Toxoplasmosis hospitalizations in the United States, 2008, and trends, 1993-2008.

BACKGROUND: Toxoplasmosis-related hospitalizations often occur in persons with human immunodeficiency virus (HIV) infection and other causes of immunosuppression. METHODS: Using the National Inpatient Sample (NIS) from the Healthcare Cost and Utilization Project, we examined trends in toxoplasmosis-related hospitalizations by HIV infection status from 1993 through 2008, and rates by sex and race or ethnicity in 2008. The NIS is designed to represent a 20% sample of US community hospitals and currently includes information on up to 8 million discharges per year from ∼1000 hospitals. We used International Classification of Diseases, Ninth Revision, Clinical Modification codes 130-130.9 for toxoplasmosis and 042-044/795.8/795.71/V08 for HIV infection. RESULTS: Estimated HIV-associated toxoplasmosis hospitalizations increased from 9395 in 1993 to 10583 in 1995 (P = .0002), then dropped to 3643 in 2001 (P < .0001), with similar levels thereafter. The rate of HIV-associated toxoplasmosis hospitalizations among all HIV-related hospitalizations decreased from 3.33% in 1993 to 1.25% in 2008 (P < .0001). Estimated non-HIV-associated toxoplasmosis hospitalizations were less variable from 1993 to 2008 (range, 386-819; 0.0020% in 1993, 0.0015% in 2008). In 2008, the rates of both HIV- and non-HIV-associated toxoplasmosis hospitalizations were higher in Hispanic persons than in white persons. CONCLUSIONS: HIV-associated toxoplasmosis hospitalizations dropped markedly after 1995 when highly active antiretroviral therapy was introduced; however, hospitalizations decreased relatively little after 2000, suggesting late diagnosis of some HIV-infected persons or antiretroviral therapy failure. Non-HIV-associated toxoplasmosis hospitalizations have been more stable. The rates of toxoplasmosis-related hospitalizations varied markedly among racial and ethnic groups.

Routine delivery of artemisinin-based combination treatment at fixed health facilities reduces malaria prevalence in Tanzania: an observational study.

BACKGROUND: Artemisinin-based combination therapy (ACT) has been promoted as a means to reduce malaria transmission due to their ability to kill both asexual blood stages of malaria parasites, which sustain infections over long periods and the immature derived sexual stages responsible for infecting mosquitoes and onward transmission. Early studies reported a temporal association between ACT introduction and reduced malaria transmission in a number of ecological settings. However, these reports have come from areas with low to moderate malaria transmission, been confounded by the presence of other interventions or environmental changes that may have reduced malaria transmission, and have not included a comparison group without ACT. This report presents results from the first large-scale observational study to assess the impact of case management with ACT on population-level measures of malaria endemicity in an area with intense transmission where the benefits of effective infection clearance might be compromised by frequent and repeated re-infection. METHODS: A pre-post observational study with a non-randomized comparison group was conducted at two sites in Tanzania. Both sites used sulphadoxine-pyrimethamine (SP) monotherapy as a first-line anti-malarial from mid-2001 through 2002. In 2003, the ACT, artesunate (AS) co-administered with SP (AS + SP), was introduced in all fixed health facilities in the intervention site, including both public and registered non-governmental facilities. Population-level prevalence of Plasmodium falciparum asexual parasitaemia and gametocytaemia were assessed using light microscopy from samples collected during representative household surveys in 2001, 2002, 2004, 2005 and 2006. FINDINGS: Among 37,309 observations included in the analysis, annual asexual parasitaemia prevalence in persons of all ages ranged from 11% to 28% and gametocytaemia prevalence ranged from <1% to 2% between the two sites and across the five survey years. A multivariable logistic regression model was fitted to adjust for age, socioeconomic status, bed net use and rainfall. In the presence of consistently high coverage and efficacy of SP monotherapy and AS + SP in the comparison and intervention areas, the introduction of ACT in the intervention site was associated with a modest reduction in the adjusted asexual parasitaemia prevalence of 5 percentage-points or 23% (p < 0.0001) relative to the comparison site. Gametocytaemia prevalence did not differ significantly (p = 0.30). INTERPRETATION: The introduction of ACT at fixed health facilities only modestly reduced asexual parasitaemia prevalence. ACT is effective for treatment of uncomplicated malaria and should have substantial public health impact on morbidity and mortality, but is unlikely to reduce malaria transmission substantially in much of sub-Saharan Africa where individuals are rapidly re-infected.

