Scale-free dynamics of COVID-19 in a Brazilian city.

A common basis to address the dynamics of directly transmitted infectious diseases, such as COVID-19, are compartmental (or SIR) models. SIR models typically assume homogenous population mixing, a simplification that is convenient but unrealistic. Here we validate an existing model of a scale-free fractal infection process using high-resolution data on COVID-19 spread in São Caetano, Brazil. We find that transmission can be described by a network in which each infectious individual has a small number of susceptible contacts, of the order of 2-5. This model parameter correlated tightly with physical distancing measured by mobile phone data, such that in periods of greater distancing the model recovered a lower average number of contacts, and vice versa. We show that the SIR model is a special case of our scale-free fractal process model in which the parameter that reflects population structure is set at unity, indicating homogeneous mixing. Our more general framework better explained the dynamics of COVID-19 in São Caetano, used fewer parameters than a standard SIR model and accounted for geographically localized clusters of disease. Our model requires further validation in other locations and with other directly transmitted infectious agents.

Prognostic factors and treatment of penetrating gunshot wounds to the head.

BACKGROUND: In an attempt to evaluate the predictive factors of morbidity and mortality in patients who suffered from civilian gunshot wounds to the head, we reviewed a series of 319 patients admitted to the Hospital Santa Marcelina, São Paulo, Brazil, between 1994 and 2000. METHODS: Clinical and cranial computed tomography (CT) results are described. The initial Glasgow Coma Scale (GCS), the presence of an unilateral dilated pupil or medium fixed pupils, and five different findings in the CT scan were considered as variables. The Qui-Square Fisher test was utilized to verify the correlation between the presence of the variables and the occurrence of an increased mortality rate and of an unfavorable outcome (Glasgow Outcome Scale = 2 and 3). RESULTS: In 265 cases the missile penetrated the dura (83%). In our study there was a significant correlation between the low GCS scores on admission and a higher mortality (p < 0.001). This kind of correlation was also noted with patients admitted with unilateral dilated pupil and medium fixed pupil. There were 187 patients (70.5%) evaluated by CT scan. There was a significant correlation between the presence of transventricular or bihemispheric central type trajectory and high mortality. The patients admitted with unilobar supratentorial wounds resulted in better outcome when compared to those with bilobar or multilobar wounds (p < 0.001). A group of 156 patients was submitted to an aggressive surgical protocol. The best results were seen in patients admitted with initial GCS score higher than 8. CONCLUSIONS: We conclude that low GCS scores at admission, unilateral dilated pupil or medium fixed pupil, transventricular or bihemispheric central type trajectory, and bilobar or multilobar wounds noted through CT scan are predictive factors of high morbidity and mortality in patients with gunshot wounds to the head, in our clinical experience. We also conclude that surgical treatment is not recommended for patients with penetrating wounds and GCS score of 3 to 5 in the absence of hematoma causing a mass effect.