to 8.2 days) if detection of virus had been used as a substitute for infectiousness. A similar 2016 experiment using serotype A virus exposed susceptible pigs to infected pigs for 8 hour periods and found that pigs were able to spread disease for a full day before developing signs of disease. Analysis of this experimental data estimated the infectious period to be approximately 7 days. Again, the study showed that detection of virus was not an accurate substitution for infectiousness. An accurate understanding of the parameters of infectiousness is an important component of building epidemiological models which inform disease control strategies and policies. Infecting humans Humans can be infected with FMD through contact with infected animals, but this is extremely rare. Some cases were caused by laboratory accidents. Because the virus that causes FMD is sensitive to stomach acid, it cannot spread to humans via consumption of infected meat, except in the mouth before the meat is swallowed. In the UK, the last confirmed human case occurred in 1966, and only a few other cases have been recorded in countries of continental Europe, Africa, and South America. Symptoms of FMD in humans include malaise, fever, vomiting, red ulcerative lesions (surface-eroding damaged spots) of the oral tissues, and sometimes vesicular lesions (small blisters) of the skin. According to a newspaper report, FMD killed two children in England in 1884, supposedly due to infected milk. Another viral disease with similar symptoms, hand, foot and mouth disease, occurs more frequently in humans, especially in young children; the cause, Coxsackie A virus, is different from the FMD virus. Coxsackie viruses belong to the Enteroviruses within the Picornaviridae. Because FMD rarely infects humans, but spreads rapidly among animals, it is a much greater threat to the agriculture industry than to human health. Prevention Like other RNA viruses, the FMD virus continually evolves and mutates, thus one of the difficulties in vaccinating against it is the huge variation between, and even within, serotypes. No cross-protection has been seen between serotypes (a vaccine for one serotype will not protect against any others) and in addition, two strains within a given serotype may have nucleotide sequences that differ by as much as 30% for a given gene. This means FMD vaccines must be highly specific to the strain involved. Vaccination only provides temporary immunity that lasts from months to years. Currently, the World Organisation for Animal Health recognizes