Causes of outbreaks associated with drinking water in the United States from 1971 to 2006.

Since 1971, the CDC, EPA, and Council of State and Territorial Epidemiologists (CSTE) have maintained the collaborative national Waterborne Disease and Outbreak Surveillance System (WBDOSS) to document waterborne disease outbreaks (WBDOs) reported by local, state, and territorial health departments. WBDOs were recently reclassified to better characterize water system deficiencies and risk factors; data were analyzed for trends in outbreak occurrence, etiologies, and deficiencies during 1971 to 2006. A total of 833 WBDOs, 577,991 cases of illness, and 106 deaths were reported during 1971 to 2006. Trends of public health significance include (i) a decrease in the number of reported outbreaks over time and in the annual proportion of outbreaks reported in public water systems, (ii) an increase in the annual proportion of outbreaks reported in individual water systems and in the proportion of outbreaks associated with premise plumbing deficiencies in public water systems, (iii) no change in the annual proportion of outbreaks associated with distribution system deficiencies or the use of untreated and improperly treated groundwater in public water systems, and (iv) the increasing importance of Legionella since its inclusion in WBDOSS in 2001. Data from WBDOSS have helped inform public health and regulatory responses. Additional resources for waterborne disease surveillance and outbreak detection are essential to improve our ability to monitor, detect, and prevent waterborne disease in the United States.

Effects of source water quality on chlorine inactivation of adenovirus, coxsackievirus, echovirus, and murine norovirus.

More information is needed on the disinfection efficacy of chlorine for viruses in source water. In this study, chlorine disinfection efficacy was investigated for USEPA Contaminant Candidate List viruses coxsackievirus B5 (CVB5), echovirus 1 (E1), murine norovirus (MNV), and human adenovirus 2 (HAdV2) in one untreated groundwater source and two partially treated surface waters. Disinfection experiments using pH 7 and 8 source water were carried out in duplicate, using 0.2 and 1 mg/liter free chlorine at 5 and 15 degrees C. The efficiency factor Hom (EFH) model was used to calculate disinfectant concentration x contact time (CT) values (mg x min/liter) required to achieve 2-, 3-, and 4-log(10) reductions in viral titers. In all water types, chlorine disinfection was most effective for MNV, with 3-log(10) CT values at 5 degrees C ranging from < or = 0.020 to 0.034. Chlorine disinfection was least effective for CVB5 in all water types, with 3-log(10) CT values at 5 degrees C ranging from 2.3 to 7.9. Overall, disinfection proceeded faster at 15 degrees C and pH 7 for all water types. Inactivation of the study viruses was significantly different between water types, but no single source water had consistently different inactivation rates than another. CT values for CVB5 in one type of source water exceeded the recommended CT values set forth by USEPA's Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems using Surface Water Sources. The results of this study demonstrate that water quality plays a substantial role in the inactivation of viruses and should be considered when developing chlorination plans.

Ownership and usage of insecticide-treated bed nets after free distribution via a voucher system in two provinces of Mozambique.

