Controlling the Ebola virus outbreak at the source in West Africa is the most effective way to decrease international risk of transmission, according to a research paper. If the epidemic  persists and grows, it's likely there will be more cases  of the deadly virus exported to other countries, including Canada, via air travel, said Dr. Kamran Khan, a physician and researcher at St. Michael's Hospital. Dr. Khan, who examines global airline travel patterns to predict the spread of diseases, said that every month, three Ebola-infected travellers are likely to leave West Africa, which is experiencing a widespread outbreak of the virus -- and this number would only increase as the epidemic grows. Dr. Khan and his co-authors said it is essential that other countries, their public health agencies and hospitals should be prepared. The risk of international spread would be further  _  if this epidemic were to take hold in other countries, especially those with weak public health systems. "The international community must be mindful and be ready to support the early detection and control of cases." Dr. Khan said. Dr. Khan noted that of the almost 500,000 travellers who flew on commercial flights out of Guinea, Liberia or Sierra Leone in 2013, more than half were headed to destinations in five countries: Ghana (17.5 per cent, Senegal (14.4 per cent), the United Kingdom (8.7 per cent, France (7.1 per cent) and Gambia (6.8 per cent). More than 60 per cent of travellers from those countries in 2014 are expected to have final destinations in low- or lower-middle income countries. "Given that these countries have limited medical and public health resources, they may have difficulty quickly identifying and effectively responding to imported Ebola cases", said Dr Khan. In low income countries,   _  .
it is easy to identify imported Ebola cases people have rich medical resources imported Ebola cases may not be effectively responded to travelers are not allowed to go to some places
Question: Controlling the Ebola virus outbreak at the source in West Africa is the most effective way to decrease international risk of transmission, according to a research paper. If the epidemic  persists and grows, it's likely there will be more cases  of the deadly virus exported to other countries, including Canada, via air travel, said Dr. Kamran Khan, a physician and researcher at St. Michael's Hospital. Dr. Khan, who examines global airline travel patterns to predict the spread of diseases, said that every month, three Ebola-infected travellers are likely to leave West Africa, which is experiencing a widespread outbreak of the virus -- and this number would only increase as the epidemic grows. Dr. Khan and his co-authors said it is essential that other countries, their public health agencies and hospitals should be prepared. The risk of international spread would be further  _  if this epidemic were to take hold in other countries, especially those with weak public health systems. "The international community must be mindful and be ready to support the early detection and control of cases." Dr. Khan said. Dr. Khan noted that of the almost 500,000 travellers who flew on commercial flights out of Guinea, Liberia or Sierra Leone in 2013, more than half were headed to destinations in five countries: Ghana (17.5 per cent, Senegal (14.4 per cent), the United Kingdom (8.7 per cent, France (7.1 per cent) and Gambia (6.8 per cent). More than 60 per cent of travellers from those countries in 2014 are expected to have final destinations in low- or lower-middle income countries. "Given that these countries have limited medical and public health resources, they may have difficulty quickly identifying and effectively responding to imported Ebola cases", said Dr Khan. In low income countries,   _  .
A. it is easy to identify imported Ebola cases
B. people have rich medical resources
C. imported Ebola cases may not be effectively responded to
D. travelers are not allowed to go to some places
Answer: