In another grim reminder that healthcare workers are on the frontlines against emerging infections, an outbreak of Lassa viral hemorrhagic fever in Nigeria has infected 14 medical staff and killed four of them.

In this century thus far, healthcare workers have faced multiple emerging infections, including severe acute respiratory syndrome (SARS), pandemic flu, Ebola, and Middle Eastern Respiratory Syndrome (MERS).

Nigerian health officials reported Lassa fever totals for 2018 as of Feb. 11: 615 suspected cases and 57 deaths. Of those, there have been 193 confirmed cases and 43 confirmed deaths due to Lassa, a virus endemic to rats in the region. Infected humans can transmit the virus through blood and other body secretions. Lassa transmission can be stopped by personal protective equipment (PPE), but the 28% mortality rate in Nigerian healthcare workers underscores the risk of breaks in protocol and/or the lack of adequate PPE.

Meanwhile, three healthcare workers in Saudi Arabia were asymptomatically infected with the MERS coronavirus in a hospital outbreak in January. Other healthcare workers have experienced severe and even fatal infections since the novel emerged in the Middle East in 2012. There have been 2,160 laboratory-confirmed cases of MERS, including 773 associated deaths (36% mortality rate) reported globally, with most of the cases in Saudi Arabia, the World Health Organization reports. The coronavirus is endemic in the camel population in the kingdom.

Will Zika Return?

Employee health professionals were warned of the personal and occupational risks of Zika in 2015-16, with the infections in the U.S. including transmission via a needlestick.

In addition, concerns were raised in 2016 with the strange case of a 73-year-old hospitalized patient in the U.S. who apparently transmitted Zika to a family caregiver — possibly through tears — before dying with an incredibly high level of circulating virus in the blood.1 The secondary case developed symptomatic Zika infection, but subsequently recovered. It is possible that hormonal treatment for prostate cancer somehow accelerated viral replication in the index case, investigators concluded.

Zika has faded back dramatically since arising in Brazil in 2015, but a virus that can cause devastating birth defects is still a threat to re-emerge. As cases declined, the CDC shut down its emergency response to Zika last year. While the virus is in retreat, the CDC still warns pregnant women against traveling to Brazil and other areas in South America and the Caribbean. (See CDC map at: http://bit.ly/2m50Lf7.) Also, men who travel to such areas are advised to either abstain from sex or use condoms for at least six months upon return.

“It is still on our radar, but we do not expect to see additional large outbreaks in the next couple of years — somewhere in that time frame,” said Tyler Sharp, PhD, a CDC epidemiologist and Zika outbreak investigator in Puerto Rico. “That becomes relevant to the U.S. because a very large majority of infections that occur here are imported.”

The Zika virus is primarily spread by female Aedes aegypti mosquitoes, which have a broad range in the U.S. in the summer months. If the virus reaches a human fetus, particularly during the first trimester of pregnancy, it can cause horrific birth defects such as microcephaly.

Though several lines of research are underway, the lack of an approved vaccine gives Zika an opening to resurge in a susceptible population. The question now is whether it can simmer quietly and strike again when enough susceptible people accumulate in an area where A. aegypti live, which unfortunately includes broad swathes of the country in the warmer months.

There were 261 Zika virus infections in returning travelers in 2015 in the U.S., but the outbreak exploded to more than 5,000 cases the following year. Overall, 2016 saw 5,102 symptomatic Zika cases in the U.S., with 4,830 cases in travelers returning from affected areas. There were 218 cases of mosquito-borne transmission in Florida and six cases in Texas in 2016. There were 46 cases of sexual transmission, including one from a female to a male.

From Jan. 1 to Dec. 20, 2017, the CDC reported 385 symptomatic Zika virus disease cases in the U.S. Of those, 378 were in travelers returning from affected areas. There were three cases of local transmission by mosquitoes in the U.S. in 2017, with two in Texas and one in Florida. In addition, there were four cases of Zika acquired via sexual transmission last year in the U.S.

REFERENCES

1. Swaminathan S, Schlaberg R, Lewis J, et al. Correspondence: Fatal Zika Virus Infection with Secondary Nonsexual Transmission. New Engl Jrl Med 2016;375(19):1907-1909.

2. CDC. Zika virus. Available at: http://bit.ly/2kvWeQD.