Effects of three-hour restricted food access during the light period on circadian rhythms of temperature, locomotor activity, and heart rate in rats.

The effects of food on biological rhythms may influence the findings of chronopharmacological studies. The present study evaluated the influence of a restricted food access during the rest (light) span of nocturnally active Wistar rats on the 24 h time organization of biological functions in terms of the circadian rhythms of temperature (T), heart rate (HR), and locomotor activity (LA) in preparation for subsequent studies aimed at evaluating the influence of timed food access on the pharmacokinetics and pharmacodynamics of medications. Ten-wk-old male Wistar rats were housed under controlled 12:12 h light:dark (LD) environmental conditions. Food and water were available ad libitum, excepted during a 3 wk period of restriction. Radiotelemetry transmitters were implanted to record daily rhythms in T, HR, and LA. The study lasted 7 wk and began after a 21-d recovery span following surgery. Control baseline data were collected during the first wk (W1). The second span of 3 wk duration (W2 to W4) consisted of the restricted feeding regimen (only 3 h access to food between 11:00 and 14:00 h daily) during the L (rest span) under 12:12 h LD conditions. The third period of 3 wk duration (W5 to W7) consisted of the recovery span with ad libitium normal feeding. Weight loss in the amount of 5% of baseline was observed during W1 with stabilization of body weight thereafter during the remaining 2 wk of food restriction. The 3 h restricted food access during the L rest span induced a partial loss of circadian rhythmicity and the emergence of 12 h rhythms in T, HR, and LA. Return to ad libitum feeding conditions restored circadian rhythmicity in the manner evidenced during the baseline control span. Moreover, the MESORS and amplitudes of the T, HR, and LA 24 h patterns were significantly attenuated during food restriction (p < 0.001) and then returned to initial values during recovery. These changes may be interpreted as a masking effect, since T, HR, and LA are known to directly react to food intake. The consequences of such findings on the methods used to conduct chronokinetic studies, such as the fasting of animals the day before testing, are important since they may alter the temporal structure of the organism receiving the drug and thereby compromise findings.

Effects of a seven-day continuous infusion of L-DOPA on daily rhythms in the rat.

The present study was conducted to evaluate the effect of L-3, 4-dihydroxyphenylalanine (L-DOPA) on the daily rhythms of temperature, heart rate and locomotor activity in rats that received a 7-day continuous infusion. Our results indicate that L-DOPA does not induce a loss of the daily rhythmicity of temperature, heart rate and locomotor activity but modifies the main parameters of these rhythms, e.g. it increased the MESOR (midline estimating statistic of rhythm) of temperature and heart rate and increased the amplitude of temperature but decreased the amplitude of heart rate. Taking into account these results obtained after constant rate delivery, we now plan to investigate the effects of DOPA therapy by changing the time of its administration.

Malaria, cause of ahaptoglobinaemia in Africans.

The lack of serum haptoglobin in Africans has been investigated in the Congo, Central Africa, where HpO prevalence is about 30%. This study shows that it is possible to suppress ahaptoglobinaemia within a few weeks by antimalarial chemoprophylaxis, that it does not occur in protected individuals, that ahaptoglobinaemia reappears at its original incidence levels after interruption of chemoprophylaxis, and that some individuals are more susceptible in relation to Hp2 gene. Malaria is the only significant cause of ahaptoglobinaemia in subjects both with and without detectable parasitaemia. The possible mechanisms involved are discussed.

Malaria transmission in Southern Madagascar: influence of the environment and hydro-agricultural works in sub-arid and humid regions. Part 1. Entomological investigations.

A 4-year entomological study was carried out in Southern Madagascar to identify malaria vectors, evaluate the transmission and compare the influence of irrigation in the sub-arid and adjacent humid regions. Three villages were involved in this entomological survey: Androvasoa (located in the natural sub-arid ecosystem), Pépiniére (sited at the centre of an irrigated rice scheme in the sub-arid region) and Esana (bordered with rice fields in the humid region). Mosquitoes were collected inside and outside dwellings when landing on human beings, with light traps and with knockdown indoor sprays. Anopheles arabiensis, Anopheles merus and Anopheles funestus were found in every village while Anopheles gambiae s.s. was only found in the village bordering the rice-fields (Pépiniére) and Anopheles mascarensis, a mosquito native to Madagascar, was only found in the humid region (Esana). In Pépiniére, the annual entomological inoculation rate (EIR) was low (EIR=0.4 infective bites/man/year (IBM)). In the irrigated scheme of the sub-arid region, malaria transmission was 150 times higher (mean EIR=63 IBM) than in the natural ecosystem and A. funestus was the main vector, responsible for 90% of infective bites. In Esana, the level of malaria transmission was high (EIR=41 IBM) and 2/3 of the infective bites were due to A. mascarensis, despite the presence of A. gambiae s.s. and A. funestus. These results are discussed with reference to the impact of irrigation on malaria in Africa ("the paddies paradox").

