86. According to the passage, the following are all incorrect EXCEPT ____.

1. avian influenza was not recognized until more than 100 years ago
2. infection with avian influenza cause mild epidemics in birds
3. not all birds are susceptible to infection with avian influenza
4. the disease of avian influenza occurs worldwide except in Italy

87. Characters of the highly pathogenic avian influenza include EXCEPT ____.

1. sudden onset
2. resistance to infection
3. severe illness
4. rapid death

88. Migratory waterfowl are the most resistant to the infection with avian influenza ____.

1. when they would migrate to the south from the north
2. if they do not migrate to the rest of the planet
3. when they are mixed with domestic poultry and pigs
4. while domestic poultry are particularly susceptible to epidemics of avian influenza

89. Control of the outbreak requires EXCEPT.

1. destruction of infected or potentially exposed flocks
2. the quarantining of infected farms
3. the absence of prompt control measures
4. stringent sanitary measures on farms

90. From the passage we can infer that rapid mutation of low to highly pathogenic viruses ____.

1. has led to evolution of the highly fatal form H5N2 viruses
2. makes it impossible for scientists to develop more effective vaccines against the viruses
3. helps to prevent spread from farm to farm by mechanical means
4. proves to be protective of the extensive reservoirs

(Reference keys.)