Malaria Notifications Research Articles

The impact of hydropower dam construction on malaria incidence: Space-time analysis in the Brazilian Amazon.

During the first two decades of the 21st century, Brazil carried out massive public investments on infrastructure projects, such as large hydropower dams, with potential impact on population health. Here we characterize local malaria transmission and its potential spread during the construction of three large hydropower dams in the Brazilian Amazon. We focus on Porto Velho (PVH), in Rondônia state, where the Santo Antônio and Jirau dams were built (2008-2013), and Altamira region (ATM), in Pará state, where the construction of the Belo Monte dam took place (2011-2016). Analyzed data cover 4 years before, 6 years during, and 4 years after each dam construction. In total, we utilized malaria case notifications entered into the electronic malaria notification system of the Ministry of Health of Brazil between January 2004 and December 2020 (n = 39,977,167 malaria notifications). First, we used Interrupted Time-Series Analysis (ITSA) to assess temporal changes in malaria notifications in the study sites. Then, we conducted a space-time cluster analysis to investigate the potential of malaria spread from the study sites (sources) to elsewhere (sinks). Finally, we present the sociodemographic characteristics of exported cases over time using multivariate logistic regressions. Our results show that there was no upsurge in malaria cases in the study sites and exported cases did not trigger outbreaks in other localities. Exported malaria infections originating from PVH and ATM were typically found in working age literate males involved in mining, farming or traveling. We suggest that efficient control measures, such as ensuring timely diagnosis and treatment; fostering integrated vector control; promoting health education; and prevention, detection and containment of outbreaks, if properly implemented and sustained, may prevent local and introduced malaria outbreaks during and after hydropower dam construction in the Amazon.

Notification of malaria cases in the Brazilian Amazon Basin from 2010 to 2020: an analysis of the reporting times

BackgroundAs controlling malaria transmission remains a public-health challenge in the Brazilian Amazon basin, the National Surveillance System for Malaria (SIVEP-MALARIA) has registered malaria notifications for over fifteen years helping in the decision-making on control and elimination. As a surveillance database, the system is prone to reporting delays, and knowledge about reporting patterns is essential in decisions.MethodsThis study contains an analysis of temporal and state trends of reporting times in a total of 1,580,617 individual malaria reports from January 2010 to December 2020, applying procedures for statistical distribution fitting. A nowcasting technique was applied to show an estimation of number of cases using a statistical model of reporting delays.ResultsReporting delays increased over time for the states of Amazonas, Rondônia, Roraima, and Pará. Amapá has maintained a similar reporting delay pattern, while Acre decreased reporting delay between 2010 and 2020. Predictions were more accurate in states with lower reporting delays. The temporal evolution of reporting delays only showed a decrease in malaria reports in Acre from 2010 to 2020.ConclusionMalaria notifications may take days or weeks to enter the national surveillance database. The reporting times are likely to impact incidence estimation over periods when data is incomplete, whilst the impact of delays becomes smaller for retrospective analysis. Short-term assessments for the estimation of malaria incidence from the malaria control programme must deal with reporting delays.

Risk factor of plasmodium knowlesi infection in Sabah Borneo Malaysia, 2020: A population-based case-control study.

BackgroundIn the Malaysian state of Sabah, P. knowlesi notifications increased from 2% (59/2,741) of total malaria notifications in 2004 to 98% (2030/2,078) in 2017. There was a gap regarding P. knowlesi acquisition risk factors related to practice specifically in working age group. The main objective of this study was to identify the risk factors for acquiring P. knowlesi infection in Sabah among the working age group.Methods and methodsThis retrospective population-based case-control study was conducted in Ranau district to assess sociodemographic, behavioural and medical history risk factors using a pretested questionnaire. The data were entered and analyzed using IBM SPSS version 23. Bivariate analysis was conducted using binary logistic regression whereas multivariate analysis was conducted using multivariable logistic regression. We set a statistical significance at p-value less than or equal to 0.05.ResultsA total of 266 cases and 532 controls were included in the study. Male gender (AOR = 2.71; 95% CI: 1.63–4.50), spending overnight in forest (AOR = 1.92; 95% CI: 1.20–3.06), not using mosquito repellent (AOR = 2.49; 95% CI: 1.36–4.56) and history of previous malaria infection (AOR = 49.34; 95% CI: 39.09–78.32) were found to be independent predictors of P. knowlesi infection.ConclusionsThis study showed the need to strengthen the strategies in preventing and controlling P. knowlesi infection specifically in changing the practice of spending overnight in forest and increasing the usage of personal mosquito repellent.