Indoor resting by outdoor biting females of Anopheles gambiae complex (Diptera:Culicidae) in the Sahel of northern Senegal.

Three villages in the Senegal River basin were selected to study the biting and resting behavior of Anopheles gambiae s.l. in relation to human habits, rainfalls, and rice culture irrigation. All inhabitants sleep outside throughout the year, mainly under poor quality bednets. Mosquitoes were collected host-seeking during the night on human bait outside and resting during the day inside and outside in pit shelters. An. gambiae s.s. and An. arabiensis fed mainly outside, the only place where hosts are available; fed and gravid females resting indoors fed outside. The proportions of An. gambiae s.s. and An. arabiensis in outdoor biting catches and in indoor spray catches were not significantly different, but they differed from year to year with the latter sampling method, An. gambiae s.s. predominated in 1990, a more wet and humid year, whereas An. arabiensis was more common in 1991, which was an arid year. Both species are highly endophilic in this arid area where outdoor-resting places are limited.

Airport malaria : a rare disease still poorly understood.

The article by Daniel Lusina and colleagues in this issue of Eurosurveillance is a timely reminder of the dangers of airport malaria. Since 1977, when the disease was first documented, 75 cases of airport malaria have been observed in western Europe, 28 o

Diversity of malaria in rice growing areas of the Afrotropical region.

It is well known that 'in many instances the rice agrosystem perfectly fits the ecological requirements of pathogens or vectors' and in fact 'malaria, schistosomiasis and Japanese encephalitis are important vector-borne diseases associated with rice production in developing countries' (IRRI, 1987). In spite of these fears, rice cultivation has been on the increase in the African region in response to demographic and economic pressures. However, although rice fields provide suitable breeding places for Anopheles mosquitoes and rice cultivation leads to an increase in the biting rates, the species which are adapted to these sites are not the same in all parts of Africa. Several examples illustrate this phenomenon: An. funestus in the rice fields of Madagascar, An. pharoensis in saline water rice fields in the delta of the Senegal river, An. arabiensis in northern Cameroon and Burundi, An. gambiae Mopti form in the Kou Valley (Burkina Faso) and An. gambiae Savanna form in the rice fields of Kafine near Bouaké (Côte d'Ivoire). The vectorial capacities of these species are not the same and malaria inoculation rates are not necessarily increased in the riceland agroecosystem. The consequences for malaria of introducing rice cultivation depend on the situation before its introduction: it could be worsened in unstable malaria areas but not in stable malaria areas. Therefore, sound epidemiological and entomological knowledge are needed before causing any environmental modifications for agricultural purposes and there should be regular monitoring to avoid any outbreak.

[Vectors and environmental factors in malaria]. / Vecteurs et facteurs d'environnement du paludisme.

Malaria is a major risk for more than two billion human beings on Earth, and is the cause of 700,000 to 2.5 million deaths per year. The causative factor, Plasmodium (four species), involves an asexual cycle in man and a sexual one in anopheline mosquitoes. The four species of Plasmodium are pathogenic for man but P. falciparum accounts for more than 90% of deaths. Only black Africans are refractory to P. vivax, a characteristic linked to the lack of Duffy antigen. Among the 400 species of anophelines so far recorded, less than 50 are recognized malaria vectors. Every one has its own geographic and ecological characteristics, which locally induce the epidemiological trends and its biodiversity. In a given site transmission depends on competent anopheline species, their infective rate and their biting rate. Inhabitants of endemic areas develop during infancy immunity which protect them during the rest of their lives. This immunity (premunition) between parasite and its host is acquired at an heavy price of infant mortality. It can decrease rapidly when people leave endemic areas. Because inhabitants of endemic areas continue to harbor asymptomatic parasites they become good parasite reservoirs. The diversity of epidemiological situations needs a diversification of malaria control measures. The prognosis of the evolution of malaria depends on control measures, applied or not, and on the evolution of climatic and anthropic environment, which are very hard to predict for the time being.