BACKGROUND: Insecticide-treated bed nets (ITNs) are an efficacious intervention for malaria prevention. During a national immunization campaign in Mozambique, vouchers, which were to be redeemed at a later date for free ITNs, were distributed in Manica and Sofala provinces. A survey to evaluate ITN ownership and usage post-campaign was conducted. METHODS: Four districts in each province and four enumeration areas (EAs) in each district were selected using probability proportional to size. Within each EA, 32 households (HHs) were selected using a simple random sample. Interviews to assess ownership and usage were conducted in each of the selected HHs using personal digital assistants. RESULTS: Valid interviews were completed for 947 (92.5%) (440 in Manica and 507 in Sofala) of the 1,024 selected HHs. Among participating HHs, 65.0% in Manica and 63.1% in Sofala reported that at least one child under five years of age slept in the house the previous night. HH ownership of at least one bed net of any kind was 20.6% (95% confidence interval [CI]: 7.9%-43.6%) and 35.6% (95% CI: 27.8%-44.3%) pre-campaign; and 55.1% (95% CI: 43.6%-66.1%) and 59.6 (95% CI: 42.4%-74.7%) post-campaign in Manica and Sofala, respectively. Post-campaign HH ownership of at least one ITN was 50.2% (95% CI: 41.8%-58.5%) for both provinces combined. In addition, 60.3% (95% CI: 50.6%-69.2%) of children under five years of age slept under an ITN the previous night. CONCLUSIONS: This ITN distribution increased bed net ownership and usage rates. Integration of ITN distribution with immunization campaigns presents an opportunity for reaching malaria control targets and should continue to be considered.

Development and evaluation of porcine cysticercosis QuickELISA in Triturus EIA analyzer.

We evaluated three diagnostic antigens (recombinant GP50, recombinant T24H, and synthetic Ts18var1) for cysticercosis and found that all three performed well in detecting cysticercosis in humans and pigs in several assay formats. These antigens were adapted to a new antibody detection format (QuickELISA). With one single incubation step which involves all reactants except the enzyme substrate, the QuickELISA is particularly suited for automation. We formatted the QuickELISA for the Triturus EIA analyzer for testing large numbers of samples. We found that in QuickELISA formats rGP50 and rT24H have better sensitivity and specificity than sTs18var1 for detecting porcine cysticercosis.

Risk factors for Toxoplasma gondii infection in the United States.

BACKGROUND: Toxoplasmosis can cause severe ocular and neurological disease. We sought to determine risk factors for Toxoplasma gondii infection in the United States. METHODS: We conducted a case-control study of adults recently infected with T. gondii. Case patients were selected from the Palo Alto Medical Foundation Toxoplasma Serology Laboratory from August 2002 through May 2007; control patients were randomly selected from among T. gondii-seronegative persons. Data were obtained from serological testing and patient questionnaires. RESULTS: We evaluated 148 case patients with recent T. gondii infection and 413 control patients. In multivariate analysis, an elevated risk of recent T. gondii infection was associated with the following factors: eating raw ground beef (adjusted odds ratio [aOR], 6.67; 95% confidence limits [CLs], 2.09, 21.24; attributable risk [AR], 7%); eating rare lamb (aOR, 8.39; 95% CLs, 3.68, 19.16; AR, 20%); eating locally produced cured, dried, or smoked meat (aOR, 1.97; 95% CLs, 1.18, 3.28; AR, 22%); working with meat (aOR, 3.15; 95% CLs, 1.09, 9.10; AR, 5%); drinking unpasteurized goat's milk (aOR, 5.09; 95% CLs, 1.45, 17.80; AR, 4%); and having 3 or more kittens (aOR, 27.89; 95% CLs, 5.72, 135.86; AR, 10%). Eating raw oysters, clams, or mussels (aOR, 2.22; 95% CLs, 1.07, 4.61; AR, 16%) was significant in a separate model among persons asked this question. Subgroup results are also provided for women and for pregnant women. CONCLUSIONS: In the United States, exposure to certain raw or undercooked foods and exposure to kittens are risk factors for T. gondii infection. Knowledge of these risk factors will help to target prevention efforts.

National outbreak of Acanthamoeba keratitis associated with use of a contact lens solution, United States.