20 years of Malaria notifications in Bologna AUSL

Abstract Background Notification of confirmed or suspected cases of Malaria is compulsory in Italy. It is essential to optimize control measures in case of imported and indigenous events, considering that the main local vector, Anopheles labranchiae, is still present in Italy. Methods Descriptive analysis of malaria cases notified from Bologna local health authority (AUSL) from January 2000 to December 2019. Results In the period 2000-2019, out of the 248 Malaria cases notified to the AUSL, 161 were males, and 87 were females, with median age of 33 (IQR: 42-25). All the cases were sporadic and travel-related. The main reasons for travelling were: return to the country of origin (n = 139, 56,0%), tourism (n = 39, 15,7%), work (n = 30, 12,1%), and immigration (n = 13, 5,2%). 86 (34,7%) cases were born in Italy, 43 (17,3%) in Nigeria, 27 (10,9%) in Cameroon, and 17 (6,9%) in Ghana. The cases were imported from Nigeria (n = 56, 22,9%), Cameroon (n = 30, 12,2%), Ghana (n = 26, 10,6%), Ivory Coast (n = 24, 9,8%). Most of the cases were not taking any drug for Malaria chemoprophylaxis (n = 214, 86,6%), 20 cases (8,1%) properly completed the prophylaxis, while 13 cases (5,3%) started chemoprophylaxis but they didn't complete it. The etiological agent identified was Plasmodium falciparum in 176 cases (71,0%), P. vivax in 26 cases (10,5%). Among the former cases 49 (32,2%) were contracted in Nigeria, 29 (19,1%) in Cameroon, 23 (15,1%) in Ghana, 20 (13,2%) in Ivory Coast, 10 (6,6%) in Senegal. 11 (68,8%) cases of P. vivax were contracted in Pakistan. Conclusions Epidemiological data collected from Bologna AUSL are consistent with those described from Istituto Superiore di Sanità: the majority of cases was comprised of foreigners, the great majority of cases was imported from Africa. P. Falciparum was prevalent in Africa while P. vivax was prevalent in Asia. Key messages The knowledge of the epidemiological situation allows public health workers to advise international travelers focusing on those most at risk of contracting Malaria. Periodic assessment of local epidemiology is necessary to evaluate if data are consistent with those described from international literature.

Análise dos Aspectos Epidemiológicos da Malária na região Nordeste do Brasil

Epidemiological studies on the occurrence of malaria are of paramount importance for detecting outbreaks and epidemics, aiming to contribute to greater knowledge and timely control of the disease in different regions of Brazil, since each region has its specific Anopheles fauna. This study aimed to analyze epidemiological aspects of malaria in northeastern Brazil. Cross-sectional, retrospective study with a quantitative and descriptive approach by consulting the database of the Ministry of Health Notification Information System from January 2015 to February 2020. 490 malaria notifications were verified, 377 of which were cases female. A greater number of cases was identified between 20 and 29 years old, totaling 250 diagnosed cases. Regarding color, there were 323 cases of mixed race. The results of this study made it possible to describe the epidemiological profile of malaria in the states of northeastern Brazil, showing that despite the efforts of the Ministry of Health, there are still cases reported without full control of the disease transmission chain.

Evaluating a 24-h mobile reporting system for malaria notifications in comparison with a paper-based system in South Africa, 2015