[The evaluation of the critical levels of malaria transmission in a stable endemic area (author's transl)]. / L'évaluation des seuils critiques de transmission du paludisme en zone d'endémie stable.

During a longitudinal survey done in the degraded forest area south of Brazzaville (People's Republic of the Congo), it appeared that plasmodic index of preschool children was always lower than 50% in spite of an inoculation rate of about one infected bite per child per night all along the year. The actual incidence rate estimated with Muench model was h = 0,015 while the recovery rate was r = 0,032 (i.e. about three times faster than the usual values admitted since Mac Donald work) for young children (0 to 4 years old). A computer study has shown that an incidence of h1 = 0,0012 was enough for the "infection" of children (Ross model) while an incidence of h2 = 0,0014 would induce a situation of superinfection (Dietz et al. model). Therefore the actual incidence was 10 to 12 times higher than the critical values of the incidence rate. To decrease the malaria transmission at a level lower than the critical values i.e. to obtain a reproduction rate below I the calculations and graphs have shown that anopheline density or human gametocytaemia have to be reduced by about 90% while the survival rate of the vectors must be reduced by about 12%. Therefore it appeared that the determination of the critical levels of every parameters of malaria transmission is a needful stage for a better planification of any malaria control programme.

Impact of deltamethrin-impregnated bednets on biting rates of mosquitoes in Zaire.

In a rural area of Zaire, the whole population of a village was protected by deltamethrin-impregnated mosquitoes bednets. A similar village was observed as a control. Biting rates for mosquitoes were recorded in both villages. The principal man-biting species were Mansonia africana, Mansonia uniformis, and Aedes aegypti. In the village protected by the impregnated mosquito bednets, the number of Mansonia bites was reduced 96% indoors and at a lesser rate outdoors. Biting rates of Ae. aegypti dropped to 0 indoors, but the outdoor biting rate remained unchanged. It is concluded that the reduction in mosquito bites is not only caused by the repellent action of the deltamethrin but also by a reduction in mosquito numbers.

Evolution of malaria in Africa for the past 40 years: impact of climatic and human factors.

Different malarial situations in Africa within the past 40 years are discussed in order to evaluate the impact of climatic and human factors on the disease. North of the equator, more droughts and lower rainfall have been recorded since 1972; and in eastern and southern Africa, there have been alternating dry and wet periods in relation to El Niño. Since 1955, the increase in human population from 125 to 450 million has resulted in both expansion of land cultivation and urbanization. In stable malaria areas of West and Central Africa and on the Madagascar coasts, the endemic situation has not changed since 1955. However, in unstable malaria areas such as the highlands and Sahel significant changes have occurred. In Madagascar, cessation of malaria control programs resulted in the deadly epidemic of 1987-88. The same situation was observed in Swaziland in 1984-85. In Uganda, malaria incidence has increased more than 30 times in the highlands (1,500-1,800 m), but its altitudinal limit has not overcome that of the beginning of the century. Cultivation of valley bottoms and extension of settlements are in large part responsible for this increase, along with abnormally heavy rainfall that favored the severe epidemic of 1994. A similar increase in malaria was observed in neighboring highlands of Rwanda and Burundi, and epidemics have been recorded in Ethiopia since 1958. In contrast, in the Sahel (Niayes region, Senegal), stricken by droughts since 1972, endemic malaria decreased drastically after the disappearance of the main vector, Anopheles funestus, due to the destruction of its larval sites by cultivation. Even during the very wet year of 1995. An funestus did not reinvade the region and malaria did not increase. The same situation was observed in the Sahelian zone of Niger. Therefore, the temperature increase of 0.5 degree C during the last 2 decades cannot be incriminated as a major cause for these malaria changes, which are mainly due to the combination of climatic, human, and operational factors.

[Origin of malaria epidemics on the plateaus of Madagascar and the mountains of east and south Africa]. / L'origine des épidémies de paludisme sur les Plateaux de Madagascar et les montagnes d'Afrique de l'Est et du Sud.

