CDC Expects 'Limited Outbreaks' of Zika Infections in US

Troy Brown, RN


January 28, 2016

A Centers for Disease Control and Prevention (CDC) official said today that "limited outbreaks" of Zika infections are expected in the US, but certain factors may limit the spread of the disease in the states.

Such is not the case in the Americas, though. In a separate briefing earlier today, Margaret Chan, MD, director-general of the World Health Organization (WHO), said, "last year the virus was detected in the Americas, where it is now spreading explosively. As of today, cases have been reported in 23 countries and territories in the region. The level of alarm is extremely high."

Over the next 12 months, she said, as many as 4 million people in the Americas could be infected by the virus.

The Aedes aegypti mosquito — which is responsible for transmitting the virus — is common in some parts of the US, particularly the South. Thus it is possible that the US will have limited outbreaks of Zika virus infection, most likely in the southern states, Anne Schuchat, MD, principal deputy director of the CDC, said in a press briefing.

Urban areas in the US are not as densely populated as some of those in Central and South America, and air conditioning is more widely used in the US. In addition, the US has more widespread mosquito control measures in place. These factors may help limit the disease's spread here, she explained.

"All of the continental US cases to date have been in people who have travelled to a country where mosquitos carrying Zika virus are circulating. We have not yet seen local transmission of Zika in the continental US," Dr Schuchat said.

For this reason, the CDC has issued a travel alert for individuals traveling to areas and certain countries where Zika virus transmission is ongoing. Pregnant women should especially avoid travel to areas where Zika virus transmission is ongoing, because of a strong link between the virus and birth defects.

Although most people infected by the virus have no symptoms at all, the most frequent symptoms of the disease are fever, rash, joint pain, and conjunctivitis. The disease is usually mild, with symptoms resolving within 2 days to 1 week. It usually resolves by itself, and it is uncommon for patients with Zika virus disease to require hospitalization.

But among pregnant women, Dr Schuchat said that authorities in Brazil, where the virus is far more widespread, have "recognized a concerning increase in a usually rare, serious condition among newborns — microcephaly, consistent with the idea that some of these mothers had been infected with the virus early in their pregnancies, potentially harming their developing babies.

"Brazilian health authorities initially reported more than 3500 cases of microcephaly…in the past year, following a major Zika virus outbreak that they experienced," she said.

Lab testing at the CDC strongly suggests a connection between Zika infection and some of these poor pregnancy outcomes, Dr Schuchat explained.

The CDC is also working with public health officials in Brazil to determine whether there is a connection between Zika infection and Guillain-Barré, she said.

Risk "of Alarming Proportions"

In the US, Dr Schuchat said, 31 people in 11 states and Washington, DC, have been infected with the virus (she did not say how many of them were pregnant women).

Zika infections have been confirmed in more than 20 countries in South America and Central America, and a limited number of cases have been reported in Puerto Rico and the US Virgin Islands, she said. "The virus is spreading throughout the Americas and we expect more countries to be affected."

In the Americas, the WHO's Dr Chan said, "the possible links [microcephaly]…have rapidly changed the risk profile of Zika from a mild threat to one of alarming proportions. The increased incidence of microcephaly is particularly alarming as it places a heartbreaking burden on families and communities."

Four factors are particularly concerning to the WHO, she explained: the potential for birth malformations and neurological sequelae, the potential for international spread because of the mosquito, the lack of immunity in newly infected communities, and the lack of a vaccine or treatments for the disease.


There will not likely be a vaccine for the Zika virus in the next few years, Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, said at today's CDC briefing.

Therefore, mosquito control and personal protective measures are advised, including avoiding areas with mosquitos and using approved mosquito repellents.

"We do have a substantial resource commitment for the flavivirus class, so we spend about $97 million on flavivirus research…we will be using the grants that are already out there and immediately supplementing them," he said.

WHO Plans Emergency Meeting February 1

Dr Chan also said this morning that the WHO is convening an International Health Regulations Emergency Committee on the Zika virus and the observed spike in neurological disorders and neonatal malformations on Monday, February 1, in Geneva, Switzerland. The committee will decide whether the Zika virus infection outbreak rises to the level of a Public Health Emergency of International Concern.


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