BackgroundAs South Africa strives to achieve malaria elimination by 2018 (zero local cases) the country needs to strengthen its disease surveillance system by reducing the timeliness from case diagnosis to notification of key stakeholders in the malaria programme. This study evaluated the feasibility of a 24-h mobile reporting system, designed for speeding up malaria notifications, from primary healthcare facilities to district, provincial, and national malaria programmes in South Africa.MethodsA prospective descriptive study utilizing primary data collected from structured interviews with healthcare workers in public healthcare facilities was used to compare two reporting systems (24-h mobile reporting system and the paper-based reporting system) in malaria endemic provinces (Limpopo, Mpumalanga and KwaZulu-Natal). Data on completeness of reporting, simplicity, user acceptability and technical limitations were analysed. A Wilcoxon signed-rank test was used to compare the time difference between the two reporting systems.ResultsThere were 1819 cases of malaria reported through the paper-based system, and 63.2% (1149) of those cases were also reported through the 24-h mobile reporting system. Out of the 272 healthcare workers who were interviewed, 40% (108) had seen malaria patients and reported a case through the 24-h mobile reporting system. The median time for cases to be reported through the 24-h mobile reporting system was significantly shorter at < 1 day (range < 1 to 31 days) compared to the paper-based system at 3 days (range 2 to > 39 days) (p < 0.001). It was found that 26% (28) were able to use the system and send reports within 2 min, 94% (256) were willing to continue to use the system. Of the 108 healthcare workers who reported a case, 18.5% (20) experienced network challenges.ConclusionsThe 24-h mobile reporting system is user friendly and trained healthcare workers are willing to use the system, despite network limitations. The 24-h mobile reporting system reduces the time required for diagnosed cases to be notified by the health care facility to district, provincial and national levels. The 24-h mobile reporting system is a feasible option for malaria notification in South Africa and will assist with early detection of malaria outbreaks.

Changes in malaria epidemiology in Germany, 2001\u20132016: a time series analysis

BackgroundGerman surveillance data showed a sharp rise of malaria cases in 2014 and 2015 due to the increased arrival of refugees from malaria endemic countries. A time series analysis of data from 2001 to 2016 was performed in order to describe the epidemiology of imported malaria in Germany in general and of the recent increase in particular.ResultsIn total, 11,678 malaria cases were notified between 2001 and 2016 (range 526–1063 cases/year). Newly arriving refugees averaged 10 cases/year (1.5%) in 2001–13 and 292.5 cases/year (28.3%) in 2014–15. Plasmodium (P.) falciparum was the most frequently reported species (range 57.2–85.8%), followed by P. vivax (range during 2001–2013: 7.6–18.1%; during 2014–2015, mean 31.3%). In 2014–15, 22.3% of all P. vivax cases were refugees from Eritrea and 3.3% from other countries of the Horn of Africa; in 2015 and 2016, 19.5% were refugees from Afghanistan and Pakistan. Five P. knowlesi malaria infections were reportedly acquired in Thailand between 2012 and 2016. Total numbers of malaria notifications among native Germans and residents with migration background showed an increasing trend since 2007. Chemoprophylaxis use was reported for 24.3% (1695/6984) of cases and showed a declining trend. Native German cases took significantly more frequently chemoprophylaxis than cases with migration background (32.6% vs. 17.9%; p < 0.001).Discussion/conclusionsThe steep rise in vivax malaria notifications in 2014 and 2015 was mainly due to newly arriving refugees from Eritrea but also from other countries of the Horn of Africa and South Asia. Clinicians should include malaria in their differential diagnosis in case of a febrile illness in the respective population and consider vivax malaria even if arrival to Germany dates back several months. Over the past 10 years, malaria notifications among native Germans and residents with migration background showed an increasing trend. Use of chemoprophylaxis was insufficient in both groups and deteriorating. New strategies need to be found to increase compliance to chemoprophylaxis recommendations. The surveillance provides valuable data for epidemiological assessment of imported malaria in Germany.

Increase in imported malaria in the Netherlands in asylum seekers and VFR travellers

BackgroundMalaria is a notifiable disease in the Netherlands, a non-endemic country. Imported malaria infections occur regularly among travellers, migrants and visitors. Surveillance data were analysed from 2008 to 2015. Trends in amounts of notifications among risk groups were analysed using Poisson regression. For asylum seekers, yearly incidence was calculated per region of origin, using national asylum request statistics as denominator data. For tourists, denominator data were used from travel statistics to estimate incidence per travel region up to 2012.ResultsA modest increase in overall imported malaria notifications occurred in 2008–2015 (from 222 in 2008 to 344 in 2015). Notably, in 2014 and 2015 sharp increases were seen in malaria among travellers visiting friends and relatives (VFR), and in asylum seekers. Of all Plasmodium falciparum infections, most (1254/1337; 93.8%) were imported from Africa; 1037/1337 (77.6%) were imported from Central and West Africa. Malaria in VFR was mostly caused by P. falciparum infection after visiting Ghana (22%) or Nigeria (19%). Malaria in asylum seekers was mostly caused by Plasmodium vivax infection from the Horn of Africa. The large number of notifications in asylum seekers resulted from both an increase in number of asylum seekers and a striking increase of malaria incidence in this group. Incidence of malaria in asylum seekers from the Horn of Africa ranged between 0.02 and 0.3% in 2008–2013, but rose to 1.6% in 2014 and 1.3% in 2015. In 2008–2012, incidence in tourists visiting Central and West Africa dropped markedly.ConclusionsImported malaria is on the rise again in the Netherlands, most notably since 2013. This is mostly due to immigration of asylum seekers from the Horn of Africa. The predominance of P. vivax infection among asylum seekers warrants vigilance in health workers when a migrant presents with fever, as relapses of this type of malaria can occur long after arrival in the Netherlands.