An outbreak of Acanthamoeba keratitis, a rare, potentially blinding, corneal infection, was detected in the United States in 2007; cases had been increasing since 2004. A case-control study was conducted to investigate the outbreak. We interviewed 105 case-patients from 30 states and 184 controls matched geographically and by contact lens use. Available contact lenses, cases, solutions, and corneal specimens from case-patients were cultured and tested by molecular methods. In multivariate analyses, case-patients had significantly greater odds of having used Advanced Medical Optics Complete Moisture Plus (AMOCMP) solution (odds ratio 16.9, 95% confidence interval 4.8-59.5). AMOCMP manufacturing lot information was available for 22 case-patients, but none of the lots were identical. Three unopened bottles of AMOCMP tested negative for Acanthamoeba spp. Our findings suggest that the solution was not intrinsically contaminated and that its anti-Acanthamoeba efficacy was likely insufficient. Premarket standardized testing of contact lens solutions for activity against Acanthamoeba spp. is warranted.

Resistance of Acanthamoeba cysts to disinfection in multiple contact lens solutions.

Acanthamoebae are free-living amoebae found in the environment, including soil, freshwater, brackish water, seawater, hot tubs, and Jacuzzis. Acanthamoeba species can cause keratitis, a painful vision-threatening infection of the cornea, and fatal granulomatous encephalitis in humans. More than 20 species of Acanthamoeba belonging to morphological groups I, II, and III distributed in 15 genotypes have been described. Among these, Acanthamoeba castellanii, A. polyphaga, and A. hatchetti are frequently identified as causing Acanthamoeba keratitis (AK). Improper contact lens care and contact with nonsterile water while wearing contact lenses are known risk factors for AK. During a recent multistate outbreak, AK was found to be associated with the use of Advanced Medical Optics Complete MoisturePlus multipurpose contact lens solution, which was hypothesized to have had insufficient anti-Acanthamoeba activity. As part of the investigation of that outbreak, we compared the efficacies of 11 different contact lens solutions against cysts of A. castellanii, A. polyphaga, and A. hatchetti (the isolates of all species were genotype T4), which were isolated in 2007 from specimens obtained during the outbreak investigation. The data, generated with A. castellanii, A. polyphaga, and A. hatchetti cysts, suggest that the two contact lens solutions containing hydrogen peroxide were the only solutions that showed any disinfection ability, with 0% and 66% growth, respectively, being detected with A. castellanii and 0% and 33% growth, respectively, being detected with A. polyphaga. There was no statistically significant difference in disinfection efficacy between the 11 solutions for A. hatchetti.

A simple method for collecting measured whole blood with quantitative recovery of antibody activities for serological surveys.

Compliance and acceptance for the finger-prick method of blood collection is generally better than for venipuncture. A finger-prick method of blood collection with quantitative antibody recovery is even more important for seroepidemiological surveys. Finger-prick blood collected and dried onto filter paper has been used; but, unfortunately, this method has several disadvantages, including loss of antibody activity, possible contact contamination from blood spots on adjacent filter papers, and difficulties in extracting antibodies, justifying the search for other methods of collecting and transporting blood samples. We report on a simple method of collecting a measured amount of finger-prick blood onto a sample pad, which is immediately transferred to storage/extraction buffer. The diluted blood sample is never dried, and because of the storage buffer, can be transported and stored without refrigeration. Furthermore, the diluted blood samples can then be tested directly without further preparation. We systematically compared several storage/extraction buffers and commercially available filter papers. We showed that antibody recovery was not significantly affected by the type of filter papers used but was significantly affected by the storage/extraction buffer used. The best such buffer is StabilZyme Select.

Combined sewage overflows (CSO) are major urban breeding sites for Culex quinquefasciatus in Atlanta, Georgia.

