuous therapy (65% sequential therapy in 1995; 55% in 1998). The most frequent reason for starting HRT in 1995-1998 was climacteric symptoms (89-98%), followed by osteoporosis prevention (16-28%) and early menopause (13-25%). Rarely were preventive goals the only reason (6%) for prescribing HRT. CONCLUSIONS: The number of HRT prescriptions increased by 50% over the last decade of the millennium. The age distribution remained the same. There was a tendency to shift from prescribing unopposed oestrogens to combinations of oestrogens and progestogens. Alleviation of climacteric symptoms was the main reason for prescribing HRT throughout the registration period. Prescription of HRT for prevention of osteoporosis and/or cardiovascular disease has so far not been adopted on a large scale by Dutch GPs.

[Influenza season 1999/2000 and vaccine composition for the season 2000/01]. / Het influenzaseizoen 1999/2000 en de vaccinsamenstelling voor het seizoen 2000/'01.

The first signs of influenza activity in the Netherlands during the 1999/2000 influenza season were the isolation of an influenza A (H3N2) virus in week 40 and of two more in week 43 of 1999. From week 50 onwards, a strong increase of the clinical influenza activity was observed which reached its peak in weeks 1 and 2 of 2000 and then rapidly declined. The clinical influenza activity was associated with the isolation of predominantly influenza A (H3N2) viruses. Near the end of the epidemic, influenza A (H1N1) and influenza B viruses were isolated sporadically. The antigenic properties of the influenza A (H3N2) viruses resembled those of the epidemic strains isolated in the previous season and the vaccine strain A/Sydney/5/97. This influenza season, influenza B viruses did not play a significant role and they matched the vaccine strain B/Yamanashi/166/98. In addition, a small number of influenza A (H1N1) viruses were isolated. Some of these viruses resembled the old variant of influenza A (H1N1) viruses, A/Bayern/7/95, whilst others showed a close antigenic relationship with the vaccine strain recommended for the next influenza season, A/New Caledonia/20/99. For the influenza season 2000/'01, it is recommended by the World Health Organization that the vaccines contain the following (or similar) virus strains: A/Moscow/10/99 (H3N2), A/New Caledonia/20/99 (H1N1) and B/Beijing/184/93.

Population estimates of persons presenting to general practitioners with influenza-like illness, 1987-96: a study of the demography of influenza-like illness in sentinel practice networks in England and Wales, and in The Netherlands.

Incidence data by age of new episodes of influenza-like illness reported by sentinel general practice networks in England and Wales and in The Netherlands over a 10-year period were examined to provide estimates of the consulting population during influenza epidemic periods. Baseline levels of recording in each age group were calculated from weeks in which influenza viruses were not circulating and the excess over baseline calculated to provide the population estimates during influenza epidemics. Influenza A/H3N2 epidemics were associated with higher population estimates for consultations than influenza B, especially in the age groups 0-4 and 65 years and over. In the intervening age groups, population estimates were more consistent regardless of the virus type. Both networks reported simultaneous peaking of incidence rates in all of the age groups. There were substantial increases in the number of persons reporting other respiratory illnesses during influenza epidemics. Population estimates of the consulting population provide the only secure basis for which health services resource utilization during influenza epidemics can be estimated.