Changing epidemiology of malaria in Sabah, Malaysia: increasing incidence of Plasmodium knowlesi.

BackgroundWhile Malaysia has had great success in controlling Plasmodium falciparum and Plasmodium vivax, notifications of Plasmodium malariae and the microscopically near-identical Plasmodium knowlesi increased substantially over the past decade. However, whether this represents microscopic misdiagnosis or increased recognition of P. knowlesi has remained uncertain.MethodsTo describe the changing epidemiology of malaria in Sabah, in particular the increasing incidence of P. knowlesi, a retrospective descriptive study was undertaken involving a review of Department of Health malaria notification data from 2012–2013, extending a previous review of these data from 1992–2011. In addition, malaria PCR and microscopy data from the State Public Health Laboratory were reviewed to estimate the accuracy of the microscopy-based notification data.ResultsNotifications of P. malariae/P. knowlesi increased from 703 in 2011 to 815 in 2012 and 996 in 2013. Notifications of P. vivax and P. falciparum decreased from 605 and 628, respectively, in 2011, to 297 and 263 in 2013. In 2013, P. malariae/P. knowlesi accounted for 62% of all malaria notifications compared to 35% in 2011. Among 1,082 P. malariae/P. knowlesi blood slides referred for PCR testing during 2011–2013, there were 924 (85%) P. knowlesi mono-infections, 30 (2.8%) P. falciparum, 43 (4.0%) P. vivax, seven (0.6%) P. malariae, six (0.6%) mixed infections, 31 (2.9%) positive only for Plasmodium genus, and 41 (3.8%) Plasmodium-negative. Plasmodium knowlesi mono-infection accounted for 32/156 (21%) and 33/87 (38%) blood slides diagnosed by microscopy as P. falciparum and P. vivax, respectively. Twenty-six malaria deaths were reported during 2010–2013, including 12 with ‘P. malariae/P. knowlesi’ (all adults), 12 with P. falciparum (seven adults), and two adults with P. vivax.ConclusionsNotifications of P. malariae/P. knowlesi in Sabah are increasing, with this trend likely reflecting a true increase in incidence of P. knowlesi and presenting a major threat to malaria control and elimination in Malaysia. With the decline of P. falciparum and P. vivax, control programmes need to incorporate measures to protect against P. knowlesi, with further research required to determine effective interventions.Electronic supplementary materialThe online version of this article (doi:10.1186/1475-2875-13-390) contains supplementary material, which is available to authorized users.

Malaria in the state of Rio de Janeiro, Brazil, an Atlantic Forest area: an assessment using the health surveillance service.

The lethality of malaria in the extra-Amazonian region is more than 70 times higher than in Amazonia itself. Recently, several studies have shown that autochthonous malaria is not a rare event in the Brazilian southeastern states in the Atlantic Forest biome. Information about autochthonous malaria in the state of Rio de Janeiro (RJ) is scarce. This study aims to assess malaria cases reported to the Health Surveillance System of the State of Rio de Janeiro between 2000-2010. An average of 90 cases per year had parasitological malaria confirmation by thick smear. The number of malaria notifications due to Plasmodium falciparum increased over time. Imported cases reported during the period studied were spread among 51% of the municipalities (counties) of the state. Only 35 cases (4.3%) were autochthonous, which represents an average of 3.8 new cases per year. Eleven municipalities reported autochthonous cases; within these, six could be characterised as areas of residual or new foci of malaria from the Atlantic Forest system. The other 28 municipalities could become receptive for transmission reintroduction. Cases occurred during all periods of the year, but 62.9% of cases were in the first semester of each year. Assessing vulnerability and receptivity conditions and vector ecology is imperative to establish the real risk of malaria reintroduction in RJ.

