**6. Epidemiological characteristics of FMD epidemics**

Throughout the seven epidemics occurred since 2000, pig and cattle were the main species affected by FMD outbreak. The main factors of virus transmission were associated with the movement of vehicles, behaviors of people, and distribution of materials rather than move‐ ment of animals. Epidemics started in winter were usually long and large. The cold and dry winter climate in Korea made favorable condition for surviving FMD virus. In addition, low temperature during the winter might have preserved FMD virus for longer periods. Disin‐ fecting farms, vehicles, and tools wasn't effective because the low temperature let disinfectants freeze. The hygiene status of livestock farms remained poor and animal disease could spread widely and rapidly. Epidemics of the 2010/2011 and 2014/2015 were the cases.

#### **6.1. Characteristics of epidemic in 2002**

The index case of the 2002 epidemic was notified on 2 May 2002. The next day, on 3 May, the second outbreak was notified at a pig farm in 25 km away from the index case. Based on the epidemiological investigation, FMD virus was probably spread from the index case to the second outbreak farm by a salesperson of a veterinary pharmaceutical company. Subsequently developed two spatial clusters centered of these farms and all known outbreak farms were encompassed except for one case. Genetic analysis of virus isolates from all of 15 outbreak farms, except for one from which no viral isolate was obtained, suggested that they had originated from a single common source. Herd serial interval of disease transmission at farm level was 8–9 (average ± standard deviation, 9.1 ± 2.0, median 8.5) days, and the transmission was extended into five generations. Eight farms were already infected before detecting the index case. A study on simulation modeling on various control strategy for the epidemic in 2002 suggested that the prompt implementation of control measures is the most effective in reducing both size and duration of future outbreaks [14].

#### **6.2. Characteristics of epidemic in January 2010**

The index case farm for the epidemic of January 2010 employed a foreigner, entered Korea on October 2009, as a farm hand. Disinfection or other biosecurity measures had not been taken before starting work on that farm. Furthermore, a parcel was delivered to the person above‐ mentioned from his country on November 2009. In 2009, countries in northeast Asia had numerous outbreaks reported of FMD serotype A. Considering these findings, employment of a foreign worker in the first outbreak farm was identified as a possible route of virus introduction into Korea. FMD virus was subsequently transmitted to other farms through local veterinarian's examination, farmers' meeting, and farm owner's visit to the infected area [15]. The honest report of the local veterinarian his visiting places allowed to detect potential infections in early stage then promptly implement control measures. Unlikely to other epidemics during winter, heavy snow of early January 2010 in the outbreak area helped to restrict moving vehicles. So the spread of virus could be minimized.

#### **6.3. Characteristics of epidemic in April to May 2010**

**6. Epidemiological characteristics of FMD epidemics**

widely and rapidly. Epidemics of the 2010/2011 and 2014/2015 were the cases.

**6.1. Characteristics of epidemic in 2002**

reducing both size and duration of future outbreaks [14].

restrict moving vehicles. So the spread of virus could be minimized.

**6.2. Characteristics of epidemic in January 2010**

Throughout the seven epidemics occurred since 2000, pig and cattle were the main species affected by FMD outbreak. The main factors of virus transmission were associated with the movement of vehicles, behaviors of people, and distribution of materials rather than move‐ ment of animals. Epidemics started in winter were usually long and large. The cold and dry winter climate in Korea made favorable condition for surviving FMD virus. In addition, low temperature during the winter might have preserved FMD virus for longer periods. Disin‐ fecting farms, vehicles, and tools wasn't effective because the low temperature let disinfectants freeze. The hygiene status of livestock farms remained poor and animal disease could spread

12 Epidemiology of Communicable and Non-Communicable Diseases - Attributes of Lifestyle and Nature on Humankind

The index case of the 2002 epidemic was notified on 2 May 2002. The next day, on 3 May, the second outbreak was notified at a pig farm in 25 km away from the index case. Based on the epidemiological investigation, FMD virus was probably spread from the index case to the second outbreak farm by a salesperson of a veterinary pharmaceutical company. Subsequently developed two spatial clusters centered of these farms and all known outbreak farms were encompassed except for one case. Genetic analysis of virus isolates from all of 15 outbreak farms, except for one from which no viral isolate was obtained, suggested that they had originated from a single common source. Herd serial interval of disease transmission at farm level was 8–9 (average ± standard deviation, 9.1 ± 2.0, median 8.5) days, and the transmission was extended into five generations. Eight farms were already infected before detecting the index case. A study on simulation modeling on various control strategy for the epidemic in 2002 suggested that the prompt implementation of control measures is the most effective in

