A team of biostatisticians and infectious disease researchers predict the Wuhan 2019n-CoV outbreak will get much worse. (This paper is not yet published; it is a preprint made publicly available for review and commentary by other scientists.)
The team calculated the basic reproduction number of the infection (π π 0) to be 3.6 – 4.0. A basic reproduction number represents how many patients, on average, will be infected by one patient.
The estimated range for 2019n-CoV means that each patient is expected to infect 3.6 – 4.0 other people; therefore 72% – 75% of transmissions must be prevented by disease control procedures for the virus to stop spreading. The diagram shows transmission of cases for π 0 = 4.
Here are the π 0 values of some other diseases for comparison*:
- Ebola 1.5 – 2.5
- SARS 2 – 5
- 1918 Spanish influenza 2 – 3.0
- 2019n-CoV estimated 3.6 – 4.0
- Mumps 4 – 7
- Smallpox 5 – 7
- Measles (one of the most infectious human diseases) 12 – 18
The team also estimated that only 5.1% of infections in Wuhan are identified due to the difficulty in detecting cases of this new disease. (Reporting rates for past outbreaks of MERS and avian influenza are estimated to be 10x to 100x lower than the actual number of cases.) The 2019n-CoV researchers calculated that in 14 days (4 February 2020), the number of infected people in Wuhan may be greater than 190,000 (prediction interval, 132,751 to 273,649).
The model suggests that travel restrictions from and to Wuhan City are unlikely to be effective in halting transmission across China; with a 99% effective reduction in travel, the size of the epidemic outside of Wuhan may only be reduced by 24.9% on 4 February.
Another team calculated a slightly lower π 0 of 2.6 (range 1.5 – 3.5). The incubation period is still unknown but estimates are around 7 days with a range from 2 days to 12 days.
*π 0 is primarily a threshold to indicate whether a disease will become epidemic (π 0 > 1) or will not become epidemic (π 0 < 1); ranges are modeled estimates based on numerous factors and are not ideal comparators. (Wikipedia)