Increasing Incidence of Plasmodium knowlesi Malaria following Control of P. falciparum and P. vivax Malaria in Sabah, Malaysia

BackgroundThe simian parasite Plasmodium knowlesi is a common cause of human malaria in Malaysian Borneo and threatens the prospect of malaria elimination. However, little is known about the emergence of P. knowlesi, particularly in Sabah. We reviewed Sabah Department of Health records to investigate the trend of each malaria species over time.MethodsReporting of microscopy-diagnosed malaria cases in Sabah is mandatory. We reviewed all available Department of Health malaria notification records from 1992–2011. Notifications of P. malariae and P. knowlesi were considered as a single group due to microscopic near-identity.ResultsFrom 1992–2011 total malaria notifications decreased dramatically, with P. falciparum peaking at 33,153 in 1994 and decreasing 55-fold to 605 in 2011, and P. vivax peaking at 15,857 in 1995 and decreasing 25-fold to 628 in 2011. Notifications of P. malariae/P. knowlesi also demonstrated a peak in the mid-1990s (614 in 1994) before decreasing to ≈100/year in the late 1990s/early 2000s. However, P. malariae/P. knowlesi notifications increased >10-fold between 2004 (n = 59) and 2011 (n = 703). In 1992 P. falciparum, P. vivax and P. malariae/P. knowlesi monoinfections accounted for 70%, 24% and 1% respectively of malaria notifications, compared to 30%, 31% and 35% in 2011. The increase in P. malariae/P. knowlesi notifications occurred state-wide, appearing to have begun in the southwest and progressed north-easterly.ConclusionsA significant recent increase has occurred in P. knowlesi notifications following reduced transmission of the human Plasmodium species, and this trend threatens malaria elimination. Determination of transmission dynamics and risk factors for knowlesi malaria is required to guide measures to control this rising incidence.

Malaria notifications in the Australian Defence Force from 1998 to 2007

We report here a retrospective analysis of all malaria cases in military personnel reported to the Australian Defence Force (ADF) Central Malaria Register from 1998 to 2007. A total of 637 cases of malaria were notified affecting 487 individuals. Of these 85.9% (547) were infected with Plasmodium vivax malaria and 10.2% (65) with P. falciparum malaria. The majority of cases were from Timor Leste (78.5%, 501/637). Malaria attack rates of 0.9% (369/40 571), 1.1% (52/4776) and 0.4% (20/5345) were seen in Timor Leste, Bougainville and the Solomon Islands, respectively. The median period following departure from a malarious country to presentation of P. falciparum was 17 d (range 1-47 d) and for a primary presentation of P. vivax malaria was 86 d (range 1-505 d). Increasing the dose of primaquine from 22.5mg daily to 30mg daily for 14 d for radical cure of P. vivax malaria reduced the failure rate from 46.6% (35/75) to 9.4% (17/181) in subjects returning from Timor Leste. Malaria remains a serious problem for ADF soldiers deploying to malarious areas, particularly the incidence of relapsing vivax malaria and the tolerance of these vivax strains to primaquine.

Cerebral malaria admissions in Papua New Guinea may show inter-annual cyclicity: An example of about a 1.5-year cycle for malaria incidence in Burundi

AbstractBest available descriptions of malaria incidence and mortality dynamics are important to better plan and evaluate the implementation of programs to monitor (e.g., remote sensing) and control the disease, especially in endemic zones. This was stressed recently by Cibulskis et al (2007) in the view of completeness of monthly reporting for cerebral malaria admissions in Papua New Guinea (latitude 6 degree S, 1987-1996). Notably, regardless of the rate of its completeness, the temporal dynamics of admissions was preserved over the years, however, neither raw data nor results on further analyses about eventual inter-annual cyclic components (periods T&gt;1 year) were provided despite obvious graphical patterns for such a specific time structure (chronome). Interestingly, in a recent analysis by Gomez-Elipe et al (2007) on monthly malaria notifications in Burundi, at almost the same latitude (province of Karuzi, &gt;3 degree S, 1997-2001), the data have shown neither trend not periodic oscillations beyond a 6-month (0.5-year) period. Since the graphical representation of both data sets have indicated an eventual existence of inter-annual variations, and because both are located at the same latitude zone, we have further analyzed the data from Burundi for such periodic oscillations. By using a periodogram regression analysis, we discovered a multicomponent cyclic chronome with periods above 12 months (T=17.5-18.0, 27.5 and 65.0-65.5 months, all at p&lt;0.05). Notably, the most strong cyclic pattern at p&lt;0.002 in the periodogram of the detrended malaria rates in Burundi remained only that with a peak at about 1.5 years (period T=17.5-18.0 months, R=0.51, z=5.3). It is possible that likely inter-annual cyclic patterns might exist also in the time structure for cerebral malaria admissions in Papua New Guinea and, if confirmed, these may be found very useful in epidemic forecasting and programs implementation. We explored these cyclic variations and also discussed possible associations with environmental factors exhibiting alike cyclicity.