A longitudinal study of mosquito ecology in Tanyard Creek, an urban stream in Atlanta, GA, that receives combined storm and waste water effluent from the Atlanta combined sewage overflow system, was undertaken in 2006. Culex quinquefasciatus was the dominant species found, but Culex restuans was also abundant during the spring with limited numbers of Culex nigripalpis and Anopheles punctipennis also collected. Significant differences in mosquito densities were found with greater densities associated with side pools of water and stagnant water. Mosquito numbers are regulated largely by flooding of the stream by effluent discharges exceeding 15 kgal/min. These floods are associated with significant immediate reductions, but not complete elimination, of mosquitoes from Tanyard Creek. Mosquito numbers rebound within 5-10 days after such floods and rapidly reach high densities.

Assessment of transmission-blocking activity of candidate Pvs25 vaccine using gametocytes from chimpanzees.

Macaca mulatta monkeys were immunized with the candidate transmission-blocking vaccine against Plasmodium vivax, Pvs25, combined with alum or Montanide ISA 720. Efficacy was measured by combining post-immunization sera with gametocytes obtained from infections induced in chimpanzees using membrane-feeding techniques. The results indicate that immunization of M. mulatta monkeys with Pvs25 and Montanide ISA 720 was more effective than with alum in efficacy and resulted in the maintenance of a lasting transmission-blocking immunity to P. vivax. This was evident two weeks after the second immunization, and more strongly demonstrable 62 and 152 days after the second immunization. This transmission-blocking activity was strongly reinforced by a third immunization given 181 days after the primary immunization, as measured three weeks later by indirect membrane feeding. The use of gametocytes of P. vivax derived from infections induced in chimpanzees can contribute to the selection of appropriate constructs, formulations, and immunization regimens for the development of effective transmission-blocking vaccines.

Preliminary observations on the efficacy of a recombinant multistage Plasmodium falciparum vaccine in Aotus nancymai monkeys.

A vaccine trial was conducted to determine the efficacy of a multicomponent candidate vaccine, FALVAC-1, against Plasmodium falciparum in Aotus nancymai monkeys. After two immunizations, animals were challenged intravenously with parasites of the Vietnam Oak Knoll (FVO) strain of P. falciparum. The primary outcome was to determine the protective response of the monkeys to immunization with the FALVAC-1 antigen produced in baculovirus when combined with different adjuvants (alum, QS-21, ASO2a, CRL1005/oil, and CRL1005/saline) as compared with FALVAC-1 with FCA/FIA and antigen alone. When compared with the monkeys immunized with FALVAC-1 alone, FALVAC-1 with FCA/FIA reduced the mean parasite count (to Day 11), reduced the mean accumulated parasitemia (through Day 11), and extended the number of days to treatment. None of the other 5 antigen-adjuvant combinations were able to provide discernable levels of protection based on log(parasitemia) and log(cumulative parasitemia) to Day 11.

Enzyme immunoassay of Cryptosporidium-specific immunoglobulin G antibodies to assess longitudinal infection trends in six communities in British Columbia, Canada.

A newly developed enzyme-linked immunosorbent assay (ELISA) that detects immunoglobulin G antibodies to the 27-kDa Cryptosporidium parvum sporozoite surface antigen was used to test 4,097 sera collected from pregnant women in 6 communities in British Columbia, Canada, between January 1996, and December 1997. Waterborne outbreaks of cryptosporidiosis occurred in two of the study communities during the period of follow-up, and ELISA seropositivity was high in all six communities during the study period (77% positive to 92% positive). In the community with the largest outbreak, levels of antibody to the 27-kDa antigen increased rapidly and then decayed to background levels within 3-4 months of the peak of the epidemic curve. Trends in serologic reactivity were complex in all communities, and increased antibody levels not related temporally to known waterborne outbreaks were also observed. Serological assays may provide more accurate information regarding community levels of Cryptosporidium infection.

Malaria chemoprophylaxis and the serologic response to measles and diphtheria-tetanus-whole-cell pertussis vaccines.