The index case farm for the epidemic of January 2010 employed a foreigner, entered Korea on October 2009, as a farm hand. Disinfection or other biosecurity measures had not been taken before starting work on that farm. Furthermore, a parcel was delivered to the person above‐ mentioned from his country on November 2009. In 2009, countries in northeast Asia had numerous outbreaks reported of FMD serotype A. Considering these findings, employment of a foreign worker in the first outbreak farm was identified as a possible route of virus introduction into Korea. FMD virus was subsequently transmitted to other farms through local veterinarian's examination, farmers' meeting, and farm owner's visit to the infected area [15]. The honest report of the local veterinarian his visiting places allowed to detect potential infections in early stage then promptly implement control measures. Unlikely to other epidemics during winter, heavy snow of early January 2010 in the outbreak area helped to Investigation for the epidemic from April to May 2010 identified possible routes of between‐ farm transmission were mostly associated with livestock related vehicles including contami‐ nated feed‐delivery vehicles, artificial inseminators, and delivery of veterinary pharmaceutics, total mixed ration (TMR) feed. Meetings of livestock‐related people, visits to contaminated regions, vehicle movements, sales agents of animal feed companies, and participants of livestock culling seemed also contributed [15].

#### **6.4. Characteristics of epidemic in November 2010 to April 2011**

In the epidemic from November 2010 to April 2011, the routes of FMD virus introduction and their estimated frequencies for the 152 subsequent outbreaks except for the index case pig‐farming complex were visitors (105, 69.1%), farmers (23, 15.1%), local spread (18, 11.8%), and delivered materials (6, 3.9%). Six outbreak farms, for which virus pathway was attributed to visitors, were associated with treatment or manipulation of artificial in‐ semination, and 14 outbreaks were due to vehicles transporting live animals. The initial contributing factor of the 2010/2011 nationwide FMD epidemic was the regional feature of Andong, Gyeongsangbuk‐do, where the residents were closely related to each other. Dur‐ ing the epidemic, the frequent contacts might help the virus spread rapidly out to adja‐ cent areas. The main cause of the long‐distance virus' spread to the northern Gyeonggi‐do was presumed to be related to the transport of pig manure to be used to installation test of a manure treatment machine. On 17 November 2010, pig manure from the pig complex in Andong was sent to the developer of the manure drying machine in Paju, Gyeonggi‐ do. The FMD virus already had been spread to nearby farms in the northern Gyeonggi‐do area before any preventive measure was taken. The first outbreak in northern Gyeonggi‐ do was occurred on the same day of 14 December 2010 in two farming sites with a large number of pigs, operated by a same owner. Many farms raising cattle or pigs existed nearby, and shared road. Through traffic in front of the farms, the virus spread quickly to nearby areas. The FMD outbreak in the densely located big farms led to difficulties in taking emergency control measures due to the lack of burial sites and slaughter person‐ nel. These caused FMD spread widely [8].

#### **6.5. Characteristics of epidemic in December 2014 to April 2015**

During the outbreak of December 2014 to April 2015, FMD virus was introduced into 185 outbreak farms mostly by vehicles (143 cases, 78.9%), people (23 cases, 10.8%), local spread (16 cases, 8.6%), and movement of animals (3 cases, 1.6%) in the descending order. The pathways for spreading the virus to farms in other counties included (1) visits by vehicles (or drivers) contaminated at abattoirs, (2) vehicles (or drivers) visiting numerous farms, (3) distribution of infected animals to other farms, (4) distribution of feed from a factory affiliated to a large company to farms in various provinces, and (5) operation of two or more farms located in different provinces by one person (or members of the same family or an affiliated company). Meanwhile, delivery of veterinary pharmaceuticals, de‐ livery of semen for artificial insemination, and transport of manure were associated with

transmission within the same county or province. Vehicles and people, responsible for the introduction of FMD virus into farms, were contaminated at abattoirs (75 cases, 40.5%); livestock facilities (93 cases, 50.3%), including feed factories (17 cases, 9.7%); previous out‐ break farms (67 cases, 36.2%); and infected areas (24 cases, 13.0%). FMD outbreaks contin‐ ued for a long time since December 2014 because of the following reasons: (1) The virus continued to replicate among farms where animals were partially slaughtered; (2) the number of subsequent outbreak farms was inversely related to the proportion of FMD vaccine antibodies at county level; (3) control measures were not implemented at proper times Because farmers were reluctant to report suspected cases; and (4) outbreaks began in December, at the beginning of winter, during which the conditions were favorable for virus survival [9].
