Boni Maciej F, Manh Bui Huu, Thai Pham Quang, Farrar Jeremy, Hien Tran Tinh, Hien Nguyen Tran, Van Kinh Nguyen, Horby Peter
Oxford University Clinical Research Unit, Vietnam.
BMC Med. 2009 Sep 3;7:43. doi: 10.1186/1741-7015-7-43.
A novel variant of influenza A (H1N1) is causing a pandemic and, although the illness is usually mild, there are concerns that its virulence could change through reassortment with other influenza viruses. This is of greater concern in parts of Southeast Asia, where the population density is high, influenza is less seasonal, human-animal contact is common and avian influenza is still endemic.
We developed an age- and spatially-structured mathematical model in order to estimate the potential impact of pandemic H1N1 in Vietnam and the opportunities for reassortment with animal influenza viruses. The model tracks human infection among domestic animal owners and non-owners and also estimates the numbers of animals may be exposed to infected humans.
In the absence of effective interventions, the model predicts that the introduction of pandemic H1N1 will result in an epidemic that spreads to half of Vietnam's provinces within 57 days (interquartile range (IQR): 45-86.5) and peaks 81 days after introduction (IQR: 62.5-121 days). For the current published range of the 2009 H1N1 influenza's basic reproductive number (1.2-3.1), we estimate a median of 410,000 cases among swine owners (IQR: 220,000-670,000) with 460,000 exposed swine (IQR: 260,000-740,000), 350,000 cases among chicken owners (IQR: 170,000-630,000) with 3.7 million exposed chickens (IQR: 1.9 M-6.4 M), and 51,000 cases among duck owners (IQR: 24,000 - 96,000), with 1.2 million exposed ducks (IQR: 0.6 M-2.1 M). The median number of overall human infections in Vietnam for this range of the basic reproductive number is 6.4 million (IQR: 4.4 M-8.0 M).
It is likely that, in the absence of effective interventions, the introduction of a novel H1N1 into a densely populated country such as Vietnam will result in a widespread epidemic. A large epidemic in a country with intense human-animal interaction and continued co-circulation of other seasonal and avian viruses would provide substantial opportunities for H1N1 to acquire new genes.
一种新型甲型H1N1流感病毒正在引发全球大流行，尽管该疾病通常症状较轻，但人们担心它可能通过与其他流感病毒重配而改变毒力。在东南亚部分地区，这种担忧更为严重，因为该地区人口密度高、流感季节性不明显、人畜接触频繁且禽流感仍然流行。
我们开发了一个按年龄和空间结构划分的数学模型，以评估甲型H1N1流感大流行对越南的潜在影响以及与动物流感病毒重配的可能性。该模型追踪家畜饲养者和非饲养者之间的人类感染情况，并估计可能接触到感染人类的动物数量。
在没有有效干预措施的情况下，该模型预测，甲型H1N1流感的传入将导致疫情在57天内蔓延至越南一半的省份（四分位间距（IQR）：45 - 86.5天），并在传入后81天达到高峰（IQR：62.5 - 121天）。对于目前公布的2009年H1N1流感基本再生数范围（1.2 - 3.1），我们估计猪饲养者中感染病例数中位数为410,000例（IQR：220,000 - 670,000），有460,000头猪暴露（IQR：260,000 - 740,000）；鸡饲养者中感染病例数中位数为350,000例（IQR：170,000 - 630,000），有370万只鸡暴露（IQR：190万 - 640万）；鸭饲养者中感染病例数中位数为51,000例（IQR：24,000 - 96,000），有120万只鸭暴露（IQR：60万 - 210万）。在此基本再生数范围内，越南人类感染总数的中位数为640万例（IQR：440万 - 800万）。
在没有有效干预措施的情况下，像越南这样人口密集的国家引入新型H1N1流感病毒很可能导致疫情广泛传播。在一个人畜互动频繁且其他季节性和禽流感病毒持续共同传播的国家发生大规模疫情，将为H1N1流感病毒获取新基因提供大量机会。
