Use of a mathematical model to estimate tuberculosis transmission risk in an Internet café

<p><b>OBJECTIVE</b>People who live under fragile living conditions may stay overnight in Internet cafés in urban areas. An outbreak of tuberculosis (TB), the routes of which were possibly related to such a facility, has been reported. The purpose of this study was to use a mathematical model to quantify the public health risk of TB infection in such a facility.</p><p><b>METHODS</b>The reproduction number for airborne infection in an enclosed space (R (A)) was estimated using a Wells-Riley model. First, we estimated R (A) for the TB infection based on the report of the TB outbreak in the Internet café. Second, TB infectious dose, number of days of exposure, and air-exchange rate in the facility were varied to estimate the effect of TB risk settings and environmental factors.</p><p><b>RESULTS</b>We assumed that TB patients and 59 susceptible subjects stayed for 150 days in a room where the air-exchange rate was five per hour. Using the estimated median R (A) of 44.14, the TB infection rate was 74.6%. This result was similar to the epidemiological report that the TB infection rate among employees in the Internet café was 70%. The median R (A) increased linearly as the number of days of exposure increased. The slope of the change in median R (A) divided by the change in the number of days of exposure increased exponentially as air-exchange rate decreased; thus air ventilation in a facility may be essential to prevent TB infection.</p><p><b>CONCLUSIONS</b>Appropriate air ventilation in facilities such as Internet cafés is needed as part of a TB-control program in metropolitan areas.</p>

Risk of Transmission of Airborne Infection during Train Commute Based on Mathematical Model

Objective: In metropolitan areas in Japan, train commute is very popular that trains are over-crowded with passengers during rush hour. The purpose of this study is to quantify public health risk related to the inhalation of airborne infectious agents in public vehicles during transportation based on a mathematical model. Methods: The reproduction number for the influenza infection in a train (RA) was estimated using a model based on the Wells-Riley model. To estimate the influence of environmental parameters, the duration of exposure and the number of passengers were varied. If an infected person will not use a mask and all susceptible people will wear a mask, a reduction in the risk of transmission could be expected. Results: The estimated probability distribution of RA had a median of 2.22, and the distribution was fitted to a log-normal distribution with a geometric mean of 2.22 and a geometric standard deviation of 1.53, under the condition that there are 150 passengers, and that 13 ventilation cycles per hour, as required by law, are made. If the exposure time is less than 30 min, the risk may be low. The exposure time can increase the risk linearly. The number of passengers also increases the risk. However, RA is fairly insensitive to the number of passengers. Surgical masks are somewhat effective, whereas High-Efficiency Particulate Air (HEPA) masks are quite effective. Doubling the rate of ventilation reduces RA to almost 1. Conclusions: Because it is not feasible for all passengers to wear a HEPA mask, and improvement in the ventilation seems to be an effective and feasible means of preventing influenza infection in public trains.

Risk of transmission of airborne infection during train commute based on mathematical model

<p><b>OBJECTIVE</b>In metropolitan areas in Japan, train commute is very popular that trains are over-crowded with passengers during rush hour. The purpose of this study is to quantify public health risk related to the inhalation of airborne infectious agents in public vehicles during transportation based on a mathematical model.</p><p><b>METHODS</b>The reproduction number for the influenza infection in a train (R(A)) was estimated using a model based on the Wells-Riley model. To estimate the influence of environmental parameters, the duration of exposure and the number of passengers were varied. If an infected person will not use a mask and all susceptible people will wear a mask, a reduction in the risk of transmission could be expected.</p><p><b>RESULTS</b>The estimated probability distribution of R(A) had a median of 2.22, and the distribution was fitted to a log-normal distribution with a geometric mean of 2.22 and a geometric standard deviation of 1.53, under the condition that there are 150 passengers, and that 13 ventilation cycles per hour, as required by law, are made. If the exposure time is less than 30 min, the risk may be low. The exposure time can increase the risk linearly. The number of passengers also increases the risk. However, R(A) is fairly insensitive to the number of passengers. Surgical masks are somewhat effective, whereas High-Efficiency Particulate Air (HEPA) masks are quite effective. Doubling the rate of ventilation reduces R(A) to almost 1.</p><p><b>CONCLUSIONS</b>Because it is not feasible for all passengers to wear a HEPA mask, and improvement in the ventilation seems to be an effective and feasible means of preventing influenza infection in public trains.</p>

The Use of Docosahexaenoic Acid Supplementation to Ameliorate the Hyperactivity of Rat Pups Induced by in utero Ethanol Exposure

It has been demonstrated that in utero ethanol(EtOH) exposure induces hyperactive behavior and learning disturbances in offspring. In order to investigate the effects of docosahexaenoic acid(DHA) on these neurobehavioral dysfunctions of rat pups induced by in utero EtOH exposure, pregnant Wistar rats were divided into four treatment groups depending on the type of oil added to the diet and drinking water as follows; (a)5% safflower oil with tap water(TW/n−6), (b)3% safflower oil and 2% DHA with tap water(TW/n−3), (c)5% safflower oil with 10%−EtOH(ET/n−6), (d)3% safflower oil and 2% DHA with 10%−EtOH(ET/n−3) at gestational day (GD)7. 10%−EtOH was administered to dams in ET/n−6 and ET/n−3 groups from GD 7 to the pups’ weaning(postnatal week 4), and all pups were fed with the same diet that was given to their dams during the entire examination period. The open−field test and the water E−maze test were conducted for all pups, and a spontaneous motor activity test and the Sidman electric shock avoidance test were performed for some of male pups. Amounts of monoamine metabolites in striatum were then determined, and fatty acid analyses of total brain lipids were performed. The male pups in the ET/n−6 group showed significantly more rearing and square−crossing movements in the open−field test, and significanrly higher spontaneous motor activity during the dark period in the daily cycle compared to the males in the TW/n−6 group. The male pups in the ET/n−3 group showed fewer of these behaviors in the open−field test compared to the ET/n−6 group males, and a normal pattern of spontaneous motor activity. Learning disturbance induced by in utero EtOH exposure was not observed in the E−shaped water maze, but was observed in the avoidance rates in the Sidman electric shock avoidance test. However, there was no significant modifying effect of DHA on the avoidance rates in EtOH exposed pups. The analysis of the fatty acid composition of total lipids in the brains of the pups revealed high levels of DHA in the diet reflected an increased level of brain DHA and caused a decreased level of the brain arachidonic acid. Retroconversion from DHA to eicosapentaenoic acid was also observed. However, there was no significant effect of DHA on the levels of monoamine metabolites. These results support the hypothesis that DHA can counteract the attention deficit hyperactivity disorder.