BACKGROUND: Acute malaria has been associated with a decreased antibody response to tetanus and diphtheria toxoids, meningococcal, salmonella, and Hib vaccines. Interest in giving malaria drug therapy and prevention at the time of childhood immunizations has increased greatly following recent trials of intermittent preventive therapy during infancy (IPTi), stimulating this re-analysis of unpublished data. The effect of malaria chemoprophylaxis on vaccine response was studied following administration of measles vaccines and diphtheria-tetanus-whole cell pertussis (DTP) vaccines. METHODS: In 1975, six villages divided into two groups of children < or = 74 months of age from Burkina Faso, were assigned to receive amodiaquine hydrochloride chemoprophylaxis (CH+) every two weeks for seven months or no chemoprophylaxis (CH-). After five months, children in each group received either one dose of measles or two doses of DTP vaccines. RESULTS: For recipients of the measles vaccine, the seroconversion rates in CH+ and CH- children, respectively, were 93% and 96% (P > 0.05). The seroresponse rates in CH+ and CH- children respectively, were 73% and 86% for diphtheria (P > 0.05) and 77% and 91% for tetanus toxoid (P > 0.05). In a subset analysis, in which only children who strictly adhered to chemoprophylaxis criteria were included, there were, likewise, no significant differences in seroconversion or seroresponse for measles, diphtheria, or tetanus vaccines (P > 0.05). While analysis for pertussis showed a 43% (CH+) and 67% (CH-) response (P < 0.05), analyses using logistic regression to control for sex, age, chemoprophylaxis, weight-for-height Z-score, and pre-vaccination geometric mean titer (GMT), demonstrated that chemoprophylaxis was not associated with a significantly different conversion rate following DTP and measles vaccines. Seven months of chemoprophylaxis decreased significantly the malaria IFA and ELISA GMTs in the CH+ group. CONCLUSION: Malaria chemoprophylaxis prior to vaccination in malaria endemic settings did not improve or impair immunogenicity of DTP and measles vaccines. This is the first human study to look at the association between malaria chemoprophylaxis and the serologic response to whole-cell pertussis vaccine.

Malaria surveillance--United States, 1999.

PROBLEM/CONDITION: Malaria is caused by four species of intraerythrocytic protozoa of the genus Plasmodium (i.e., P. falciparum, P. vivax, P. ovale, or P. malariae). Malaria is transmitted by the bite of an infective female Anopheles sp. mosquito. The majority of malaria infections in the United States occur in persons who have traveled to areas with ongoing transmission. In the United States, cases can occur through exposure to infected blood products, by congenital transmission, or locally through mosquitoborne transmission. Malaria surveillance is conducted to identify episodes of local transmission and to guide prevention recommendations for travelers. PERIOD COVERED: Cases with onset of illness during 1999. DESCRIPTION OF SYSTEM: Malaria cases confirmed by blood films are reported to local and state health departments by health-care providers or laboratory staff. Case investigations are conducted by local and state health departments, and reports are transmitted to CDC through the National Malaria Surveillance System (NMSS). Data from NMSS serve as the basis for this report. RESULTS: CDC received reports of 1,540 cases of malaria with an onset of symptoms during 1999 among persons in the United States or one of its territories. This number represents an increase of 25.5% from the 1,227 cases reported for 1998. P. falciparum, P. vivax, P. malariae, and P. ovale were identified in 46.0%, 30.7%, 4.6%, and 3.6% of cases, respectively. More than one species was present in 12 patients (0.8% of total). The infecting species was unreported or undetermined in 223 (14.5%) cases. The number of reported malaria cases acquired in Africa increased 27.6% (n = 901), compared with 1998, and an increase of 2.9% (n = 246) occurred in cases acquired in Asia, compared with 1998. Cases from the Americas increased by 19.7% (n = 274) from 1998. Of 831 U.S. civilians who acquired malaria abroad, 159 (19.1%) reported that they had followed a chemoprophylactic drug regimen recommended by CDC for the area to which they had traveled. Three patients became infected in the United States, all through probable local mosquitoborne transmission. Five deaths were attributed to malaria, all caused by P. falciparum. INTERPRETATION: The 25.5% increase in malaria cases in 1999, compared with 1998, resulted primarily from increases in cases acquired in Africa and the Americas. This increase is possibly related to a change in the system by which states report to CDC, but it could also have resulted from local changes in disease transmission, increased travel to these regions, improved reporting to state and local health departments, or a decreased use of effective antimalarial chemoprophylaxis. In the majority of reported cases, U.S. civilians who acquired infection abroad were not on an appropriate chemoprophylaxis regimen for the country where they acquired malaria. PUBLIC HEALTH ACTIONS: Additional information was obtained concerning the five fatal cases and the three infections acquired in the United States. The NMSS surveillance form was modified to gather more detailed information regarding compliance with prescribed chemoprophylaxis regimens. Persons traveling to a malarious area should take one of the recommended chemoprophylaxis regimens appropriate to the region of travel, and travelers should use personal protection measures to prevent mosquito bites. Any person who has been to a malarious area and who subsequently develops a fever or influenza-like symptoms should seek medical care immediately; investigation should include a blood-film test for malaria. Malaria infections can be fatal if not diagnosed and treated promptly. Recommendations concerning prevention of malaria can be obtained from CDC.