The Highlands of Madagascar were malaria free until 1878, when a severe epidemic occurred, following the development of irrigated rice farming. Then, the disease became endemic. Between 1949 and 1962, malaria was "eradicated" on the Highlands by joint house spraying and chemoprophylaxis measures. The main vector An. funestus disappeared. In 1986-1988, a very severe epidemic with high lethality rate devastated the Highlands. It is now under control. Thanks to the data of a religious dispensary, we could follow the evolution of malaria on the Highlands from 1971 to 1995. The number of cases begin to grow in 1975 when the surveillance was neglected. A second step was observed in 1979, when chemoprophylaxis/chemotherapy centres were closed. Then, the increase of malaria became exponential up to 1988. At the time, the prevalence had became similar to that of 1948, before the eradication. The epidemic is not due to global warming because the temperature has been stable for the last 30 years. The malaria rise was due the cancellation of control measures. When control was reactivated, the epidemic ceased. In Swaziland, Zimbabwe and South Africa, malaria epidemics were also due to control failure. In Uganda Highlands, above 1500 m, malaria rise seems linked to the environmental changes, e.g. the cultures which replace papyrus swamp in the valley. But malaria did not overcame the altitude of 1900 which it had already reached in 1960. Rainfall should also be considered as a key factor in the epidemics. In the Sahel West Africa, temperature increased from 0.5 degree C to 01 degree C degree in the last 25 years, but rainfall decreased from 30%. As a result, one of the vector, Anopheles funestus disappeared and malaria prevalence dropped by 60 to 80%. It is not acceptable to predict the future evolution of malaria in taking in account only one parameter: the temperature. The whole factors involved in the epidemiology should be taken into account. The predictions based only on the temperature increase (global warming) can be totally wrong if the rainfall, for example, decreases.

[Historical epidemiology of bancroftian filariasis in southwest islands of the Indian Ocean]. / Epidémiologie historique de la filariose de bancroft dans les îles du sud-ouest de l'Océan Indien.

Bancroftian filariasis arose in the South-West Indian Ocean Islands with human settlements. During the XIXe century, most of the islands were infected but the prevalence and clinical features of the disease were different from an Island to an other. The vectors are Cx. quinquefasciatus, An. gambiae, An. arabiensis, An. funestus. Even if Culex are proven vectors most of the transmission is due to anophelines. The introduction of the parasite was followed by an explosion of the diseases with dramatic clinical features. But since the beginning of the century the disease retreats. Whatever this is due to malaria vector control and specifies chemoprophylaxis or is linked to the rise of life standard is still a subject of debate.

[Anopheles paludis: important vector of malaria in Zaire]. / Anopheles paludis: vecteur important du paludisme au Zaïre.

An entomological study was carried out on the transmission of malaria in the Bandundu region, Zaïre, during the dry season (July and August 1991). Five Anopheles species were recorded: Anopheles paludis, A. gambiae, A. funestus, A. moucheti and A. nili. A paludis was the dominant species and represents 55.1% of the total; the average number of A. paludis bites per man/day was 4.2. The sporozoite index was 6.2%; the inoculation rate due to A. paludis was h = 0.26, 1 infective bite each 4 days. A. paludis plays an important role with A. gambiae and is considered as one of the main vectors of malaria in this region.

[Malaria vector control in Cameroon: past, present, future. Reflections]. / La lutte antivectorielle au Cameroun. Passé-présent-avenir. Réflexions.

