Zika infections drastically underreported during 2015 epidemic

Date:
October 1, 2020
Source:
University of Notre Dame
Summary:
More than 100 million infections of Zika virus within Central and
South America and the Caribbean went undetected between 2015 and
2018, according to a new study.



FULL STORY ==========================================================================
More than 100 million infections of Zika virus within Central and
South America and the Caribbean went undetected between 2015 and 2018, according to a new study.


==========================================================================
The University of Notre Dame researchers who conducted the study,
published in PLOS Neglected Tropical Diseases, said the results show
a need for improvements to current infectious disease surveillance
systems. The study also provides insight into the potential severity
of future outbreaks and the current state of herd immunity of Zika in
the West.

"Fewer than 1 percent of cases were actually reported and it shows our surveillance systems catch only a small percentage of actual infections,"
said Sean Moore, research assistant professor in the Department of
Biological Sciences at Notre Dame and lead author of the study. "We
need to think about how to improve surveillance systems to get a better
sense of transmission, especially in cases of diseases that yield a high
number of asymptomatic infections." The first confirmed case of Zika in
the Americas was reported in Brazil in 2015, with infection spreading
rapidly, reaching as far north as Florida and Puerto Rico. In 2016 the
World Health Organization (WHO) declared the epidemic a Public Health
Emergency of International Concern.

The Pan American Health Organization, which serves as an international
agency for the Americas and a regional office of the WHO, totaled
symptomatic infections of Zika at more than 800,000 between 2015 and 2018
-- a number far below the results of the Notre Dame study. Moore's team estimated 132.3 million infections across Latin America and the Caribbean, having collected data from 15 countries and territories in South America, Central America and the Caribbean with a combined total population of
507.1 million.

"There are some similarities to the current situation with COVID-19,"
Moore said. "Between 20 and 50 percent of Zika infections are
asymptomatic. Even when symptoms are present, they tend to be mild, so
if the infection is not severe enough for an individual to seek medical attention, those cases can go undiagnosed." Understanding the scope
of underreporting is particularly important to gain an accurate sense
of herd immunity in the region. Once infected, individuals who recover
from Zika virus are believed to have lifelong immunity, Moore said.

While cases have dropped substantially since 2018, a remaining concern
is the potential for future outbreaks.

"Our research suggests a need for a better understanding of how much transmission is happening within a community," said Moore. "The risk
of congenital birth defects in pregnant women infected with Zika virus
required a separate surveillance system -- testing both the mother
and the baby -- to capture a more accurate indicator of underlying transmission. Without widescale testing and a comprehensive system like
that, we can miss how large an outbreak is in the general population."
A recent study co-authored by Moore and colleagues at Notre Dame found
that gaps in surveillance and limited testing resulted in more than
100,000 coronavirus infections in the United States that went undetected
in the early months of the pandemic.


========================================================================== Story Source: Materials provided by University_of_Notre_Dame. Original
written by Jessica Sieff. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Sean M. Moore, Rachel J. Oidtman, K. James Soda, Amir S. Siraj,
Robert C.

Reiner, Christopher M. Barker, T. Alex Perkins. Leveraging
multiple data types to estimate the size of the Zika epidemic
in the Americas. PLOS Neglected Tropical Diseases, 2020; 14 (9):
e0008640 DOI: 10.1371/ journal.pntd.0008640 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201001113520.htm

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