Is the number of syphilis cases in the US the highest in 70 years?

Question

In this article of the Financial Times about a "sexual health crisis" in the US, the following claim is made:

The number of syphilis cases in the US jumped more than a quarter last year to 171,000, the highest level in more than 70 years, according to the Center for Disease Control and Prevention.

Is this statement true, particularly the part about being the highest in 70 years?

The format of this site works best if you stick to one question at a time, which on this site means one notable claim that you're skeptical of. You can always follow up with more claims from the same source as separate questions. — IMSoP, Oct 26 '22 at 20:56
https://skeptics.stackexchange.com/questions/53938/sexual-health-crisis-in-the-usa-claim-2 — An old man in the sea., Oct 26 '22 at 21:47
I have reworded the question to focus more on the claim than the context. — IMSoP, Oct 26 '22 at 21:59
I am automatically skeptical of the _nature_ of the claim. If you're saying that a number in a population is the highest in X years and the population is the biggest it's ever been, then the rate of incidence could have been unchanged for the entire X years and the statement could still be true but meaningless. — jdunlop, Oct 27 '22 at 01:13
https://skeptics.stackexchange.com/questions/53940/has-prep-caused-a-decrease-in-condom-use-amongst-men-who-have-sex-with-men — An old man in the sea., Oct 27 '22 at 10:16
Not sure what the source of your skepticism is here. Do you think the FT is making up numbers, or do you think the statement from the CDC is wrong? — antlersoft, Oct 27 '22 at 14:36

score 9 · Accepted Answer · edited Oct 29 '22 at 20:07

Yes.

This CDC page confirms the 171,074 number.

Owen et al 2022 says

Syphilis is surging in the US, with reported cases climbing 28% last year to 171 074, the highest in three decades, the US Centers for Disease Control and Prevention has reported

(30 years, not 70 years; the FT article is behind a paywall, so I can't see exactly what they said.)

As suggested in the comments, the difference between "highest in 30 years" and "highest in 70 years" depends on whether you're comparing rates (cases per 100,000) or total cases; as shown below, there was a peak of syphilis in 1990 that had slightly higher rates than present, but slightly lower cases than present; prior to 1990, you have to go back to the 1950s to see total syphilis incidence (in numbers rather than rates) comparable to the present level.

I've been digging through the data provided by the CDC at this zip file from the US Centres for Disease Control (I got there by following refs/links from Owen et al. 2022). The file "Syph - Rates by Year 1941-2021.xlsx" has annual rates [which are rates per 100,000; (cases/pop size × 10^5)].

US population data back to 1950 are available from Macrotrends; I added the 1940 census value from Wikipedia and did a little bit of linear interpolation. (The 2021 population value gives a calculated number of cases of 173,554 rather than 171,074, off by about 1% - I wasn't easily able to figure out exactly which set of US population numbers were used to derive the rates in the CDC data set ...)

As far as I can tell, "total" in the data shown here are (primary&secondary) + (early non-primary/non-secondary) + congenital).

Dyer, Owen. 2022. “Syphilis and Gonorrhoea Cases Soar in US.” BMJ 378 (September): o2355. https://doi.org/10.1136/bmj.o2355.

library(readxl)
library(dplyr)
library(cowplot)
library(colorspace)
library(ggplot2); theme_set(theme_bw())
dd <- read_excel("Syph - Rates by Year 1941-2021.xlsx")

## Denominators for rates of reported cases of STDs, excluding
## congenital syphilis, use population estimates from the 
## United States Census Bureau.

uspop <- read.table(header = TRUE, file = "uspop.txt")

pop <- with(uspop,
            approx(year, pop, xout = 1941:2021, rule = 2))
pop2 <- data.frame(Year=pop$x, pop = pop$y)
dd2 <- (full_join(dd, pop2, by = "Year")
    |> mutate(Total = Rate*pop/1e5))

gg0 <- ggplot(dd2, aes(Year, colour = STD)) +
    scale_color_discrete_qualitative(guide=guide_legend(reverse=TRUE))

plot_grid(
    nrow = 1,
    gg0 + geom_line(aes(y=Rate)) +
    labs(main = "Rates per 100,000") +
    theme(legend.position = "none"),
    gg0 + geom_line(aes(y=Total)) +
    labs(main = "Total cases") +
    theme(legend.position = c(0.5,0.5))
)    
ggsave("syph.png", width = 12)

Many thanks for the graph, and the detailed analysis separating rates, from total cases. ;) — An old man in the sea., Oct 30 '22 at 21:54

Is the number of syphilis cases in the US the highest in 70 years?

1 Answers1