During the fifties, large scale malaria vector control projects based upon house spraying were implemented in Southern and Northern parts of Cameroon in line of malaria eradication concept. In the South, the pilot zone of Yaounde gathered about 150,000 inhabitants, in the forest area. First operations started in 1953 but the programme became actually operational in 1956. It was divided in two parts: the western part was treated with DDT, while the eastern one was treated with dieldrin. At the same time, the whole forested area was also treated with dieldrin until 1960. Yaounde itself was not treated because it was free of anopheles and malaria. House spraying in the pilot area of Yaounde was a complete success and plasmodic index dropped below 1%. The same success was observed in most of the southern treated areas. Unfortunatly dieldrin resistance of An. gambiae hampered this programme which stopped in 1960. The northem pilot project dealt with some 250,000 inhabitants around Maroua, in a savanna area. To avoid dieldrin resistance observed in 1956, DDT was selected and house spraying started in 1959. From a strictly operational point of view, the campaign was considered as a success. But after two years, it was noticed that plasmodic index remained still around the same value of 35% and the programme stopped. It was thus stated that according to available techniques it was not possible to reach the ultimate goal of eradication even when chemoprophylaxis (chloroquin + pyrimethamin) was added. The comparison between south (= success) and north (= failure) was very interesting as it underlined the big differences between epidemiological faces, an unaccepted concept at that time. Now ecological and epidemiological diversity is the well acknowledged. It also underlined the need of diversity of strategies according to the epidemiology of the disease and the ecology of its vector Vector control was then stopped for a while. In the eighties, Primary Health Care was promoted and malaria control shifted from vector to parasite control, vector control remaining as a prevention method. But chemioresistance of Plasmodium falciparum appeared and. quickly spread, at different levels, across the country. A new emphasis was therefore given to vector control thank to the newly developed technique of insecticide impregnated mosquito nets. Two kinds of studies were undertaken: - what people were actually doing in term of mosquito control at family level, the main reason and the costs as well as current use of mosquito nets - the efficacy of pyrethroid treated mosquito nets (IMN) in different areas of southern forested area against different malaria vectors: An. gambiae, An. nili, An. moucheti. It thus clearly appeared that IMN were very successful in sharply reducing malaria transmission aAd morbidity. But its promotion is limited by the current poor use of mosquito nets in Yaoundé (1 mosquito net for 27 "beds") while in Douala, where IMN are largely used against the bite of the huge population of Culex. quinquefasciatus, the implementation of the first riational centre for impregnation of mosquito net was a great success, as long as it was headed by a motivated and skill manager Impregnated mosquito nets appear thus as a tool of great efficacy but their sustainability is still matter of concern and promotional campaigns must be developed involving private and public, political and scientific spheres as well as the general population who should be encouraged to become partners and even actors of vector and malaria control at their household level.

[Agriculture-health interface in the field of epidemiology of vector-borne diseases and the control of vectors]. / Les interfaces agriculture-santé dans les domaines de l'épidémiologie des maladies à vecteurs et de la lutte antivectorielle.

This paper is a review of the interactions between agriculture and vector borne diseases. Rain forest clearing makes possible the development of heliophilous species of anophelines and snails leading to an increase of malaria and schistosomiasis in Africa. But in Asia, clearing is a control method against Anopheles balabacensis, an important malaria vector. Clearing of forest galleries is followed by the disappearance of shore-dwelling tsetse flies. Woodcutters and pioneer farmers are contaminated with arbovirus and leishmaniasis when entering in natural sylvatic foci of these diseases. Management of drinking water reduces guinea worm as well as cholera and other diarrhoeal diseases. More over when piped water becomes available people are no more obliged to store drinking water in containers where vectors use to breed. Reservoirs of dams offer large possibilities for the development of mosquitoes including anophelines vectors of malaria and filariasis and of snails hosts of schistosomiasis. The medical importance of these man-made breeding sites depends of the local epidemiological features of the diseases. Dam spillways provide breeding for blackflies and man-made foci of onchocerciasis have been described in West Africa. Irrigation channels mainly when non cleared of vegetation are good breeding places for anophelines and snails. Irrigated surfaces like rice fields are highly productive in anophelines and other dangerous species of Culicinae. Insecticides used in agriculture, mainly to control cotton and rice pests, have been at the origin of insecticide resistance of several anopheline species. On an other hand, sometimes rice pests control lead to the control of rice field mosquitoes until they become resistant, e.g. for Culex tritaeniorhynchus the vector of Japanese encephalitis in South Korea. Many international organizations have emphasized the role of intersectorial collaboration to control man-made vector borne diseases foci. Good planning of the infrastructures (e.g. twin spillways) and adequate maintenance are essential. Vector control in rice field is a puzzling question. Wet irrigation was a hope but it cannot be done everywhere. Biological control methods have not been proven to be very efficient. Even Bacillus thuringiensis H14 and B. sphaericus have severe limitation. New tools for intersectorial activities should be a goal for scientists imagination.

[Introduction of onchocerciasis in Central America: the role of the French expeditionary corps to Mexico (1861-1867)]. / L'introduction de l'onchocercose en Amérique centrale: le rôle du corps expéditionnaire français au Mexique (1861-1867).

