The Zika outbreak may have already reached its peak in Brazil, but the threat still looms over the United States, a new study suggests.

In late 2015, the mosquito-borne infection known as Zika virus hit several Latin American countries, including Brazil, where the epidemic ballooned and resulted in thousands of microcephaly cases.

Today, a report by the Imperial College London says the Zika virus outbreak may have peaked in Brazil, with fewer infections and birth defect cases being recorded.

In fact, cases of Zika surged to 8,000 in March this year, but have declined steadily to no more than 200 a week, researchers say.

Neil Ferguson, an expert on infectious disease outbreaks from Imperial College London, says it is possible that the Zika crisis is burning itself out in the Latin American country.

Ferguson, the co-author of the new report, says a large proportion of the population is surviving the infection and becoming immune to it. The epidemic is likely "more than halfway through" and is on its way out of Brazil, he says.

Preventing The Spread Of Zika

In February, the United Nations declared the Zika virus as a "public health emergency of international concern."

Countries across Latin America sent out sanitation workers and soldiers to combat mosquitoes. Officials have urged women to delay or avoid pregnancy because of the virus' link to microcephaly.

However, the new report says trying to stop the spread of Zika virus in Latin America is "pointless" because it may fizzle out on its own within three years.

It also concluded that efforts to prevent the spread of Zika are futile because those methods have not eliminated other mosquito-borne diseases including dengue fever, which is transmitted by the same vector.

Indeed, the study argues that the Zika virus is not "containable" and will fade away on its own once people develop antibodies against it.

Ferguson says the explosive epidemic in Latin America will burn itself out because of a phenomenon known as "herd immunity."

He says because Zika cannot infect the same person two times, the epidemic may reach a stage where there few people left to infect for it to be sustained.

Still, Ferguson says this does not mean that the disease will be completely eliminated.

Even if it fades for a brief period, it may still appear among children who have never been infected. This explains why some viruses such as chickenpox tend to appear during childhood.

Not Everyone Is Convinced

Some experts say that the plummeting number of Zika cases may only be due to the changing seasons in the Southern Hemisphere.

Michael Osterholm from the University of Minnesota says the Southern Hemisphere is nearing winter, which could make the mosquitoes less active.

But Ferguson says even if the virus returns during spring, the infections are least likely to be as numerous as the first time the virus hit Brazil.

Outbreak In The United States

Meanwhile, health officials are worried that the Zika virus may spread in the United States. Reports have shown that more than 1,100 people have already been infected by Zika, mostly while they were traveling abroad.

The good news, according to the Centers for Disease Control and Prevention (CDC), is that mosquito carriers of the infection are not spreading the virus on the mainland.

Americans' use of window and door screens, plus the use of air conditioning, may help prevent massive outbreaks and reduce the number of people exposed to mosquito bites, the CDC said.

Photo: National Institute Of Allergy And Infectious Diseases | Flickr