Malaria surveillance--United States, 2001.

PROBLEM/CONDITION: Malaria is caused by any of four species of intraerythrocytic protozoa of the genus Plasmodium (i.e., P. falciparum, P. vivax, P. ovale, or P. malariae). These parasites are transmitted by the bite of an infective female Anopheles sp. mosquito. The majority of malaria infections in the United States occur among persons who have traveled to areas with ongoing transmission. In the United States, cases can occur through exposure to infected blood products, by congenital transmission, or by local mosquitoborne transmission. Malaria surveillance is conducted to identify episodes of local transmission and to guide prevention recommendations for travelers. PERIOD COVERED: This report covers cases with onset of illness in 2001. DESCRIPTION OF SYSTEM: Malaria cases confirmed by blood film are reported to local and state health departments by health-care providers or laboratory staff. Case investigations are conducted by local and state health departments, and reports are transmitted to CDC through the National Malaria Surveillance System (NMSS). Data from NMSS serve as the basis for this report. RESULTS: CDC received reports of 1,383 cases of malaria with an onset of symptoms in 2001 among persons in the United States or one of its territories. This number represents a decrease of 1.4% from the 1,402 cases reported for 2000. P. falciparum, P. vivax, P. malariae, and P. ovale were identified in 50.1%, 27.8%, 4.5%, and 3.6% of cases, respectively. Fourteen patients (1.0% of total) were infected by >/=2 species. The infecting species was unreported or undetermined in 179 (12.9%) cases. Compared with 2000, the number of reported malaria cases acquired in Africa increased by 13.2% (n = 886), whereas the number of cases acquired in Asia (n = 163) and the Americas (n = 240) decreased by 31.5% and 11.4%, respectively. Of 891 U.S. civilians who acquired malaria abroad, 180 (20.2%) reported that they had followed a chemoprophylactic drug regimen recommended by CDC for the area to which they had traveled. Two patients became infected in the United States, one through congenital transmission and one whose infection cannot be linked epidemiologically to secondary cases. Eleven deaths were attributed to malaria, 10 caused by P. falciparum and one caused by P. ovale. INTERPRETATION: The 1.4% decrease in malaria cases in 2001, compared with 2000, resulted primarily from a decrease in cases acquired in Asia and the Americas, but this decrease was offset by an increase in the number of cases acquired in Africa. This decrease probably represents year-to-year variation in malaria cases, but also could have resulted from local changes in disease transmission, decreased travel to malaria-endemic regions, fluctuation in reporting to state and local health departments, or an increased use of effective antimalarial chemoprophylaxis. In the majority of reported cases, U.S. civilians who acquired infection abroad were not on an appropriate chemoprophylaxis regimen for the country in which they acquired malaria. PUBLIC HEALTH ACTIONS: Additional information was obtained concerning the 11 fatal cases and the two infections acquired in the United States. Persons traveling to a malarious area should take one of the recommended chemoprophylaxis regimens appropriate for the region of travel, and travelers should use personal protection measures to prevent mosquito bites. Any person who has been to a malarious area and who subsequently develops a fever or influenza-like symptoms should seek medical care immediately and report their travel history to the clinician; investigation should include a blood-film test for malaria. Malaria infections can be fatal if not diagnosed and treated promptly. Recommendations concerning malaria prevention can be obtained from CDC by calling the Malaria Hotline at 770-488-7788 or by accessing CDC's Internet site at http://www.cdc.gov/travel.