Close relationships between American and African strains (from savanna) of onchocerciasis have been confirmed by biochemical analysis. It is admitted that the parasite could have been introduced by slave trade. But in Mexico, Torroela supported the hypothesis that onchocerciasis was introduced by Nubian soldiers of the French troops between 1861 and 1867. Some of the 600 soldiers of the Egyptian bataillon, included in the French expeditionnary corps, could have been onchocerciasis carriers. But these troops caserned in Vera Cruz remained in the littoral plain and have not been in contact with the Oxoaca focus of onchocerciasis. It is very unlikely that they can have been at the origin of the disease focus.

[Epidemiological stratification of malaria in the Comoro archipelago]. / Stratification épidémiologique du paludisme dans l'archipel des Comores.

In the Comoros Islands, the level of malarial endemicity varies greatly from one island to the other, even though the total area (4 islands) covers less than 2,300 km2 and has a population of some 600,000 people only. The epidemiological stratification is based on the diversity of human and physical characterisation. They both determine the presence and the behaviour as well as the size of the vector's populations. Vectorial dynamics can explain varying levels of endemicity given parasitological indicators and specific morbidity. Analyzing these criteria shows up different epidemiological features and serves as a basic guideline for malaria control. The efficiency of this control depends on the relationships between the intensity and the length of the transmission, in the framework of protection mechanisms; it is of crucial importance for clinical treatment. Further elements are the age of the patient, the season and the geographic situation of the area. Stratification provides explanations for these relationships and helps to define antimalarial programmes adapting to each situation a range of therapeutic and antivectorial methods. The availability and accessibility of anti-malarial medicine is the minimum requirement for reducing mortality: domestic spray insecticides for reducing transmission are effective for several years and should be followed by the use of mosquito nets or curtains impregnated with pyrethrinoids, and in the particular case of Grande Comore, the use of larvivorous fish. As anywhere else, the economic development, which is dependent on political stability, is the essential basis for malaria control.

[Impact of antivectorial control on malarial morbidity and mortality in a health district of the Madagascar highlands]. / Impact de la lutte antivectorielle sur la morbidité et la mortalité palustres dans un district sanitaire des Hautes Terres de Madagascar.

After the dramatic increase of malaria infections from 1985 to 1988 in the Highlands of Madagascar, the vector control programme was reactivated. In order to evaluate the impact of this strategy in the district of Arivonimamo, we have analysed the morbidity and the mortality data collected in all the health care centers of this district. Since 1988, extensive residual house spraying has been carried out on a yearly basis in the eastern part of this district whereas the western part was not included in this spraying programme. Data from each area were compared. In the eastern part, a dramatic decrease of morbitity and mortality related to malaria was observed, the benefit was 69% of expected simple cases, 87% of expected serious cases and 40% of expected deaths due to malaria. It has to be noted that only presumptive cases have been reported since no laboratory facilities are available in these health centers. Nevertheless such findings provide strong support to the continuation of the spraying programme, maybe in a less intensive way, together with an accurate epidemiological surveillance.

[The progress of malaria in sahelian eastern Niger. An ecological disaster zone]. / Evolution du paludisme dans l'est sahélien du Niger. Une zone écologiquement sinistrée.

The south eastern part of the Republic of Niger was ecologically damaged by the dryness since 1971. Rainfall decreased by 30 to 40% as compared to 1961-70 and lake Chad retreated 100 km to the south. Now it does not reach any more the Republic of Niger. Malaria studies have been carried out in urban and suburban places in Zinder and in the Diffa area at the extreme east. In Zinder parasitic indexes (PI) after the rainy season were around 30% to 10% according to the situation of the corner in respect with surface waters during the rains. In dry season the index fell to 3%. In Diffa in a part of the city at high risk because lining the Komadougou river, PI was only 6.7% in October after the rains. Before 1970 PI recorded in Niamey were up to 50%. In Diffa area they were of 49% in N'Guigmi and 32% in Bosso, ecologically similar to Diffa. Obviously there was a sharp decrease of malaria which could be due to the disappearance of An. funestus after 1970. It was one of the main malaria vectors. Its larvae were developing in pools remaining after the rains with heavy standing vegetation. These breeding sites have been destroyed by both dryness and human activities. Now the area has became hypoendemic and is suitable for epidemic because population has not much immunity. A surveillance system for epidemic control should be settle.