Completeness of malaria notification in the Netherlands 1995-2003 assessed by capture-recapture method

In 1999 in the Netherlands, the duty to notify malaria was transferred from physicians to laboratories by the new Infectious Diseases Law. To evaluate the effect of this change, we aimed to estimate completeness of malaria notification in the Netherlands from 1995-2003. We calculated it relative to sentinel laboratory and hospital admission data. Using the two-source capture-recapture method (CRM), we estimated the total number of cases to assess the completeness relative to this number. The completeness of notification relative to sentinel data was 18.2 % (95% CI of 15.7-20.7) from 1995-1998 and 56.4 % (95% CI of 47.0-65.8) for 2000-2003. The completeness relative to the number of malaria cases admitted to the hospital was 35.1 % for the period 1995-2003. The estimated numbers of cases of malaria between 1995 and 1998 were 3123 (95% CI of 2796-3449) and 5043 (95% CI of 4343-5742) between 2000 and 2003. The completeness relative to this numbers changed from 35.5 % (95% CI of 32.1-39.7) in 1995-1998 to 36.1 % (95% CI of 31.7-41.9) for the years 2000-2003. Laboratory-based notification has significantly increased the absolute number of malaria notifications, but there was no change in completeness relative to hospital admissions. The increase in estimated malaria cases may be artificial, due to the extent of violation of CRM requirements over the study period.

Notifications of imported malaria in Western Australia, 1990–2001: incidence, associated factors and chemoprophylaxis

To assess changes in and factors associated with recent malaria notifications in Western Australia (WA). Retrospective analysis of the WA Notifiable Infectious Diseases Database and enhanced surveillance questionnaires completed by attending medical practitioners. Cases of malaria notified between January 1990 and December 2001. Annual notifications by demographic variables (including age, sex, occupation and place of residence), region/country of acquisition, chemoprophylaxis used, Plasmodium species and outcome. 482 patients were notified (mean age, 31 years; 80% male); 57% lived in Perth, 31% in country areas and 12% in an immigration detention centre. Comparison between the 6-year periods 1990-1995 and 1996-2001 showed that Plasmodium falciparum cases increased from 29 (14%) to 108 (44%; P < 0.001), while Plasmodium vivax cases decreased from 157 (77%) to 122 (50%; P < 0.001); immigrants in detention, defence force personnel and cases from Africa were increasingly represented (P < 0.05 in each case). Only 31% of patients took regular chemoprophylaxis and, among these, the regimen was appropriate in only a quarter. There was a median period of 3 days between symptom onset and diagnosis. One patient died. There has been an increase in P. falciparum cases in WA since 1990. This reflects the influx of immigrants in detention, deployment of military personnel to East Timor and increasing numbers of cases from Africa. A significant number of Australian travellers who developed malaria had not taken chemoprophylaxis either regularly or at all, and, of those who had, the regimen was inadequate in most.

Malária induzida no estado de São Paulo, Brasil

A review is presented of 58 induced malaria cases diagnosed in the São Paulo State, from January 1983 to July 1990. These cases represent 0.3% of the malaria notifications. The parameters sex, age, parasitaemia, clinical symptoms, clinical course and mean time interval between disease onset and diagnosis were studied in 25 blood-transmitted cases and 28 related to sharing needles. Plasmodium vivax was diagnosed in 79.4% and in 5.6% Plasmodium vivax and Plasmodium falciparum were seen. Lower mean age (p < 0.005) in intravenous drug users when compared in the blood-transmitted group were observed. The former also had a mean time interval between disease onset and diagnosis (33.6 days) and patients with blood-transmitted disease (20.6 days). No statistical significant differences were observed (p > 0.10). Even though few induced malaria cases have been diagnosed in São Paulo, State, and considering that blood-transmitted malaria is now under control, the occurrence of malaria due to sharing needles among intravenous drug users should be regarded as a risk for the reintroduction of the disease in malaria--free areas of São Paulo State.