A retrospective examination of the effect of fever and microgametocyte count on mosquito infection on humans infected with Plasmodium vivax.

A retrospective examination was made of archival data collected between 1940 and 1963 on the infection of mosquitoes with the St. Elizabeth strain of Plasmodium vivax. Patients were undergoing malariatherapy for the treatment of neurosyphilis. A total of 845 lots of Anopheles quadrimaculatus mosquitoes were fed during primary infections and 76 during secondary infections. Average percentage infection during the primary infection was 56.55% versus 49.83% during the secondary infection. There appeared to be no relationship between microgametocye density, asexual parasite count, and percentage infection. However, very high fevers appear to have a significant effect on infection rates. Persons with fever > or = 105 degrees F showed the lowest rates of infectivity regardless of parasitemia; persons with moderate (101-104.8 degrees F) fever produced somewhat higher rates, and persons with no fever had the highest levels of infection at all parasitemia levels greater than 1,500/microL

A retrospective examination of reinfection of humans with Plasmodium vivax.

A retrospective examination was made of archival data collected between 1940 and 1963 to determine the impact of reinfection of patients with Plasmodium vivax with homologous and heterologous strains of the parasite. Following reinfection of 14 patients with a homologous strain, the geometric mean maximum parasite count was reduced from 9,101/microL during the primary infection to 998/microL and the geometric mean daily parasite count for the first 20 days was reduced from 923/microL to 16/microL. Following reinfection of 22 patients with heterologous strains of P. vivax, the geometric mean maximum parasite count was 8,460/microL during the primary infection versus a secondary level of 9,196/microL and the geometric mean daily parasite count decreased from 847/microL/day to 335/microL/day. Reductions in fever episodes > or =101 degrees F and > or = 104 degrees F appeared to be a more sensitive measure of clinical immunity. Fever episodes > or =104 degrees F in patients with homologous strain reinfections decreased from 1.92 episodes per week to 0.18 compared with 1.24 to 0.57 in patients with heterologous infections. Fever episodes > or =101 degrees F decreased from 2.98 to 0.60 in the homologous strain compared with 2.08 to 1.07 for the heterologous infections. The average maximum fever temperature in the homologous group was 106 degrees F during the primary infection versus 103.4 degrees F for the secondary infection compared with 105.8 degrees F during the primary infections versus 105.6 degrees F for the secondary infection in the heterologous patients.

A retrospective examination of anemia during infection of humans with Plasmodium vivax.

A retrospective examination was made of archival data on 98 patient episodes of infection with Plasmodium vivax occurring over a period of 4-11 weeks to document changes in hemoglobin (Hb) concentrations associated with continuing parasitemia. The mean percentage change in the Hb concentration for each of the 10 seven-day intervals was -13.4, -10.9, -4.8, 0.12, 0.94, 4.0, 0.69, 11.6, 2.4, and 8.3, respectively. An equilibrium appeared to be established between weeks 4 and 6. Decreases in Hb concentrations were greatest following the first week of parasitemia. Total restoration to preinfection levels did not occur during persistent parasitemia.