Biomedical subjects

Luiz Fernandes Lopez

Publications and source records attributed to Luiz Fernandes Lopez.

3 recordsLinked to original sources

PubMed2006

The 1918 influenza A epidemic in the city of São Paulo, Brazil.

The 1918 pandemic H1N1 outbreak in the city of São Paulo is revisited. The outbreak lasted for 10 weeks and reached 116,771 officially recorded cases amongst 523,194 inhabitants. The total number of deaths summed up to 5331, with a lethality rate of 4.5% and an overall mortality rate of around 1%. We propose a mathematical model that tallies available data with good accuracy and allows the estimation of the basic reproductive number, R(0). The model showed a remarkably good accuracy in retrieving the real data from São Paulo city outbreak considering the total number of recorded cases and deaths and the timing of the outbreak. The basic reproduction number calculated of 2.68 can be compared to estimates carried out for other flu strains, like the estimates for H3N2, whose values ranged from 1.5 to 2.5. We hypothesize that the Southern parts of the world in which there was relatively little impact of the Great War, like South America, suffered a much lower H1N1 influenza mortality as compared with that reported for the Northern hemisphere heavily affected by the I World War.

Brazil↗

PubMed2003

Dengue and the risk of urban yellow fever reintroduction in São Paulo State, Brazil.

OBJECTIVE: To propose a mathematical method for the estimation of the Basic Reproduction Number, R0, of urban yellow fever in a dengue-infested area. METHODS: The method is based on the assumption that, as the same vector (Aedes aegypti) causes both infections, all the quantities related to the mosquito, estimated from the initial phase of dengue epidemic, could be applied to yellow fever dynamics. It is demonstrated that R0 for yellow fever is, on average, 43% lower than that for dengue. This difference is due to the longer dengue viremia and its shorter extrinsic incubation period. RESULTS: In this study the analysis was expanded to the epidemiological situation of dengue in S o Paulo in the year 2001. The total number of dengue cases increased from 3,582 in 2000 to 51,348 in 2001. It was then calculated R0 for yellow fever for every city which have shown R0 of dengue greater than 1. It was also estimated the total number of unprotected people living in highly risky areas for urban yellow fever. CONCLUSIONS: Currently there is a great number of non-vaccinated people living in Aedes aegypti infested area in the state of São Paulo.

Aedes↗

PubMed2002

Threshold conditions for infection persistence in complex host-vectors interactions.

As classically defined by Macdonald in the early 1950s, for the case of diseases with one vector and one host, the Basic Reproduction Number, R0, is defined as the number of secondary infections caused by a single infective of the same type (vector or host) during its infectiousness period in an entirely susceptible population. In the case of a disease which has one vector and one host, it is easy to show that R0 coincides with the threshold for the establishment of an endemic state: if R0 > 1 (< 1), the disease can invade (cannot invade) the host population. In this paper we examine various epidemic situations in which there are more than one vector and/or host. We show that in those more complex systems it is not possible to deduce a single R0 but rather a threshold for infection persistence which is a composite of several quantities closely related to the classical expression of R0. Another definition of R0 given by Diekmann, Heesterbeek and Metz, and denoted in this paper R0NGO is discussed and applied as an alternative to calculate the thresholds for infection establishment.

Animals↗